No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Physiological response to drought stress in Camptotheca acuminata seedlings from two provenances
Abstract and Figures
Drought stress is a key environmental factor limiting the growth and productivity of plants.
The purpose of this study was to investigate the physiological responses of Camptotheca
acuminata (C. acuminata) to different drought stresses and compare the drought
tolerance between the provenances Kunming (KM) and Nanchang (NC), which are
naturally distributed in different rainfall zones with annual rainfalls of 1000–1100 mm and
1600–1700 mm, respectively. We determined relative water content (RWC), chlorophyll
content [Chl(a+b)], net photosynthesis (Pn), gas exchange parameters, relative leakage
conductivity (REC), malondialdehyde (MDA) content and superoxide dismutase (SOD)
and peroxidase (POD) activities of C. acuminata seedlings under both moderate (50% of
maximum field capacity) and severe drought stress (30% of maximum field capacity). As
the degree of water stress increased, RWC, Chl(a+b) content, Pn, stomatal conductance
(Gs), transpiration rate (Tr) and intercellular CO2 concentration (Ci) values decreased, but
water use efficiency (WUE), REC, MDA content and SOD and POD activities increased in
provenances KM and NC. Under moderate and severe drought stress, provenance KM
had higher RWC, Chl(a+b), Pn, WUE, SOD, and POD and lower Gs, Tr, Ci, and REC in
leaves than provenance NC. The results indicated that provenance KM may maintain
stronger drought tolerance via improvements in water-retention capacity, antioxidant
enzyme activity, and membrane integrity.
Figures - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
... Chlorophyll is a photosynthetic pigment with a pivotal role in light absorption during the photosynthesis process . Chlorophyll levels are one of the most common criteria for assessing the severity of drought stress (Ying et al. 2015). Preservation of leaf chlorophyll under stress is one of the physiological characteristics of stress-resistant species (Baiazidi-Aghdam et al. 2016). ...
... Some plants retain their chlorophyll during drought stress, while others lose their chlorophyll (Müller et al. 2010). Drought stress accelerates the decomposition of chlorophyll (Ying et al. 2015;Efeoglu et al. 2009). Chlorophyll depletion under drought stress is mainly due to chloroplast damage by reactive oxygen species (ROS) (Xiao et al. 2008;Schütz and Fangmeier 2001;Faseela et al. 2020) or due to the instability of protein complexes and destruction of chlorophyll by increasing the activity of the chlorophylls (El-Tayeb 2005). ...
Little is known about the potential role of selenium and silicon post drought in plants, and the physiological mechanisms involved are yet to be explored. Medicinal plant cultivation in existing crop systems is of great importance for sustainable production of active ingredients. The first step in this process is to grow the plants under natural field conditions. For this purpose, the effects of drought stress (moderate stress: 25 days without irrigation and severe stress: 40 days without irrigation) and rewatering on physiological traits and photosynthetic pigments of two forest Satureja chemotypes of “carvacrol/thymol/p-cymene” (Darkesh chemotype) and “thymol/p-cymene/carvacrol” (Pono chemotype) were assessed in two separate experiments under foliar application of two drought protectants: selenium (0, 5, and 20 mg/l) and silicon (0, 1, and 5 mM). The results showed that at least in one experiment, the proline content of Darkesh and Pono increased by 33.48 and 16.76% following water stress, respectively. A significant enhancement was observed in proline level only in the Darkesh chemotype by rewatering. In both chemotypes, the sugar content increased (by 11.59 and 27.41%) as water stress increased, respectively. On the other hand, by rewatering, a reduction in sugar content was observed only in the Pono chemotype. Ionic leakage increased in both chemotypes during the second experiment. Similar to sugar content, rewatering decreased ionic leakage only in the Pono chemotype. No clear separation was found in the response of forest savory chemotypes to foliar selenium and silicon application. However, selenium-treated plants reduced proline accumulation under drought stress. Based on the obtained results, forest savory as a drought-resistance valuable medicinal plant can be introduced into the crop system, especially in regions with low precipitation and scarce water sources.
... In contrast, T. guianensis regained only 50% of its losses within 4 days, and it took until early-January (45 days) until the pre-drought stem diameter was regained, but already at the beginning of December the species showed a flattening of the stem increment curve (★). The rates of stem circumference shrinkage in relation to the dry time interval, the net circumference change between subsequent days and the standardized shrinkages ( Figures 5.1-3) highlighted that evergreen broadleaved and coniferous species are able to regulate stem water loss after a couple of sunny and dry days, probably by the closure of leaf stomata (Ying et al., 2015). If the duration of a dry spell exceeds four consecutive days, differences between families became apparent. ...
... Recovery from a drought can be interfered by xylem cavitation . Other drought stress effects that may negatively affect post-drought growth despite favorable growth conditions include damaged organelle structures, decreased photosynthetic activity or induced chlorophyll degradation (Ying et al., 2015). T. guianensis seems therefore to be Chapter 5 | Tree circumference changes and species-specific growth recovery after extreme dry events in a montane rainforest in southern Ecuador | 87 vulnerable to longer or higher frequency droughts. ...
The global climate change is affecting forests worldwide with effects regarding biodiversity and ecological services. Knowledge of tropical humid and dry forests are in this context of utmost importance. The main aim of the present thesis is the analysis of tree water relations and drought responses with a focus on adaptation strategies and plant functional types. The studies were conducted in two different locations, a seasonally dry tropical forest and an evergreen montane forest. Several hundred increment cores of trees were taken and high-resolution dendrometer measurements were recorded to analyze short and long term dynamics of circumference changes in connection with extreme climatic events. To support our analyses sap-flux data, volumetric soil water content, canopy coverage change and leaf phenology were also recorded. In the dry forest the tree species Ceiba trichistandra (leaf deciduous, stem succulent), Eriotheca ruizii (leaf deciduous, root succulent) and Erythrina velutina (leaf deciduous) were studied. C. trichistandra responded very sensitive to fluctuating moisture regimes with leaf phenology, sap flux and stem diameter variations, and can be regarded as a sensitive indicator for assessing climatic variations. In the montane rain forest, the focus was on dry intervals with a minimum of four consecutive days to examine how different tree species respond to drought stress. The averaged species-specific stem shrinkage rates and recovery times during and after dry periods were analyzed. The two deciduous broadleaved species Cedrela montana and Handroanthus chrysanthus showed the biggest stem shrinkage of up to 2 mm after 10 consecutive dry days. Moreover, great differences of recovery times after longer-lasting (i.e., eight to ten days) drought events between the two evergreen broadleaved species Vismia cavanillesiana and Tapirira guianensis were found. While V. cavanillesiana replenished to pre-drought stem circumference after only 5 days, T. guianensis needed 52 days on average to restore its circumference. Hence, a higher frequency of droughts might increase inter-species competition, species-specific mortality and therefore finally alter the species composition of the ecosystem. In light of the findings presented here regarding possible effects of climate change on different tree species, this dissertation serves as important contribution to enhance the understanding of tropical forest ecosystems.
... Declined LRWC in both Brassica cultivars (cv. PJN and VAR) during the PEG treatment indicated the loss of water content from the plant cells and faced osmotic disturbance, as reported by other studies [39,40]. However, LRWC was restored by the exogenous application of independent and combined NO and ABA under PEG which could be due to increased endogenous ABA or/and NO content, as evidenced by partially or fully improved LRWC in PJN and VAR, respectively. ...
... The difference in ABA and NO accumulation (less in VAR and more in PJN) as a result of PEG and PEGcombination treatments may point to the reason that tolerant genotypes react quicker to changes/maintain the endogenous ABA or/and NO levels, whilst it continued to increase in the sensitive genotypes, as suggested in time-course experiments in wheat and rice [46,47]. A predominant inhibition in total Chl content of both B. juncea cultivars indicates oxidative stress damage, similar to earlier reports in other plants such as cotton, maize etc [40,48]. The Chl loss was supposed to be due to the drought-induced changes in plant-water relations (i.e., LRWC), leading to a disruption in the chloroplast's biochemistry (such as photo-oxidation and chlorophyll degradation) [49]. ...
The present study was designed to see the effect of exogenous nitric oxide (NO) and abscisic acid (ABA) and their interaction on physiological and biochemical activities in leaves and roots of two Indian mustard (Brassica juncea) cultivars [cv. Pusa Jagannath (PJN) and Varuna (VAR)] exposed to polyethylene glycol (PEG)-induced drought stress. Seven days old hydroponically grown seedlings were treated with PEG (10%), sodium nitroprusside, a NO donor [NO (100 μM)] and abscisic acid [ABA (10 μM)], using different combinations as: Control, ABA, NO, PEG, PEG + ABA, PEG + NO, and PEG + NO + ABA. Results revealed that in response to PEG-induced drought stress leaf relative water content, chlorophyll, carotenoid and protein content decreased with increased production of O 2−● , MDA, H 2 O 2 , cysteine content and non-enzymatic antioxidants (including proline, flavonoid, phenolic, anthocyanin, and ascorbic acid), whereas, the enzymatic antioxidants (including SOD, CAT, APX, GR) showed the response range from no effect to increase or decrease in certain enzymes in both Brassica cultivars. The application of NO or/and ABA in PEG-stressed cultivars showed that both enzymatic and non-enzymatic antioxidants responded differently to attenuate oxidative stress in leaves and roots of both cultivars. Overall, PJN had the antioxidant protection mainly through the accumulation of non-enzymatic antioxidants, whereas VAR showed tolerance by the enhancement of both enzymatic and non-enzymatic antioxidant activities. Altogether, the study concluded that the independent NO and its interaction with ABA (PEG + NO and PEG + NO + ABA) were much effective than independent ABA (PEG + ABA) in lowering PEG-drought stress in Brassica cultivars.
... The rates of stem circumference shrinkage in relation to the dry time interval, the net circumference change between subsequent days and the standardized shrinkages (Figures 1-3) highlighted that evergreen broadleaved and coniferous species are able to regulate stem water loss after a couple of sunny and dry days, probably by the closure of leaf stomata (Ying et al., 2015). If the duration of a dry spell exceeds four consecutive days, differences between families became apparent. ...
... Recovery from a drought can be interfered by xylem cavitation (Luo et al., 2016). Other drought stress effects that may negatively affect post-drought growth despite favourable growth conditions include damaged organelle structures, decreased photosynthetic activity or induced chlorophyll degradation (Ying et al., 2015). T. guianensis seems therefore to be vulnerable to longer or higher frequency droughts. ...
Under drought conditions, even tropical rainforests might turn from carbon sinks to sources, and tree species composition might be altered by increased mortality. We monitored stem diameter variations of 40 tree individuals with stem diameters above 10 cm belonging to eleven different tree genera and three tree life forms with high-resolution dendrometers from July 2007 to November 2010 and additionally March 2015 to December 2017 in a tropical mountain rainforest in South Ecuador, a biodiversity hotspot with more than 300 different tree species belonging to different functional types. Although our study area receives around 2200 mm of annual rainfall, dry spells occur regularly during so-called “Veranillo del Niño” (VdN) periods in October-November. In climate change scenarios, droughts are expected with higher frequency and intensity as today. We selected dry intervals with a minimum of four consecutive days to examine how different tree species respond to drought stress, raising the question if some species are better adapted to a possible higher frequency and increasing duration of dry periods. We analyzed the averaged species-specific stem shrinkage rates and recovery times during and after dry periods. The two deciduous broadleaved species Cedrela montana and Handroanthus chrysanthus showed the biggest stem shrinkage of up to 2 mm after 10 consecutive dry days. A comparison of daily circumference changes over 600 consecutive days revealed different drought responses between the families concerning the percentage of days with stem shrinkage/increment, ranging from 27.5 to 72.5% for Graffenrieda emarginata to 45–55% for Podocarpus oleifolius under same climate conditions. Moreover, we found great difference of recovery times after longer-lasting (i.e., eight to ten days) VdN drought events between the two evergreen broadleaved species Vismia cavanillesiana and Tapirira guianensis. While Vismia replenished to pre-VdN stem circumference after only 5 days, Tapirira needed 52 days on average to restore its circumference. Hence, a higher frequency of droughts might increase inter-species competition and species-specific mortality and might finally alter the species composition of the ecosystem.
... Camptotheca acuminate is a perennial woody plant of the Nyssaceae family that is used for timber and camptothecin extraction (Yu et al. 2012;Ying et al. 2014). In addition, C. acuminate is native to China and adapted to the calcareous soil. ...
... During the growing season, plants usually exposed to variable water deficit. C. acuminate was described as drought tolerant by improving water retention, antioxidation, and membrane integrity (Ying et al. 2014). However, the research did not fully explain how this species adapted to calcareous soil with co-occurring water deficit and bicarbonate, which is very common under natural conditions (Deng et al. 2012;Hu et al. 2013). ...
Water deficit is one of the key factors that limits the carbon (C) assimilation and productivity of plants. The effect of variable water deficit on recently root-derived bicarbonate assimilation in Camptotheca acuminate seedlings was investigated. Three-month-old seedlings were subjected to three water regimes, well-watered (WW), moderate stress (MS), and severe stress (SS) induced by polyethyleneglycol, in conjunction with relatively high (H) and low (L) natural 13C-abundance of NaHCO3-labeled treatments in hydroponics for 14 days. The δ13C of the newly expanded leaves in H were generally more enriched in heavy isotopes than were those in L, indicative of the involvement of bicarbonate in aboveground tissues. The C isotope fractionation of newly expanded leaves relative to air (∆13Cair-leaves) ranged from 17.78 to 21.78‰ among the treatments. The ∆13Cair-leaves under the MS and SS treatments in H were both more negative than was that in L. A linear regression between Ci/Ca and ∆13Cair-leaves in both L and H were different from the theoretical regression. On the basis of the two end-member mixing model, the proportion of fixed CO2 supplied from bicarbonate contributing to the total photosynthetically inorganic C assimilation were 10.34, 20.05 and 16.60% under the WW, MS, and SS treatments, respectively. These results indicated that the increase in water deficit decreased the atmospheric CO2 gain but triggered a compensatory use of bicarbonate in C. acuminate seedlings.
... The majority of the maize lines assessed in the present study exhibited similar patterns in their physiological responses to drought stress and recovery. Consistent with the results reported in previous studies, drought induced decreases in leaf water content, water potential, osmotic potential, gas exchange parameters, chlorophyll content, Fv/Fm and nitrogen content, and increased H 2 O 2 accumulation and lipid peroxidation (Figures 2-6; Mahouachi et al., 2006;Efeoglu et al., 2009;Flexas et al., 2009;Posch and Bennett, 2009;Bibi et al., 2010;Vassileva et al., 2011;Jiang et al., 2012;Ebrahimiyan et al., 2013;Li-Marchetti et al., 2015;Ying et al., 2015). After recovery, most of these physiological parameters rapidly returned to normal levels (Figures 2-6; Wang and Huang, 2004;Efeoglu et al., 2009;Flexas et al., 2009;Chai et al., 2010;Puangbut et al., 2010;Vassileva et al., 2011;Jiang et al., 2012;Domenghini et al., 2013). ...
... Chlorophyll, a photosynthetic pigment, is involved in light absorption and plays an important role in plant photosynthesis. As drought stress can accelerate chlorophyll decomposition, chlorophyll content is one of the most frequently used metrics for the severity of drought stress (Efeoglu et al., 2009;Ying et al., 2015). As expected, we found that the chlorophyll content in all lines significantly decreased under drought stress ( Figure 4C). ...
Non-irrigatedcropsintemperateclimatesandirrigatedcropsinaridclimatesaresubjectedtocontinuouscyclesofwaterstressandre-watering.Thus,fastandefficientrecoveryfromwaterstressmaybeamongthekeydeterminantsofplantdroughtadaptation.Thepresentstudywasdesignedtocomparativelyanalyzetherolesofdroughtresistanceanddroughtrecoveryindroughtadaptationandtoinvestigatethephysiologicalbasisofgenotypicvariationindroughtadaptationinmaize(Zeamays)seedlings.Astheseedlingsbehavioringrowthassociatewithyieldunderdrought,itcouldpartlyreflectthepotentialofdroughtadaptability.Growthandphysiologicalresponsestoprogressivedroughtstressandrecoverywereobservedinseedlingsof10maizelines.Theresultsshowedthatdroughtadaptabilityiscloselyrelatedtodroughtrecovery(r=0.714∗∗),butnottodroughtresistance(r=0.332).Droughtinduceddecreasesinleafwatercontent,waterpotential,osmoticpotential,gasexchangeparameters,chlorophyllcontent,Fv/Fmandnitrogencontent,andincreasedH2O2accumulationandlipidperoxidation.Afterrecovery,mostofthesephysiologicalparametersrapidlyreturnedtonormallevels.Thephysiologicalresponsesvariedbetweenlines.Furthercorrelationanalysisindicatedthatthephysiologicalbasesofdroughtresistanceanddroughtrecoveryaredefinitelydifferent,andthatmaintaininghigherchlorophyllcontent(r=0.874∗∗∗)andFv/Fm(r=0.626∗)underdroughtstresscontributestodroughtrecovery.Ourresultssuggestthatbothdroughtresistanceandrecoveryarekeydeterminantsofplantdroughtadaptation,andthatdroughtrecoverymayplayamoreimportantrolethanpreviouslythought.Inaddition,leafwaterpotential,chlorophyllcontentandFv/Fmcouldbeusedasefficientreferenceindicatorsintheselectionofdrought-adaptivegenotypes.
... Phenotypically, the leaves of the foxtail millet accessions showed to be yellowish (starting from the basal of the plants) following the drought conditions periods drought stress (Figure 2). RWC is a measure of water status in plants as a physiological consequence of groundwater content (Ying et al. 2015). RWC is related to the ability to absorb water from the soil and the ability of plants to control water loss through stomata (Parkash and Singh 2020). ...
Nisa C, Jadid N. 2021. Exogenous acetic acid pre-treatment increases drought tolerance of two Indonesian foxtail millet (Setaria italica) accessions. Biodiversitas 22: 2117-2124. Drought is one of the external factors that affect the productivity of food crops. Some biotechnological approaches had been developed to increase plant resistance to drought stress. Moreover, an adjustment in plant cultivation system is also reported as alternative way to enhance plant resistance to water deficit conditions, especially during their initial vegetative phase. This study aimed to determine the effect of exogenous acetic acid pre-treatment on some Indonesian foxtail millet (Setaria italica) accessions under drought stress conditions. Two different foxtail millet accessions were used in this study: Gambir Manis and Polman Kuning. Morphological and physiological parameters were observed during this study, including plant height, number of leaves, root length, relative water content, total chlorophyll and carotenoid content, and panicle weight. Our results showed that all foxtail millet accessions survived drought stress condition after being pre-treated with exogenous acetic acid. Yet, some morphological parameters were significantly affected. Meanwhile, physiological parameters were not significantly affected. Overall, our data suggest that exogenous acetic acid pre-treatment could enhance drought avoidance in S. italica accessions. This might be due to acetic acid-induced jasmonic acid modulation and secondary metabolites production in S. italica during water deficit exposure.
... Upland rice (Paddy Gogo) is a rice plant that can grow well on marginal lands without having to use super luxurious technology. Plants that are tolerant and sensitive to drought stress will show different physiological responses (Ying et al., 2015;dos Santos et al., 2022). Drought-resistant plants can be seen from the nature of their roots or through root penetration tests and seed germination (Pandey & Shukla 2015;Taylor et al., 2021). ...
The aim of this study was to determine the drought tolerance limit of five upland rice (Paddy Gogo) cultivars in the germination phase. This research was carried out at the Seed Science and Technology Laboratory, Faculty of Agriculture, University of Tadulako, Palu, Indonesia, from September to October 2020. This study was arranged using a completely randomized design (CRD) with a factorial design of 2 factors. The first factor was the cultivar consisting of five cultivars, i.e., Pau Tau Leru, Jahara, Uva Buya, Buncaili, and Kalendeng. The second factor was the Polyethylene Glycol (PEG) concentration which consisted of five levels, i.e., Without PEG, 10%, 20%, 30% and 40% PEG. There were 25 treatment combinations. Each treatment was repeated three times (75 experimental units). The results showed that Uva Buya and Jahara cultivars had a high tolerance for PEG which was characterized by the maximum growth potential, germination power above 85%, and germination time in less than 4 days with the treatment of 40% PEG concentration. Meanwhile, Pau Tau Leru, Buncaili, and Kalendeng cultivars were able to grow and germinate well up to 10% PEG concentration. Both Uva Buya and Jahara cultivars also had a longer and heavier plumule and radicle, and larger roots.
... Meanwhile, under high soil pH stress, the VcSOD1, VcSOD2 and VcSOD3 gene expression levels in blueberry decreased, and the VcCAT1, VcCAT2 and VcCAT3 expression levels increased (Figure 7), which may be the main reason for the observed change in enzyme activity (Dionisio-Sese & Tobita, 1998). In addition, abiotic stress inhibits chlorophyll synthesis and reduces plant photosynthetic intensity, and damage to the plant photosynthetic system is related to osmotic adjustment substances and antioxidant enzyme systems (Efeoglu et al., 2009;Yousfi et al., 2010;Ying et al., 2015;Zhang et al., 2021). In the present study, the SPAD of blueberry leaves decreased significantly under the high soil pH stress treatment, and photosynthetic indices, such as P n , E, and G s , also significantly decreased. ...
High soil pH is one of the main abiotic factors that negatively affects blueberry growth and cultivation. However, no comprehensive evaluation of the high soil pH tolerance of different blueberry cultivars has been conducted. Herein, 16 phenotypic and physiological indices of 15 blueberry cultivars were measured through pot experiments, and the high-pH soil tolerance coefficient (HSTC) was calculated based on these indices to comprehensively evaluate the high-soil-pH tolerance of plants. The results demonstrated that high soil pH stress inhibited blueberry 77.growth, and MDA, soluble sugar (SS), and soluble protein (SP) levels increased in leaves. Moreover, in all cultivars, CAT activity in the antioxidant system was enhanced, whereas SOD activity was reduced, and the relative expression levels of the antioxidant enzyme genes SOD and CAT showed similar changes. In addition, the leaf chlorophyll relative content (SPAD), net photosynthetic rate (Pn), transpiration rate (E), and stomatal conductance (Gs) decreased, while changes in the intercellular CO2 concentration (Ci) were noted in different cultivars. Finally, according to the comprehensive evaluation value D obtained from the combination of principal component analysis (PCA) and membership function (MF), the 15 blueberry cultivars can be divided into 4 categories: high soil pH-tolerant type [‘Briteblue’ (highest D value 0.815)], intermediate tolerance type (‘Zhaixuan 9’, ‘Zhaixuan 7’, ‘Emerald’, ‘Primadonna’, ‘Powderblue’ and ‘Chandler’), low high soil pH-tolerant type (‘Brightwell’, ‘Gardenblue’, ‘Plolific’ and ‘Sharpblue’) and high soil pH-sensitive type [‘Legacy’, ‘Bluegold’, ‘Baldwin’ and ‘Anna’ (lowest D value 0.166)]. Stepwise linear regression analysis revealed that plant height, SS, E, leaf length, Ci, SOD, and SPAD could be used to predict and evaluate the high soil pH tolerance of blueberry cultivars.
... Drought stress is one of the abiotic factors that influence crops' physiological metabolism, growth, and yield. Some researchers reported that drought stressinduced stomatal closure, reduced transpiration, increased oxidative stress, interfered with photosynthesis, and changed chlorophyll contents (Ying et al. 2015;Liu et al. 2017;Nemeskéri and Helyes 2019;Almuwayhi 2021). The morphology changes of curly pepper also occurred during drought stress, such as reduced plant growth, flower abortion, declined biomass, and yield (Mardani et al. 2017;Rosmaina et al. 2018;Widuri et al. 2020). ...
Rosmaina, Ridho A, Zulfahmi. 2022. Response of morpho-physiological traits to drought stress and screening of curly pepper (Capsicum annuum) genotypes for drought tolerance. Biodiversitas 23: 5469-5480. Developing drought-tolerant genotypes are required to face drought condition that often occurs. The study aimed was to assess the growth, biomass, yield traits, and gas exchange of fifteen curly pepper (Capsicum annuum L.) genotypes under normal and drought-stress conditions and to determine the key traits as indicators for selecting and identifying the drought-tolerant curly pepper genotypes. Fifteen curly pepper genotypes were cultivated under normal and drought-stress conditions. Twenty-one morphological and physiological traits were recorded in the reproductive phase. The data obtained were subjected to analysis of variance, Principal Component Analysis (PCA), and UPGMA dendrogram cluster analysis. This study showed that drought stress conditions significantly reduced plant growth, biomass, yield characters, photosynthesis rate, stomatal conductance, transpiration rate, and mesophyll conductance compared to normal conditions. Based on PCA analysis, stomatal limitation, mesophyll and stomatal conductances, root length, photosynthesis rate, fruit weight per plant, chlorophyll b, number of fruit, and transpiration rate were established as indicators for screening drought tolerant genotypes. The UIN-70 and UIN-65 were highly drought-tolerant genotypes according to the MFVD index. UPGMA dendrogram displayed clustering of the curly pepper genotypes consistent with the genotype's cluster based on the MFVD index. This study's findings can be utilized to improve curly pepper's drought tolerance in the future.
... The impact of rainfall on WUE is complex, and there are differences in WUE among various plant species (Xiao et al., 2013). Some studies have shown that WUE increases with water deficit (Ying et al., 2015) and decreases with increasing precipitation (Niu et al., 2011;Huang et al., 2017). Moreover, the WUE has been used to describe the coupling relationship between vegetation productivity and carbon supply and water consumption, which is an important part of the coupling cycles of carbon-nitrogen-water (Felzer et al., 2011;Yu et al., 2014). ...
Nitrogen (N) deposition tends to accompany precipitation in temperate forests, and vegetation productivity is mostly controlled by water and N availability. Many studies showed that tree species response to precipitation or N deposition alone influences, while the N deposition and precipitation interactive effects on the traits of tree physiology, especially in non-structural carbohydrates (NSCs) and long-term water use efficiency (WUE), are still unclear. In this study, we measured carbon stable isotope (δ13C), total soluble sugar and starch content, total phenols, and other physiological traits (e.g., leaf C:N:P stoichiometry, lignin, and cellulose content) of two dominant tree species (Quercus variabilis Blume and Liquidambar formosana Hance) under canopy-simulated N deposition and precipitation addition to analyze the changes of long-term WUE and NSC contents and to explain the response strategies of dominant trees to abiotic environmental changes. This study showed that N deposition decreased the root NSC concentrations of L. formosana and the leaf lignin content of Q. variabilis. The increased precipitation showed a negative effect on specific leaf area (SLA) and a positive effect on leaf WUE of Q. variabilis, while it increased the leaf C and N content and decreased the leaf cellulose content of L. formosana. The nitrogen–water interaction reduced the leaf lignin and total phenol content of Q. variabilis and decreased the leaf total phenol content of L. formosana, but it increased the leaf C and N content of L. formosana. Moreover, the response of L. formosana to the nitrogen–water interaction was greater than that of Q. variabilis, highlighting the differences between the two dominant tree species. The results showed that N deposition and precipitation obviously affected the tree growth strategies by affecting the NSC contents and long-term WUE. Canopy-simulated N deposition and precipitation provide a new insight into the effect of the nitrogen–water interaction on tree growth traits in a temperate forest ecosystem, enabling a better prediction of the response of dominant tree species to global change.
... RWC has been used as one of the important indicators of cell and tissue hydration state [45]. Increased RWC is important to support plant growth under stresses. ...
Mesembryanthemum crystallinum (common ice plant) is one of the facultative halophyte plants, and it serves as a model for investigating the molecular mechanisms underlying its salt stress response and tolerance. Here we cloned one of the homeobox transcription factor (TF) genes, McHB7, from the ice plant, which has 60% similarity with the Arabidopsis AtHB7. Overexpression of the McHB7 in Arabidopsis (OE) showed that the plants had significantly elevated relative water content (RWC), chlorophyll content, superoxide dismutase (SOD), and peroxidase (POD) activities after salt stress treatment. Our proteomic analysis identified 145 proteins to be significantly changed in abundance, and 66 were exclusively increased in the OE plants compared to the wild type (WT). After salt treatment, 979 and 959 metabolites were significantly increased and decreased, respectively, in the OE plants compared to the WT. The results demonstrate that the McHB7 can improve photosynthesis, increase the leaf chlorophyll content, and affect the TCA cycle by regulating metabolites (e.g., pyruvate) and proteins (e.g., citrate synthase). Moreover, McHB7 modulates the expression of stress-related proteins (e.g., superoxide dismutase, dehydroascorbate reductase, and pyrroline-5-carboxylate synthase B) to scavenge reactive oxygen species and enhance plant salt tolerance.
... This has been explained by studies in that when plants are stressed by drought, the biomass is distributed more underground in order to absorb more water and nutrients, while minimizing water loss due to transpiration [28]. It also can be concluded from the studies of Ying, Narayan Bhusal, and Lei et al. that drought stress had distinct impacts on the morphological growth of various tree species, as well as on different variations or provenances of the same tree species [29][30][31]. In this study, the seedling height growth, ground diameter growth, and the aboveground biomass of different provenances declined as the stress levels increased, which was consistent with the above results. ...
Melia azedarach Linn. is a deciduous tree of the Melia genus in the Meliaceae family that is native to China. To study the mechanism of drought resistance in Melia azedarach and evaluate the drought resistance capacity of each provenance, we selected eight provenances (Shandong Kenli, Jiangsu Pizhou, Hubei Shayang, Jiangsu Xuanwu, Jiangxi Xihu, Jiangsu Jurong, Guangdong Luogang, and Henan Shihe) as the research subjects and set four levels of drought stress treatment (CK: 75% of field capacity, mild drought: 60% of field capacity, moderate drought: 45% of field capacity, and severe drought: 30% of field capacity). The results showed that the growth in the seedling height and the ground diameter, the leaf relative water content, transpiration rate (Tr), net photosynthetic rate (Pn), stomatal conductance (Gs), and the content of chlorophyll (Chl) decreased with the increasing stress levels, while the root–shoot ratio, water saturation deficit, and the contents of malondialdehyde (MDA) increased. The SOD in most provenances initially increased and then decreased, reaching a peak during moderate drought. At the late stage of treatment, the magnitude of the changes in the photosynthetic indicators was more pronounced than in the physiological indicators. Principal component analysis showed that the contribution of all four principal components under the three drought stresses was above 85%, which represented the majority of the original data. Combined with the affiliation function method and weights, the comprehensive evaluation value (D value) of the drought resistance was calculated for the eight provenances. Then, we obtained the order of drought resistance of the test materials under the three drought stresses, respectively. The combined results revealed that the drought resistance of Henan Shihe and Jiangxi Xihu was stronger, while the drought resistance of Guangdong Luogang and Hubei Shayang was weaker. Based on the above findings, we can select provenances with strong and weak drought resistance for transcriptome sequencing to screen drought-resistant genes for an in-depth study at the molecular level.
... Furthermore, they discovered that applying glycine betaine to drought-stressed plants induced substantial APX activity. Thus, in Carapa guianensis, glycine betaine reduced lipid peroxidation in drought-stressed plants by positively modulating APX activity 53 . ABA increased antioxidant enzymes APX and induced apoplastic H2O2 accumulation in maize leaves 17 . ...
Drought stress is a significant limitation to the production and yield of black gram [Vigna mungo (L.) Hepper] and abscisic acid plays a subtle role in the biosynthetic pathway during drought stress. The present study examined the morphology, biochemical, relative water content and antioxidant activities of black gram plants treated with various abscisic acid (ABA) levels under drought conditions. The ABA at 50 ppm concentration showed promising recovery of morphological characters compared to other concentrations. The photosynthetic pigments, biochemical constituents, malondialdehyde and antioxidant enzymes (CAT, POD, SOD and APX) were active at 50 ppm. Infrared Spectroscopic (IR) analysis of black gram leaves in a bandwidth ranging from 400 to 4000 cm-1 revealed a change in metabolites under drought stress and exogenous ABA application. The FTIR spectroscopy results warrant that the expression of functional organic compounds in the drought response of black gram can aid in the discovery of new drought-tolerant traits. As a result, ABA-responsive cultivars can cultivate and produce drought-resistant black gram varieties in arid and semi-arid climates.
... In the present study, under drought treatment, MDA content and EC were significantly lower than those in the wild type (Figures 6E,F). Therefore, the results suggested there was less production of ROS in response to water deficit in overexpression lines, which helped to maintain membrane integrity (Ying et al., 2015). The results of this study and others suggest that overexpression of GmAP2/ERF144 contributes to improved drought stress tolerance by increasing water retention capability. ...
Drought is a major environmental constraint that causes substantial reductions in plant growth and yield. Expression of stress-related genes is largely regulated by transcription factors (TFs), including in soybean [Glycine max (L.) Merr.]. In this study, 301 GmAP2/ERF genes that encode TFs were identified in the soybean genome. The TFs were divided into five categories according to their homology. Results of previous studies were then used to select the target gene GmAP2/ERF144 from among those up-regulated by drought and salt stress in the transcriptome. According to respective tissue expression analysis and subcellular determination, the gene was highly expressed in leaves and encoded a nuclear-localized protein. To validate the function of GmAP2/ERF144, the gene was overexpressed in soybean using Agrobacterium-mediated transformation. Compared with wild-type soybean, drought resistance of overexpression lines increased significantly. Under drought treatment, leaf relative water content was significantly higher in overexpressed lines than in the wild-type genotype, whereas malondialdehyde content and electrical conductivity were significantly lower than those in the wild type. Thus, drought resistance of transgenic soybean increased with overexpression of GmAP2/ERF144. To understand overall function of the gene, network analysis was used to predict the genes that interacted with GmAP2/ERF144. Reverse-transcription quantitative PCR showed that expression of those interacting genes in two transgenic lines was 3 to 30 times higher than that in the wild type. Therefore, GmAP2/ERF144 likely interacted with those genes; however, that conclusion needs to be verified in further specific experiments.
... Ying et al., [110] Cowpea Increased vegetative and flowering and caused reduced shoot dry weight. Ndiso et al., [111] Faba bean Elevated levels of proline, soluble sugars and protein content in the leaves of Faba bean. ...
Water scarcity is known as a major stumbling block towards crop development and its output all over the world. Certain free-living bacterial strains have been found near the plant root zones which have shown to improve resistance of plants towards water stress. Despite availability of basic nutrients, drought an abiotic factor substantially inhibits growth, development and yield of crops by causing an increase in ethylene levels. It is a good idea to incorporate the use of a management tool which is the utilization of plant growth-promoting rhizobacteria to help several crops manage drought conditions. Drought stress in crops can be alleviated by reducing ethylene synthesis, exopolysaccharide, osmoregulation, Indole-3-acetic acid and aggregation with the ACC deaminase-containing plant growth-promoting rhizobacteria. Inoculating pathogens like root rot (Macrophomina phaseolina) affected plant with Pseudomonas fluorescens strain TDK1 with ACC deaminase function improves drought stress. Using plant growth-promoting rhizobacteria to mitigate the negative imbibes of drought in most crops is a good idea. Several studies have been carried out on plant growth-promoting rhizobacteria, as its inoculation not only manages drought related Review Article Kumar et al.; IJPSS, 33(21): 44-66, 2021; Article no.IJPSS.68994 45 conditions but increases root hair growth and lateral root, which assist in increased water and nutrient uptake. It limits ethylene supply, alternatively increases plant root growth by hydrolyzing 1-aminocyclopropane-1-carboxylic acid (ACC). This review will give us a perspective on the importance of plant growth-promoting rhizobacteria, as it is one of the efficient tools that helps manage drought stress on several crops.
... Since Rab11 proteins are known to be key players in membrane recycling (O'sullivan and Lindsay, 2020), we assumed that during water stress, which leads to membrane damage (Ying et al., 2015;Abid et al., 2018), the activity of RabA2b promoter would be observed throughout the plant in most of its cell types. Therefore, it was surprising to find that during osmotic stress, the ProRabA2b-GUS signal was restricted mainly to the vasculature, in both the shoot and the root (Figure 2). ...
Rab proteins are small GTPases that are important in the regulation of vesicle trafficking. Through data mining, we identified RabA2b to be stress responsive, though little is known about the involvement of RabA in plant responses to abiotic stresses. Analysis of the RabA2b native promoter showed strong activity during osmotic stress, which required the stress hormone Abscisic acid (ABA) and was restricted to the vasculature. Sequence analysis of the promoter region identified predicted binding motifs for several ABA-responsive transcription factors. We cloned RabA2b and overexpressed it in Arabidopsis. The resulting transgenic plants were strikingly drought resistant. The reduced water loss observed in detached leaves of the transgenic plants could not be explained by stomatal aperture or density, which was similar in all the genotypes. Subcellular localization studies detected strong colocalization between RabA2b and the plasma membrane (PM) marker PIP2. Further studies of the PM showed, for the first time, a distinguished alteration in the PM proteome as a result of RabA2b overexpression. Proteomic analysis of isolated PM fractions showed enrichment of stress-coping proteins as well as cell wall/cuticle modifiers in the transgenic lines. Finally, the cuticle permeability of transgenic leaves was significantly reduced compared to the wild type, suggesting that it plays a role in its drought resistant properties. Overall, these data provide new insights into the roles and modes of action of RabA2b during water stresses, and indicate that increased RabA2b mediated PM trafficking can affect the PM proteome and increase drought tolerance.
... After centrifugation at 10,000× g for 10 min, the absorbance (A) of the 10-fold diluted supernatants was measured at 532 nm and values corresponding to non-specific absorption at 450 nm and a correction factor for non-specific turbidity at 600 nm. MDA concentration determined on a fresh weight basis was calculated as described elsewhere [36] with the following Formula (1): ...
Photosynthetic pigments of plants capture light as a source of energy for photosynthesis. However, the amount of energy absorbed often exceeds its utilization, thus causing damage to the photosynthetic apparatus. Plants possess several mechanisms to minimize such risks, including non-photochemical quenching (NPQ), which allows them to dissipate excess excitation energy in the form of harmless heat. However, under non-stressful conditions in indoor farming, it would be favorable to restrict the NPQ activity and increase plant photosynthetic performance by optimizing the light spectrum. Towards this goal, we investigated the dynamics of NPQ, photosynthetic properties, and antioxidant activity in the leaves of tomato plants grown under different light qualities: monochromatic red (R), green (G), or blue (B) light (L) at 80 µmol m−2 s−1 and R:G:B = 1:1:1 (referred to as the white light (WL)) at 120 µmol m−2 s−1. The results confirm that monochromatic BL increased the quantum efficiency of PSII and photosynthetic pigments accumulation. The RL and BL treatments enhanced the NPQ amplitude and showed negative effects on antioxidant enzyme activity. In contrast, plants grown solely under GL or WL presented a lower amplitude of NPQ due to the reduced accumulation of NPQ-related proteins, photosystem II (PSII) subunit S (PsbS), PROTON GRADIENT REGULATION-LIKE1 (PGRL1), cytochrome b6f subunit f (cytf) and violaxanthin de-epoxidase (VDE). Additionally, we noticed that plants grown under GL or RL presented an increased rate of lipid peroxidation. Overall, our results indicate the potential role of GL in lowering the NPQ amplitude, while the role of BL in the RGB spectrum is to ensure photosynthetic performance and photoprotective properties.
... Osmotic adjustment is considered an important part of drought resistance (such as MDA and proline content; Wei et al., 2009;Fang and Xiong, 2015;Chen et al., 2016), and there is a positive correlation with the indicators of photosynthesis (Hura et al., 2007). At the same time, drought stress will cause the decomposition of Chl, which in turn affects crop photosynthesis (Efeoglu et al., 2009;Ying et al., 2015). Therefore, it is necessary to combine multiple traits such as morphology, physiology, biochemical and yield traits when conducting drought resistance evaluation and analysis. ...
Drought is one of the main abiotic stresses that seriously influences cotton production. Many indicators can be used to evaluate cotton drought tolerance, but the key indicators remain to be determined. The objective of this study was to identify effective cotton drought tolerance indicators from 19 indices, including morphology, photosynthesis, physiology, and yield-related indices, and to evaluate the yield potential of 104 cotton varieties under both normal and drought-stress field conditions. Combined with principal component analysis (PCA) and a regression analysis method, the results showed that the top five PCs among the 19, with eigenvalues > 1, contributed 65.52, 63.59, and 65.90% of the total variability during 2016 to 2018, respectively, which included plant height (PH), effective fruit branch number (EFBN), single boll weight (SBW), transpiration rate (Tr) and chlorophyll (Chl). Therefore, the indicator dimension decreased from 19 to 5. A comparison of the 19 indicators with the 5 identified indicators through PCA and a combined regression analysis found that the results of the final cluster of drought tolerance on 104 cotton varieties were basically consistent. The results indicated that these five traits could be used in combination to screen cotton varieties or lines for drought tolerance in cotton breeding programs, and Zhong R2016 and Xin lu zao 45 exhibited high drought tolerance and can be selected as superior parents for good yield performance under drought stress.
... The work of [17] on two provenances of Camptotheca acuminata showed that the provenance with higher drought tolerance had better water retention capacity, antioxidant enzyme activity and membrane integrity. ...
The adaptation of Anacardium occidentale L. to water deficit conditions has become essential in the context of climate change in Casamance, Senegal. Water deficit is one of the main causes that strongly affect the productivity of woody species. Thus, the promotion of tolerant varieties that can withstand the uncertainty of rainfall and its deficits is a solution to adapt to the effects of climate change. The study of the tolerance of four provenances of Anacardium occidentale L under drought stress conditions (12.5%, 25%, 50% and 100% of field capacity) was carried out in a semi-controlled environment. The measurement of height, total dry biomass, collar diameter and root length and relative water content, allowed us to obtain the results on the growth and physiological reactions of Anacardium occidentale provenances under water stress. At a high level of drought stress (12.5%), the best growth was obtained with plants from the Ziguinchor provenance, which had higher survival rates, heights, collar diameters and relative water content than the Kolda, Sédhiou and Goudomp provenances. These results show that the Ziguinchor plants provenance is more tolerant to water stress than the other provenances tested. This study recommends the use of the Ziguinchor Anacardium occcidentale provenance to fight against the effects of climate change in Casamance (Senegal).
... They kept their leaflets more open under severe drought, with lower assimilation costs, showed low photoinhibition and also had the highest overall water-use efficiency (Figures 3 and 4). These results are in accordance with other studies, where tree provenances from more xeric locations showed a higher physiological ability to cope with drought (Nguyen-Queyrens and Bouchet-Lannat 2003, López et al. 2009, Corcuera et al. 2012, Ying et al. 2015, Matías et al. 2019. ...
Photoprotection is a plant functional mechanisms to prevent photooxidative damage by excess light. This is most important when carbon assimilation is limited by drought, and as such, it entails a trade-off between carbon assimilation vs stress avoidance. The ecological adaptation of plants to local water availability can lead to different photoprotective strategies. To test this, we used different provenances of Caesalpinia spinosa (Mol.) Kuntze (commonly known as “tara”) along a precipitation gradient. Tara is a Neotropical legume tree with high ecological and commercial value, found in dry tropical forests, which are increasingly threatened by climate change. Morphological and physiological responses of tara provenances were analyzed under three different treatments of drought and leaflet immobilization i.e., light stress, in a common garden greenhouse experiment.
Tara quickly responded to drought by reducing stomatal conductance, evapotranspiration, photochemical efficiency, carbon assimilation and growth, while increasing structural and chemical photoprotection (leaflet angle and pigments for thermal dissipation). Leaflet closure was an efficient photoprotection strategy with overall physiological benefits for seedlings as it diminished the evaporative demand and avoided photodamage, but also entailed costs by reducing net carbon assimilation opportunities. These responses depended on seed origin, with seedlings from the most xeric locations showing the highest dehydration tolerance, suggesting local adaptation and highlighting the value of different strategies under distinct environments. This plasticity on its response to environmental stress allows tara to thrive in locations with contrasting water availability.
Our findings increase the understanding of the factors controlling the functional ecology of tara in response to drought, which can be leveraged to improve forecasts of changes in its distribution range, and for planning restoration projects with this keystone tree species.
... After centrifugation at 10,000 × g for 10 min, the absorbance (A) of the 10-fold diluted supernatants was measured at 532 nm and values corresponding to non-specific absorption at 450 nm and a correction factor for non-specific turbidity at 600 nm. The MDA concentration determined on a fresh weight basis was calculated according to Ying et al. (2015) with the following formula: ...
The objective of this study was to identify the effect of abscisic acid (ABA), putrescine (Put) and hydrogen peroxide (H2O2) foliar pre-treatment on drought tolerance of barley. Despite water limitation, ABA-sprayed plants preserved increased water content, photosynthetic efficiency of PSII (ΦPSII) and CO2 assimilation rate (Pn) compared to untreated stressed plants. The ABA-treated plants presented also the lowest rate of lipid peroxidation (MDA), lowered the rate of PSII primary acceptor reduction (1-qP) and increased the yield of regulated energy dissipation (NPQ) with higher accumulation of PGRL1 (PROTON GRADIENT REGULATION LIKE1) protein. These plants preserved a similar level of photochemical efficiency and the rate of electron transport of PSII (ETR II) to the well-watered samples. The significantly less pronounced response was observed in Put-sprayed samples under drought. Additionally, the combined effects of drought and H 2 O 2 application increased the 1-qP and quantum yield of non-regulated energy dissipation in PSII (ΦNO) and reduced the accumulation of Rubisco activase (RCA). In conclusion, ABA foliar application allowed to balance water retention and preserve antioxidant capacity resulting in efficient photo-synthesis and the restricted risk of oxidative damage under drought. Neither hydrogen peroxide nor putrescine has been able to ameliorate drought stress as effectively as ABA.
... Chlorophyll content is one of the most commonly used parameters to measure the severity of drought stress (Ying, 2015) as drought stress is thought to damage photosynthetic apparatus and diminish chlorophyll content (Fu & Huang, 2001 As such, the decreasing trend of chlorophyll a in D. oliveri implies correspondence to drought avoidance as may be expected with an isohydric behavior. On the contrary, some studies have suggested that chlorophyll content is positively associated with drought tolerance and recovery (Chen, 2016) and that the potential photo-oxidative damage can be remediated by increasing levels of carotenoids, which play a central role in the assembly of the light-harvesting complex in the photosystem, regulate photomorphogenesis, and provide photoprotection (Munné-Bosch & Alegre, 2000). ...
Dalbergia cochinchinensis and D. oliveri are classified as vulnerable and endangered, respectively, in the IUCN Red List and under continued threat from deforestation and illegal harvesting for rosewood. Despite emerging efforts to conserve and restore these species, little is known of their responses to drought and heat stress, which are expected to increase in the Greater Mekong Subregion where the species co-occur and are endemic. In this study of isolated and combined drought and heat effects, we found that D. oliveri had an earlier stomatal closure and more constant midday water potential in response to increasing drought level, suggesting that D. oliveri is relatively isohydric while D. cochinchinensis is relatively anisohydric. Heat shock and drought had synergistic effects on stomatal closure. Our results indicate contrasting relationships in water relations, photosynthetic pigment levels, and total soluble sugars. An increase in chlorophyll a was observed in D. cochinchinensis during drought, and a concomitant increase in carotenoid content likely afforded protection against photo-oxidation. These physiological changes correlated with higher total soluble sugars in D. cochinchinensis. By contrast, D. oliveri avoided drought by reducing chlorophyll content and compromising productivity. Anisohydry and drought tolerance in D. cochinchinensis are adaptations which fit well with its ecological niche as a pioneering species with faster growth in young trees. We believe this understanding of the stress responses of both species will be crucial to their effective regeneration and conservation in degraded habitats and in the face of climate change.
... One of the first responses of plants to drought is the decrease in RWC (Ying et al. 2015). Although the substrate showed a significant reduction in water potential after the 4th day, A. strobilacea plants showed this response only on day 8 of water restriction, which showcases the ability of these plants to prevent water loss for a certain period despite the highly dehydrated soil. ...
Global warming reduces water availability, exposing plants to more pronounced wet/dry cycles during their lifetime. Under these circumstances, epiphytic bromeliads can be more responsive due to their lack of contact with soil and high dependence on atmospheric water, especially in the case of juvenile individuals, which lose water more intensely than conspecific adults. In this study, we hypothesized that juvenile plants of Acanthostachys strobilacea (Schult. & Schult.f.) Klotzsch would exhibit rapid metabolic defense mechanisms to tolerate the leaf water loss caused by short-term water withholding (i.e. mild to moderate stress). We exposed plants to an 8-day water restriction and assessed their enzymatic antioxidant capacity and carbohydrate content. At 4 days of water restriction, A. strobilacea plants showed starch mobilization and increased the soluble carbohydrate content. After 8 days, carbohydrate reserves were depleted and the antioxidant enzyme activity was stimulated. Our results demonstrated that juvenile epiphytic bromeliads exhibit rapid metabolic adjustments to short-term water deficiency, which might be crucial for their survival in the face of the expected intensification of drought.
... In our study, BBI-expressing plants displayed more tolerance to drought stress when compared to the WT, which showed wilting symptoms at 9 days of water withdrawal while transgenic lines possessed more turgid leaves as a result of the higher RWC observed. Many studies have shown and confirmed that RWC can be used as an indicator for drought tolerance as it signifies the degree of tissue hydration and the ability of plants to retain water use under stressful conditions, which result in the maintenance of physiological functioning and growth processes (Ying et al., 2015). The observed tolerance might be associated with the slight decrease in RWC experienced by transgenic plants while the wild-type maintained lower RWC. ...
Serine protease inhibitors (SPIs) play an important role in cell survival, development and host defense. In plants, serine protease inhibitors such as the Kunitz-type inhibitor (KTI) and the Bowman-Birk inhibitor (BBI) have been shown to be induced in response to abiotic stress such as salinity and drought resulting in tolerance to these stresses. In this study, Arabidopsis thaliana (T3) plants overexpressing the BBI gene from maize were generated and subjected to drought stress in order to study the role of BBI protease inhibitor in drought tolerance. Drought treatment of four-week-old Arabidopsis plants was performed by withholding water from plants for nine days and harvested plant material was used for physiological and biochemical analysis. The transgenic lines exhibited normal growth after nine days of drought as compared to the wild-type. The results also showed a higher leaf relative water content (RWC) in transgenic lines when compared to the wild-type (WT), with line 2 having the highest RWC of 72% and the WT having the lowest RWC of 32%. Trypsin-inhibitor activity indicated that the total protein of the positive transgenic plants had stronger protease inhibitory activity than the wild-type. Transgenic lines overexpressing BBI also showed reduced lipid peroxidation (MDA content) as well as enhanced activity of antioxidants glutathione-s-transferase (GST) and ascorbate peroxidase (APX). These results suggest that BBI protease inhibitor leads to drought tolerance associated with reduction in drought-induced oxidative stress.
... Chlorophyll a and carotenoid in leaf were extracted using 96 vol% ethanol and measured by spectrophotometer (UV-2602, USA) at 470 nm, 648 nm, 664 nm (Ying et al., 2015). The chlorophyll and carotenoid content were calculated according to the formula of Lichtenthaler (1987). ...
Tomato is one of the popular vegetables in the world. However, drought has become more serious in recent years. Drought strongly reduced the development and yield of tomato. Thus, the effect of drought stress condition (½ Murashige and Skoog's medium supplemented with 35 g.L-1 mannitol) and thermal pre-treatment (45 C for 120 min) on in vitro shoot development of Solanum lycopersicum L. were studied to improve the drought-tolerant of tomato. Morphological, physiological and biochemical changes during the development of in vitro shoot in the drought stress condition were analyzed. Then, leaves of the shoot that pre-treated at 45 C for 120 min and developed on the drought stress condition were cultured on ½ MS medium supplemented with 20 g.L-1 sucrose, 0.1 mg.L-1 Indole acetic acid, 2 mg.L-1 zeatin and 35 g.L-1 mannitol to regenerate the drought-tolerant shoots. In the drought stress condition (½ MS medium with 35 g.L-1 mannitol), the height of shoot, the number of leaves, and the total leaf area were decreased by approximately 50 % compared to control (½ MS medium without mannitol). Besides, the leaf midrib thickness and the vascular bundle width of the leaf in drought stress were smaller than those of the control. The leaf midrib thickness and the leaf vascular bundle width in drought stress condition were 953.30 m and 320.21 m, compared to 1243.80 m and 410.15 m in that of control. Chlorophyll fluorescence occurs in some parenchyma cells near the midrib vascular bundle of treated leaves instead of all parenchyma cells in control leaves. Under the drought stress condition, chlorophyll content, photosynthetic intensity and cytokinin activity of leaf were strongly decreased but respiration intensity, the content of carotenoid and proline, especially the activity auxin and abscisic acid were increased. Thermal pre-treatment stimulated shoot regeneration (2.53 shoots/leaf explant) while there was no shoot regenerated from the leaf of the control plant. The shoots regenerated by this method grew well in the drought stress condition.
... Plants respond and adapt to drought stress through the induction of various morphological and physiological responses [64,65]. Many physiological factors may be involved in drought stress injury [66]. Drought stress can damage the photosynthetic apparatus and decrease leaf chlorophyll content [14], as well as transpiration rate, water content, and leaf angle [15]. ...
Drought stress on plants can cause cellular water deficits and influence the physiology of host plants, which alter the performance of insect pests. This study was conducted to determine the effect of drought and aphid (Myzus persicae Sulzer) infestation on three potato (Solanum tuberosum L) genotypes under greenhouse conditions. A factorial experiment involving three potato genotypes, two levels of drought, and two levels of aphid infestation was conducted. The potato genotypes possessed different levels of tolerance to drought and are described as tolerant (Qingshu 9), moderately tolerant (Longshu 3), and sensitive (Atlantic). Sixty-day-old potato plants were infested with aphid nymphs and monitored for 20 d. There was a significant variety × drought × aphid interaction effect on the parameters measured. The genotype Atlantic, which is sensitive to drought, exhibited greater tolerance to aphid infestation under drought or no drought conditions than the other genotypes. This genotype also exhibited poor host acceptance and the aphid survival rate, colonization success, and average daily reproduction were low. Qingshu 9, which is tolerant to drought, was highly susceptible to aphid infestation and exhibited high host acceptance and greater aphid survival rate, colonization success, and average daily reproduction compared to the other genotypes. This study demonstrates that the biochemical and morphological traits that confer drought tolerance in potato do not necessarily confer aphid tolerance.
... However, antioxidant enzymes Superoxide Dismutase and Peroxidase (POD) levels were increased. [40] Cowpea (Vigna unguiculata L.Walp.) ...
Abiotic stresses arising from climate change negates crop growth and yield, leading to food insecurity. Drought causes oxidative stress on plants, arising from excessive production of reactive oxygen species (ROS) due to inadequate CO2, which disrupts the photosynthetic machinery of plants. The use of conventional methods for the development of drought-tolerant crops is time-consuming, and the full adoption of modern biotechnology for crop enhancement is still regarded with prudence. Plant growth-promoting rhizobacteria (PGPR) could be used as an inexpensive and environmentally friendly approach for enhancing crop growth under environmental stress. The various direct and indirect mechanisms used for plant growth enhancement by PGPR were discussed. Synthesis of 1-aminocyclopropane−1-carboxylate (ACC) deaminase enhances plant nutrient uptake by breaking down plant ACC, thereby preventing ethylene accumulation, and enable plants to tolerate water stress. The exopolysaccharides produced also improves the ability of the soil to withhold water. PGPR enhances osmolyte production, which is effective in reducing the detrimental effects of ROS. Multifaceted PGPRs are potential candidates for biofertilizer production to lessen the detrimental effects of drought stress on crops cultivated in arid regions. This review proffered ways of augmenting their efficacy as bio-inoculants under field conditions and highlighted future prospects for sustainable agricultural productivity.
... Leaves under different treatments were obtained at 1, 40, 50, 60, and 76 days after inoculation to measure chlorophyll content [Chl(a+b)] for three times. [Chl(a+b)] in the leaves was determined using the 96% ethanol immersion method (Ying et al. 2015). A total of 0.1 g of leaves from six seedlings was cut into small pieces (0.2 cm filaments) and extracted with 8 mL of 95% (v/v) alcohol in the dark for 24 h at 25 °C until the leaves were blanched. ...
Plant growth-promoting rhizobacteria (PGPR) are beneficial bacteria that survive within the range of plant rhizosphere and can promote plant growth. The effects of PGPR in promoting plant growth, activating soil nutrients, reducing fertilizer application, and improving the resistance of plant inducible system have been widely investigated. However, few studies have investigated PGPR as elicitors of tolerance to abiotic stresses, especially drought stress. In this study, the effects of Acinetobacter calcoaceticus X128 on the photosynthetic rate (Pn), stomatal conductance (Gs), intracellular CO2 concentration (Ci), and total chlorophyll content [Chl(a+b)] of Sambucus williamsii Hance seedling leaves under moderate drought stress and drought-rewatering conditions were determined. Compared with those of uninoculated seedlings, the average Pn values during the entire drought stress of inoculated seedlings increased by 12.99%. As the drought duration was lengthened, Ci of uninoculated leaves continued to increase after rapidly declining, whereas Gs continuously decreased. Furthermore, their photosynthetic properties were simultaneously restricted by stomatal and non-stomatal factors. After X128 inoculation, Ci and Gs of S. williamsii Hance leaves continued to decrease, and their photosynthetic properties were mainly restricted by stomatal factors. At the end of the drought stress, water stress reduced [Chl(a + b)] of S. williamsii Hance leaves by 13.49%. However, X128 inoculation decreased this deficit to only 7.39%. After water supply was recovered, Pn, Gs, and [Chl(a+b)] in uninoculated leaves were reduced by 14.23%, 12.02%, and 5.86%, respectively, relative to those under well-watered conditions. However, Ci increased by 6.48%. Compared with those of uninoculated seedlings, Pn, Gs, and [Chl(a+b)] in X128-inoculated seedlings were increased by 9.83%, 9.30%, and 6.85%, respectively. Therefore, the inoculation of X128 under arid environments can mitigate the reduction of chlorophyll, delay the restriction caused by non-stomatal factors to Pn in plant leaves under water stress, and can be more conducive to the recovery of photosynthetic functions of leaves after water supply is recovered.
... In our study, CAT activity was increased after elicitor treatment and this increased enzyme activity was noted to be due to H 2 O 2 synthesis, which promotes ROS accumulation in cultivated tissues (Gao et al. 2011). The enzyme activity is considered to be more at the onset of stress and with increasing stress the enzyme activity accumulates further and decreases later/at the end of stress (Ying et al. 2015). ...
Coriandrum sativum is an important spice plant known for its unique fragrance. Coriander oil is also one of the major essential oils in world global market. The oil yield varies with different coriander varieties; and the content and quality of oil is governed by several factors. In recent times, a variety of technologies have been exploited to improve phyto-compounds including essential oils. In this present study, Methyl jasmonate (MeJA) was amended in medium and the yield of essential oil was measured and compared in different cultivating tissues. The cultured tissues were nonembryogenic callus and embryogenic tissues (induction, proliferation and maturation stages of embryos). MeJA acts as a signaling molecule in accumulating secondary metabolites. Four different MeJA treatments i.e. T1 = 50, T2 = 100, T3 = 150 and T4 = 200 μM, along with a control (T0) were used and the yield of coriander essential oil was estimated in different in vitro cultivating tissues by using Gas chromatography–mass spectrometry (GC–MS). The addition of MEJA enriched essential oil yield, maximum oil being in maturation stage of embryos at T3 (150 μM). Other added treatments also had varied stimulatory role. The addition of MeJA induced stress as the stress marker enzymes like superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) content were high compared to non treated tissue (T0). In T4, the CAT activity was maximum i.e. 5.83 and 6.28 mg⁻¹ protein min⁻¹ in Co-1 and RS respectively in matured somatic embryos. The SOD activity was also high at maturation stage of embryos at T4 (5.3 mg⁻¹ protein min⁻¹ in RS). The APX activity on the other, was high (3.32 mg⁻¹ protein min⁻¹) in induction stage of embryogenesis at T3. The comparative biochemical (sugar, protein and proline) analyses of tissues were performed and presented that had high and low essential oil. MeJA induced stress may help in accumulating essential oils in C. sativum.
... Chlorophyll, a photosynthetic pigment, is involved in light absorption and plays an important role in plant photosynthesis. As drought stress can accelerate chlorophyll decomposition, chlorophyll content has been reported as the most frequently used metrics for ascertaining the severity of drought stress (Efeoğlu et al. 2009;Ying et al. 2015). As expected, we observed that the chlorophyll content in DA1 plants significantly decreased under S1 ( Figure 2E). ...
The effects of drought acclimation on plant growth and water relations, membrane status, photosynthetic activity, proline content, membrane lipid peroxidation, enzyme antioxidant activity, and drought-responsive gene expression patterns were investigated under progressive drought conditions with drought acclimation (DA) and non-acclimation (NA) treatments in four wheat genotypes. Initial water stressapplied at 10 days after seedling transfer induced acclimation to subsequent water stress (S2), following re-watering. A reversible decline in plant growth and water relations, membrane stability, and photosynthetic activity resulted in increased lipid peroxidation, reactive oxygen species, membrane injury, enzyme antioxidant activities, and H2O2 and osmolyte accumulation in DA plants. TaWRKY2, TaNAC1, TaMYB2, TabHLH1, and TabZIP1 levels were upregulated to a greater extent in NA than in DA plants, during S2. The results suggest wheat plants employ physiological, biochemical and molecular mechanism under drought improving their ability to survive subsequent water stress in the later period of growth and development.
... Camptothecins are topoisomerase-1 inhibitors, obtained from Camptotheca acuminata, Nyssaceaea, which is native to China. This plant was introduced several times into the USA, and eventually, a few trees were grown at a USDA [139]. There was a screening of the plants collected for various chemical constituents, out of which some extracts were tested for an antibiotic, antitumor and antiviral activity, and the results showed that Camptotheca extracts were the only ones to have high activity, according to a standard test system. ...
Cancer is estimated to be a significant health problem of the 21st century. The situation gets even tougher when it comes to its treatment using chemotherapy employing synthetic anticancer molecules with numerous side effects. Recently, there has been a paradigm shift toward the adoption of herbal drugs for the treatment of cancer. In this context, a suitable delivery system is principally warranted to deliver these herbal biomolecules specifically at the tumorous site. To achieve this goal, carbon nanotubes (CNTs) have been widely explored to deliver anticancer herbal molecules with improved therapeutic efficacy and safety. This review uniquely expounds the biopharmaceutical, clinical and safety aspects of different anticancer herbal drugs delivered through CNTs with a cross-talk on their outcomes. This review will serve as a one-stop-shop for the readers on various anticancer herbal drugs delivered through CNTs as a futuristic delivery device.
... Camptotheca acuminata is native to China and mainly used for extraction of Camptothecin (Ma et al. 2012). This tree is adapted to most soil conditions, such as lightly waterlogged or drought, alkaline or acid soil (Wang et al. 2009, Ying et al. 2015. In addition, we chose this species to extend the research on bicarbonate utilization from our previous study (Rao and Wu 2017). ...
The role of root‐derived dissolved inorganic carbon (DIC) has been emphasized lately, as it can provide an alternative source of carbon for photosynthesis. The fate of newly fixed DIC and its effect on nonstructural carbohydrate (NSC) pools has not been thoroughly elucidated to date. To this end, we used ¹³C (NaHCO3) as a substrate tracer to investigate the incorporation of newly fixed bicarbonate into the plant organs and NSC compounds of Camptotheca acuminata seedlings for 24 and 72 h. NSC levels across the organs were all markedly increased within 24 h of labeling treatment and afterwards only decreased in stems at 72 h. The variation range of NSC concentrations in roots was considerably smaller than in the stem and leaves. As time passed, the δ¹³C in NSC compounds was significantly affected by ¹³C labeling and was more positive in the roots than in the stem and leaves. Starch was more ¹³C‐enriched than was soluble carbohydrate, and the δ¹³C of root starch was as high as ‐4.70‰. Bicarbonate incorporation into newly formed NSC compounds contributed up to 0.24% of the root starch within 72 h. These data provided strong evidence that bicarbonate not only acted as a C source that contributed slightly to the NSC pools but also stimulated the increase in NSC pools. The present study expands our understanding of the rapid change of NSC pools across the organs in response to bicarbonate.
This article is protected by copyright. All rights reserved.
... The possible reason was that, in the seedling stage, compared to the jointing stage, the leaf water potential was higher (Sengupta and Majumder, 2014), the root was shallower, and leaves were smaller, which would result in weaker transpiration and poorer capability of soil water absorption (Kang and Liu, 1993). Thus, more abundant soil moisture was required to maintain high soil water potential to reduce the resistance of water absorption and to ensure water supply in the seedling stage (Ishida et al., 1992;Ying et al., 2015;Zhang et al., 2015). Sadras and Milroy (1996) reviewed soil water thresholds (quantified by plant available water, PAW) of leaf expansion and leaf gas exchange among different species obtained under diverse experimental conditions. ...
The sequence of changes in crop responding to soil water deficit and related critical thresholds are essential for better drought damage classification and drought monitoring indicators. This study was aimed to investigate the critical thresholds of maize growth and physiological characteristics responding to changing soil water and to reveal the sequence of changes in maize responding to soil water deficit both in seedling and jointing stages based on 2-year’s maize field experiment responding to six initial soil water statuses conducted in 2013 and 2014. Normal distribution tolerance limits were newly adopted to identify critical thresholds of maize growth and physiological characteristics to a wide range of soil water status. The results showed that in both stages maize growth characteristics related to plant water status [stem moisture content (SMC) and leaf moisture content (LMC)], leaf gas exchange [net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs)], and leaf area were sensitive to soil water deficit, while biomass-related characteristics were less sensitive. Under the concurrent weather conditions and agronomic managements, the critical soil water thresholds in terms of relative soil moisture of 0–30 cm depth (RSM) of maize SMC, LMC, net Pn, Tr, Gs, and leaf area were 72, 65, 62, 60, 58, and 46%, respectively, in seedling stage, and 64, 64, 51, 53, 48, and 46%, respectively, in jointing stage. It indicated that there is a sequence of changes in maize responding to soil water deficit, i.e., their response sequences as soil water deficit intensified: SMC ≥ LMC > leaf gas exchange > leaf area in both stages. This sequence of changes in maize responding to soil water deficit and related critical thresholds may be better indicators of damage classification and drought monitoring.
... Differences between P134 and P142 at a specific treatment are indicated by asterisk sign. antioxidant enzymes, including SOD and POD has also been reported to be correlated with drought tolerance in other crops (Türkan et al., 2005;Abedi and Pakniyat, 2010;Li et al., 2015;Ying et al., 2015). Besides, CAT, GPX and APX are associated with oxidative tolerance by scavenging of H 2 O 2 (Miller et al., 2010;Gill and Tujeta, 2010). ...
This study was undertaken to unveil the oxidative stress tolerance mechanism in maize seedlings under drought. The level of oxidative stress and involvement of antioxidant and glyoxalase systems were investigated in seedlings of two maize inbreds: P134, a relatively drought tolerant, and P142, a drought susceptible inbred subjected to water deficit for 7 days and then rewatered to reveal the mechanism of oxidative stress tolerance under drought. Water content, chlorophyll (Chl), reactive oxygen species (ROS), lipid peroxidation, methylglyoxal (MG), lipoxygenase (LOX) activity, enzymatic and non-enzymatic antioxidants and glyoxalases status were investigated in the uppermost fully expanded leaves. The superoxide (O2•-) generation rate, hydrogen peroxide (H2O2), lipid peroxidation and MG as well as LOX activity were higher in P142 throughout the drought period. Conversely, relative water content (RWC), Chl, carotenoid (Car) and proline contents were remarkably higher in P134. However, in rewatering, recovery of Chl and Car were higher in P142. The reduced glutathione (GSH), ascorbic acid (ASA) and their redox homeostasis indicated more oxidative damage in P142. The ROS scavenging enzymes like superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) activities were comparatively higher in P142 under drought, while catalase (CAT), monodehydroasacorbate reductase (MDHAR) and glutathione reductase (GR) activities were higher in P134. Though the activity of GST increased in both inbreds, activities of glyoxalase-I (Gly-I) and glyoxalse-II (Gly-II) increased only in P134. In rewatering, activities of most of the enzymes decreased in both inbreds. Taken together, the non-enzymatic antioxidant system was stronger in P134, but the higher SOD, POD, APX, GPX and DHAR activities in P142 suggesting that these enzymes might involve in cellular protection through reducing oxidative damage.
... Of the antioxidative enzymes, peroxidase (POD) catalyses the reduction of H 2 O 2 to water, followed by subsequent oxidation of small molecules (Smith and Veitch, 1998). Drought stress often induces POD activity in many plant species (Jung, 2004;Sofo et al., 2005;Upadhyaya et al., 2008;Selote and Khanna-Chopra, 2010;Ying et al., 2015). The tolerant genotype of maize (Zea mays) exhibited lower accumulation of MDA and H 2 O 2 content related to increasing activities of POD and other antioxidant enzymes under water stress conditions (Moussa and Abdel-Aziz, 2008). ...
Background and aims:
Brachypodium distachyon (Brachypodium) is a model system for studying cereal, bioenergy, forage and turf grasses. The genetic and evolutionary basis of the adaptation of this wild grass species to drought stress is largely unknown. Peroxidase (POD) may play a role in plant drought tolerance, but whether the allelic variations of genes encoding the specific POD isoenzymes are associated with plant response to drought stress is not well understood. The objectives of this study were to examine natural variation of POD isoenzyme patterns, to identify nucleotide diversity of POD genes and to relate the allelic variation of genes to drought tolerance traits of diverse Brachypodium accessions.
Methods:
Whole-plant drought tolerance and POD activity were examined in contrasting ecotypes. Non-denaturing PAGE and liquid chromatography-mass spectrometry were performed to detect distinct isozymes of POD in 34 accessions. Single nucleotide polymorphisms (SNPs) were identified by comparing DNA sequences of these accessions. Associations of POD genes encoding specific POD isoenzymes with drought tolerance traits were analysed using TASSEL software.
Key results:
Variations of POD isoenzymes were found among accessions with contrasting drought tolerance, while the most tolerant and susceptible accessions each had their own unique POD isoenzyme band. Eight POD genes were identified and a total of 90 SNPs were found among these genes across 34 accessions. After controlling population structure, significant associations of Bradi3g41340.1 and Bradi1g26870.1 with leaf water content or leaf wilting were identified.
Conclusions:
Brachypodium ecotypes have distinct specific POD isozymes. This may contribute to natural variations of drought tolerance of this species. The role of specific POD genes in differentiating Brachypodium accessions with contrasting drought tolerance could be associated with the general fitness of Brachypodium during evolution.
... The increase, however, was smaller in the populations of Baneh, Ardabil, and Naim compared with other oregano populations subjected to a moderate water stress, demonstrating that these three oregano populations were more tolerant to water stress than the other studied populations. Ying et al. (2015) have reported large increases in MDA content in two populations of Camptotheca acuminate under water stress. Stress sensitive species exhibit a sharper increase in lipid peroxidation than regular species under water deficit stress (Liu et al., 2011;Khoshro et al., 2013;Shanjani et al., 2014). ...
Abstract
Oregano (Origanum vulgare), a popular flavoring herb, is widely used throughout the world for flavoring foods and beverages. Water stresses in the arid and semiarid regions of the Middle Eastern countries, however, severely limit growth, production, and survival of oregano. To determine the growth and ecophysiological responses of native Iranian oregano to prolonged water stress, six populations sourced from different bioclimatic zones in Iran were studied. The plants, grown in pots, were subjected to three water stress conditions, no water stress, mild water stress, and moderate water stress, which were continuously maintained throughout the entire plant development and growth period. Relative water content, cellular injury, leaf pigmentation, proline content, leaf area, biomass production, and antioxidant enzymes (peroxidase, ascorbate peroxidase, catalase, and superoxide dismutase) were monitored. The relative plant yield, water content, pigmentation, and leaf area were reduced under water stress, although the ratio of carotenoids to total chlorophyll in the studied populations was increased. Under the prolonged water stress conditions, three oregano populations exhibited higher plant yield along with higher levels of proline accumulation and increased activity of catalase, superoxide dismutase, and peroxidase along with smaller increases in ion leakage and malondialdehye content than other populations. The positive relationship was observed among activity of superoxide dismutase (SOD) and proline content, however, the correlation result showed a negative relationship between ion leakage and activity of SOD. Our results indicated that populations of Baneh, Ardabil, and Namin had a higher tolerance to water deficit conditions than other investigated populations of oregano.
... Decrease in relative water content (RWC) is one of the early symptoms of water deficiency in plant tissues [6]. Relative water content is crucial to optimum physiological functioning and growth processes [7]. Canopy temperature is dependent on climatic parameters and internal plant water status. ...
Water is the most limiting factor in plant production in most parts of the world, especially in arid and semiarid regions. Thus, a field experiment based on randomized complete block design with three replications was conducted in 2013 to investigate some properties of borage leaves at vegetative stage in response to water limitation. Treatments were four levels of irrigation (irrigation after 60, 90, 120 and 150 mm evaporation from class A pan). Result indicated that the effect of irrigation intervals on leaf area index and relative water content of borage was not significant. However, leaf temperature of borage under moderate and severe water stress was 3.2 and 4.1oC higher than that under well watering. Electrolyte leakage and chlorophyll content index were also increased with decreasing water availability. It was concluded that borage is a tolerant plant to water stress at vegetative stage.
Taraxacum kok-saghyz has been identified as one of the most promising alternative rubber crops, with laticifer cells that produce high-quality rubber. To uncover the underlying molecular mechanisms regulating natural rubber biosynthesis under MeJA induction, a reference transcriptome was constructed from nine samples of T. kok-saghyz. MeJA treatment was applied for 0 h (control), 6 h, and 24 h. A total of 7452 differentially expressed genes (DEGs) were identified in response to MeJA stress, relative to the control. Functional enrichment showed that these DEGs were primarily related to hormone signaling, defensive responses, and secondary metabolism. Combined analysis of the DEGs induced by MeJA and high-expression genes in laticifer cells further identified seven DEGs related to natural rubber biosynthesis that were upregulated in latex tissue, suggesting that these candidate genes could prove valuable in studying the mechanism of MeJA-mediated natural rubber biosynthesis. In addition, 415 MeJA-responsive DEGs were from several transcription factor families associated with drought resistance. This study helps to elucidate the mechanism of natural rubber biosynthesis in T. kok-saghyz in response to MeJA stress and identifies key candidate MeJA-induced DEGs in laticifer tissue, as well as a candidate drought-response target gene , whose knowledge will promote the breeding of T. kok-saghyz in the aspect of rubber yields and quality, and drought tolerance.
Purpose
The purpose of this study is to explore a balanced understanding of the relationship between perceived occupational stigma and social workers’ proactive behaviors in China. Drawing on cognitive appraisal theory, this study explored the mediating role of threat and challenge appraisals, as well as the moderating role of trait resilience.
Design/methodology/approach
Data were collected using a time-lagged research design. The hypotheses were examined using a sample of 338 social workers in China.
Findings
Perceived occupational stigma is appraised as both a challenge and a threat simultaneously. Challenge appraisal positively mediated perceived occupational stigma and proactive behavior, whereas threat appraisal negatively mediated this relationship. Trait resilience moderated the effect of threat appraisal, suggesting that perceived occupational stigma was appraised as a threat when trait resilience was lower (rather than higher), which then reduced social workers’ proactive behaviors.
Originality/value
This study enriches the literature on perceived occupational stigma by identifying the relationship and mechanism of perceived occupational stigma-proactive behaviors and a boundary condition from the theoretical perspective of cognitive appraisals. It demonstrates both the positive and negative aspects of perceived occupational stigma as appraised by social workers in relation to an important workplace outcome of proactive behaviors. In addition, it offers a fresh approach by exploring perceived occupational stigma from the perspective of social workers.
This study was conducted to determine the aphicidal effect of a leaf extract of the Atlantic potato cultivar on the performance of green peach aphids. Three concentrations of the leaf extract (100, 75, and 50% potato extract), synthetic pesticide (Beta cypermethrin 4.5%), and distilled water (control) treatments were applied in a greenhouse experiment. The results showed that the synthetic pesticide, which was used as a standard check, caused the maximum aphid mortality, followed by the 100% potato leaf extract. Compared with the other botanical treatments, the 100% extract produced low mean rates of survival, aphids’ average daily reproduction, the number of nymphs per plant, and the number of nymphs per adult. This treatment also increased the accumulation of hydrogen Peroxide (H2O2) and malondialdehyde (MDA), glutathione-s-transferase, mixed-function oxidase, and carboxylesterase content in the green peach aphid. Moreover, the 100% extract also protected the host plants against green peach aphid attacks by demonstrating higher chlorophyll content, net photosynthesis, above-ground fresh weight, and above-ground dry weight of the host plant. This study demonstrates that the highest concentration of potato (Atlantic cultivar) leaf extract (100% extract) could be used as the appropriate dosage for the control of green peach aphids on potatoes, which could greatly reduce the use of synthetic insecticides and promote ecosystem sustainability.
Medicinal and Aromatic Plants Research Station and Department of Agricultural Biotechnology, Anand Agricultural University, Gujarat, conducted the experiment in May 2019 to determine the physiological and differential gene expression analysis of teak seedlings under various abiotic stress conditions (control, 150 mM NaCl and 15% PEG). The physiological data [chlorophyll content, membrane stability index and relative water content] were recorded at 0, 2, 7, and 12 DAT with four repetitions. These parameters were all lowered quantitatively at first, and then considerably during longer treatment. The application of 150 mM NaCl has disastrous effects on plant physiology in terms of PEG. The findings revealed that diverse stresses have a substantial impact on seedling physiology due to chlorophyll degradation, cell and chloroplast membrane damage, ROS formation, and decreased water absorption in response to physiological or physical shortage of accessible soil moisture. At 12 DAT, the gene expression profile of treated seedlings was compared to that of control seedlings. RT-PCR was used to examine the expression of one endogenous and ten stress-related genes. MYB-3 , HSP-1 , BI-1 , and CS-2 genes were up-regulated in leaves of stress-treated seedlings. The genes' up-regulation supported their protective role in plants under abiotic stress. Treatments, stress duration, and plant species all altered the expression profile of genes. According to the findings of this study, these physiological indicators could be used as marker indices to measure tree's stress tolerance capacity during the seedling stage. The up-regulated genes will be further investigated and used to confirm stress resistance and susceptible teak seedlings.
The comprehension of the precise water consumption of agricultural crops is a valuable tool for establishing management programs and irrigation schedules. Appropriately, the purpose of this study was to promote a bibliographic review on the main reflexes of the inappropriate use of water and what this process can promote in the establishment and development of agricultural crops. Moreover, theoretical questions were raised regarding physiological responses triggered by soil water deficit and its effect on crop growth, critical periods for water deficit, physiological responses, and their effects on the growth of main agricultural crops. Information on the misuse of water resources and its effects have presented a series of manifestations to plants and, consequently, to agricultural production, such as a production depletion, reduction of carbon fixation, nutritional deficiency, reduction of plant height, reduction of thousand-grain weight, yellowing of leaves, reduction in germination percentage, among other factors. Correspondingly, water stress can cause a drastic reduction in leaf area, productivity decrease, stomatal closure, leaf senescence, reduced roots, reduced flowering, hampering crop emergence and stability, spikelet sterility, etc. Finally, studies aimed at the consequences of poor irrigation and/or inadequate precipitation values are of high importance, mainly due to the investigative improvement on the use of water in an effective and sustainable way.
Introduction In fact, drought is stress that restricts the plant photosynthesis and causing changes in the chlorophyll content and damage to photosynthetic structures. One of the important reasons that environmental stresses such as drought reduce the growth and photosynthesis ability of the plant is a disturbance in the balance between production and removal of free oxygen radicals. Transpiration is a necessary process for photosynthesis and growth of plants but depending on the conditions may be harmful in some cases, so that the use of anti-transpirant can be one of the most effective methods for reducing the amount of water lost through transpiration and effective way to reduce the effects of drought stress on plants and adjustment the reduction of the yield due to water deficiency in arid and semi-arid regions. Climate change created in the world and the intensification of stresses caused by it, especially drought stress in arid and semi-arid regions such as Iran, make it difficult to achieve this goal. Therefore, finding strategies that can reduce the effects of water shortages on plant growth and yield and improve growth and yield can be very important. The aim of the present study was to investigate the effect of irrigation regimes and application of different concentrations of tragacanth (naturally dried exudate from some Astragalus species) on black cumin plant.
Materials and Methods This research was carried out in a factorial experiment based on completely randomized design with three replications in a greenhouse of the Agriculture College of Kurdistan University in 2018. The experimental factors were including irrigation at three levels of 100% (full irrigation), 70% (mild drought stress), and 40% (severe drought stress) of field capacity of soil and spraying with tragacanth extract at six concentrations of 0, 1.25, 2.5, 5, 7.5, and 10 g/L. Spraying of this material was done using a back sprayer (Shark model) with a constant pressure of 2.4 bar and a volume of 250 liters of water per hectare. Before the data were analyzed, their normality test was performed using the Mini Tab software. After ensuring the normality of data, analysis of variance was performed using SAS ver. 9.3. LSD (Least significant difference) was used to compare the mean of treatments. The graphs are drawn using Excel software.
Results and Discussion The results showed that increased drought stress intensity (irrigation reduction) led to the reduced leaf relative water content, Total chlorophyll content, efficiency of photosystem II, plant hight, number of capsules per plant, mean number of seeds per plant, biological yield and grain yield. The positive effects of tragacanth consumption on reducing and modifying the effects of drought stress on different levels of irrigation and different concentrations of tragacanth were different. In the present study, under full irrigation conditions, lower concentrations of tragacanth were useful, while in drought stress conditions, higher concentrations of tragacanth (except 10 g/L) were useful. In full irrigation, the concentration of 1.25 g/L was positive for all studied traits. In mild drought stress, the use of higher concentrations of tragacanth up to 5 g/L had the best effect and more concentrations resulted in a reverse effect on studied traits. In severe drought stress, the use of more concentrations of tragacanth extract was beneficial and improved the studied traits up to 7.5 g/L, but 10 g/L had a negative effect on these traits. Considering the effect of proper concentration of this material on the improvement of measured traits and increasing the grain yield compared to non-application of tragacanth under severe and moderate drought stress conditions by 11.6% and 28.2%, respectively.
Conclusion The results of this study indicated the different effects of various concentrations of tragacanth material in different levels of irrigation on studied traits of black cumin. Therefore, it can be concluded that the application of different concentrations of tragacanth gum was completely dependent on the plant's water status. So that, using higher concentrations of tragacanth gum in drought stress conditions had a more positive effect on the plant, and vice versa, using a lower concentration of this material was useful in full irrigation. The effect of tragacanth gum on reducing and modifying the effects of drought stress in different plants requires further studies and extensive research. Tragacanth gum can be introduced as a new anti-transpirant agent with natural origin and its application can be useful and recommended in areas exposed to drought stress.
Reactive oxygen species (ROS) originate as a natural byproduct in standard metabolism of oxygen activities. The principal sites of ROS generation in the cell are apoplast, mitochondria, chloroplasts, and peroxisomes. These ROS can induce cellular injuries by proteins oxidation, lipid peroxidation, and DNA damage, which finally may result in plant cellular death. Under regular circumstances, there is a steadiness between generation and elimination of ROS, but this balance is hampered by different biotic and abiotic stress factors such as exposure to heavy metals, high and low-light conditions, pathogens, insects and temperature extremes, resulting in a high generation of ROS which should be counteracted by the antioxidant machinery in cells. The antioxidant system of defense is composed by two groups: (i) Enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), general peroxidases (PRX) (e.g. guaiacol peroxidase GPX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR); (ii) Non-enzymatic antioxidants such as ascorbic acid (AA), reduced glutathione (GSH), α-tocopherol, carotenoids, plastoquinone/ubiquinone and flavonoids. These two groups of metabolites and enzymes work together with the main aim of ROS scavenging, but also in determining plant signaling, immune response, and plant growth and development. Finally, the molecular genetics of ROS genes and related metabolic pathways are briefly outlined, including gene isoforms, cellular localization, The Botanical Review https://doi.org/10.1007/s12229-020-09231-1 Author's personal copy detection methods used and interactions amongst them. This information is crucial in better understanding and designing procedures for plants´stress tolerance; leading to a better management of agricultural plants under challenging and changing climatic conditions and food security.
Drought is one of the critical factors limiting tree growth and survival. Clarifying the adaptation to drought will facilitate the cultivation of drought‐tolerant varieties. Metabolites, as direct signatures of biochemical functions, can uncover the biochemical pathways involved in drought responses. Here, we investigated the physiological and metabolic responses of drought‐tolerant Populus simonii and drought‐susceptible P. deltoides cv. ‘Danhong’ to drought. Under drought conditions, P. simonii grew better and had a higher photosynthetic rate than P. deltoides cv. ‘Danhong’. Global untargeted metabolite profiling was analyzed using gas chromatography time‐of‐flight mass spectrometry system. A total of 69 and 53 differentially accumulated metabolites were identified in drought‐stressed P. simonii and P. deltoides cv. ‘Danhong’, respectively. The metabolisms of carbohydrate, amino acid, lipid and energy were involved in the drought responses common to both poplar species. The citric acid cycle was significantly inhibited to conserve energy, whereas multiple carbohydrates acting as osmolytes and osmoprotectants were induced to alleviate the adverse effects of drought stress. Unlike P. deltoides cv. ‘Danhong’, P. simonii underwent a specific metabolic reprogramming that enhanced non‐enzymatic antioxidants, coordinated the cellular carbon/nitrogen balance, and regulated wax biosynthesis. These results provide a reference for characterizing the mechanisms involved in poplar response to drought and for enhancing the drought tolerance of forest trees. This article is protected by copyright. All rights reserved.
Camptotheac acuminata Decne is a unique tree species in China with an important secondary metabolite, camptothecin (CPT), used in the treatment of cancer. Nitrogen (N) is an important element that affects plant growth and the accumulation of CPT. Reports on the effect of N on CPT synthesis from a genetic perspective are scarce. To explore the effects of different N sources and levels on CPT synthesis in C. acuminata, two-year-old seedlings were fertilized with different concentrations of pure ammonium sulphate, source of ammonium N (NH4⁺–N), and potassium nitrate for nitrate N (NO3⁻–N). Concentrations of 2.5, 5, 7.5, and 10 g pot⁻¹ NH4⁺–N and NO3⁻–N were used. The results showed that 7.5 g NH4⁺–N and NO3⁻–N treatments were best for growth and fresh weight of leaves. Compared with the other treatments, the CPT content, tryptophan synthase and tryptophan decarboxylase activities, and expression of the CaTSB and CaTDC1 genes under the 2.5 g NH4⁺–N and NO3⁻–N treatments peaked significantly at 30 days. However, the expression of CaTDC2 surpassed that of the other two genes at 60 days. Therefore, compared with NH4⁺–N source, the NO3⁻–N source was more beneficial for growth, and NO3⁻–N was better for CPT yield. Consequently, leaves of C. acuminata treated with 2.5 g NO3⁻–N could be harvested after 30 days to obtain maximum CPT content. CaTDC1 is more closely linked to CPT synthesis. The results of this study improved the production of CPT in C. acuminata via fertilization.
In order to characterize the response to drought of 19 ethyl methanesulfonate (EMS)-mutagenized lines of durum wheat (Triticum durum Desf.) derived from the variety CHAM-1 and cultivated in Morocco, growth (plant height, PLH) and yield (grain number per spike, GNS) parameters were followed for different lines and CHAM-1 variety. All were cultivated under well-watered (C) and drought conditions (T). In parallel, quantitative and qualitative aspects of leaf peroxidases (EC 1.11.1.7) were analyzed. When compared with C plant lines, the corresponding T lines showed decreases of 9–38% and 1–78%, respectively, for PLH and GNS parameters. A positive correlation was found between PLH and the yield as GNS (r² = 0.885). When expressed as units mg⁻¹ proteins, soluble peroxidases (SPOX) were less represented than the ionically wall-bound peroxidases (IPOX) in all mutagenized wheat lines, with 22.1% and 46.2% as respective coefficients of variation for drought-stressed lines. Drought-induced reduction in grain yields for all lines correlated positively with percentages of IPOX exhibited by stressed plants (r² = 0.68). In addition, Averages of drought-induced decreases in GNS, calculated for five groups of mutagenized lines, were found to be positively correlated with their respective percentages of IPOX (r² = 0.906). Drought-adapted lines showed decreases in IPOX. When subjected to electrophoresis using 6–15% polyacrylamide gradient gels, resolved IPOX of cereal line groups of limited drought-induced reduction in GNS exhibited low reactivity on native gels. These data support the hypothesis that IPOX are indicators of the sensitivity of wheat lines to drought conditions. Possible mechanisms of POX involvement in wheat resistance to drought and developing appropriate biochemical tests to screen variability and drought adaptation of EMS mutants are discussed in this study.
Locally adapted trees and shrubs are suggested to show higher fitness at their site of origin than non-locally adapted ones. The production in tree nurseries could take this into account to improve outplanting performance. However, separate production of specific ecotypes in nurseries increases the costs of production and may reduce the availability of a specific species. In this study, we investigated drought stress reactions of 2 year-old container-grown seedlings of Quercus robur L. and Tilia cordata Mill. from four and three different populations, respectively, each from a different site of origin. Slow- and fast-developing drought stress treatments were applied in a greenhouse study to determine any difference in drought tolerance. Control plants were well irrigated. Depending on the species and stress development, only marginal interpopulation differences in particular physiological (pre-dawn water potential, stomatal conductance, relative water content) and/or biochemical (glucose, fructose, sucrose, starch, proline) reactions to drought existed. These differences did not consistently reflect precipitation conditions at the population sites of origin, indicating only low level of local adaptation for populations of the target species.
Index words: adaptation, carbohydrates, pedunculate oak, provenances, proline, small-leaved lime.
Species used in this study: pedunculate oak (Quercus robur L.); small-leaved linden (Tilia cordata Mill.).
Methyl jasmonate (MeJA) is a naturally occurring plant growth regulator and play vital roles in plant defense and many developmental processes such as root growth and seed germination. This study was undertaken to study the possible role of using methyl jasmonate to alleviate the adverse effect of water stress on soybean genotypes (Giza 22 and 35). The results showed that water stress reduced shoot length, fresh and dry weights of shoot and root, photosynthetic pigments, relative water content and oil content in the shoots of all soybean genotypes. On the other hand, there was a considerable increase in cell wall fractionation, saturated and unsaturated fatty acids, flavonoids, phenolic acid and sugar fraction content in the shoots of the soybean genotypes in response to the water stress. Foliar spray with methyl jasmonate increased all the above parameters as compared to stressed plants. The results investigate the important role of MeJA in alleviation of water stress in soybean plants and suggest that MeJA could be used for improving plant growth under water stress as a potential growth regulator. The soybean genotypes Giza 22 was found to be more resistant to water stress than Giza 35. © 2017 Prof. H.S. Srivastava Foundation for Science and Society
Drought and heat stresses are important threat limitations to plant
growth and sustainable agriculture worldwide. Our objective is to
provide a review of plant responses and adaptations to drought and
elevated temperature including roots, shoots, and final yield and
management approaches for alleviating adverse effects of the stresses
based mostly on recent literature. The sections of the paper deal with
plant responses including root growth, transpiration, photosynthesis,
water use efficiency, phenotypic flexibility, accumulation of compounds
of low molecular mass (eg proline and gibberellins), and expression of
some genes and proteins for increasing the tolerance to the abiotic
stresses. Soil and crop management practices to alleviate negative
effects of drought and heat stresses are also discussed. Investigations
involving determination of plant assimilate partitioning, phenotypic
plasticity, and identification of most stress-tolerant plant genotypes
are essential for understanding the complexity of the responses and for
future plant breeding. The adverse effects of drought and heat stress
can be mitigated by soil management practices, crop establishment, and
foliar application of growth regulators by maintaining an appropriate
level of water in the leaves due to osmotic adjustment and stomatal
performance.
The changes in plant growth, relative water content (RWC), stomatal conductance, lipid peroxidation, proline and antioxidant system in relation to the tolerance to polyethylene glycol mediated water stress were investigated in drought-sensitive common bean P. vulgaris L. accession FM 53 and drought-tolerant tepary bean P. acutifolius Gray accession PI 321–638. For induction of water stress, the 35 days old bean seedlings were subjected to PEG 6000 of osmotic potential À0.40 MPa for 14 days. With regard to vegetative growth, PEG treatment caused more decrease in P. vulgaris than in P. acutifolius indicating a superior performance of wild species under water stress. Root and shoot DW increased in P. acutifolius while decreased in P. vulgaris on day 14. PEG treatment had no effects on relative water content (RWC) in P. acutifolius but, reduced RWC in P. vulgaris. P. acutifolius maintained a greater stomatal conductance than P. vulgaris under water stress imposed by PEG treatment. In P. acutifolius constitutive level of lipid peroxidation was lower than in P. vulgaris and did not change at the end of the experiment. Constitutive activities of SOD, CAT, APOX and POX were higher in P. acutifolius than in the sensitive one and SOD, APOX and GR activities showed an enhancement in the former under water stress. Proline accumulation was also higher in P. acutifolius than in P. vulgaris both under control and water stress conditions. These results possibly suggest that the drought-tolerant tepary bean P. acutifolius showed a better protection mechanism against oxidative damage by maintaining higher constitutive and induced activities of antioxidant enzymes, than the sensitive common bean P. vulgaris.
Reactive oxygen species (ROS) are produced as a normal product of plant cellular metabolism. Various environmental stresses lead to excessive production of ROS causing progressive oxidative damage and ultimately cell death. Despite their destructive activity, they are well-described second messengers in a variety of cellular processes, including conferment of tolerance to various environmental stresses. Whether ROS would serve as signaling molecules or could cause oxidative damage to the tissues depends on the delicate equilibrium between ROS production, and their scavenging. Efficient scavenging of ROS produced during various environmental stresses requires the action of several nonenzymatic as well as enzymatic antioxidants present in the tissues. In this paper, we describe the generation, sites of production and role of ROS as messenger molecules as well as inducers of oxidative damage. Further, the antioxidative defense mechanisms operating in the cells for scavenging of ROS overproduced under various stressful conditions of the environment have been discussed in detail.
Publisher Summary This chapter presents detailed information on chlorophylls and carotenoids to give practical directions toward their quantitative isolation and determination in extracts from leaves, chloroplasts, thylakoid particles, and pigment proteins. The chapter focuses on the spectral characteristics and absorption coefficients of chlorophylls, pheophytins, and carotenoids, which are the basis for establishing equations to quantitatively determine them. Therefore, the specific absorption coefficients of the pigments are re-evaluated. This is achieved by using a two-beam spectrophotometer of the new generation, which allows programmed automatic recording and printing out of the proper wavelengths and absorbancy values. Several procedures have been developed for the separation of the photosynthetic pigments, including column (CC), paper (PC), and thin-layer chromatography (TLC) and high-pressure liquid chromatography (HPLC). All chloroplast carotenoids exhibit a typical absorption spectrum that is characterized by three absorption maxima (violaxanthin, neoxanthin) or two maxima with one shoulder (lutein and β-carotene) in the blue spectral region.
Viticulture is strongly conditioned by water availability in many areas and this limitation increases according to climatic
change predictions. Maximizing grape
water use efficiency
(WUE) has become a key objective in management practices as well as a target for new environmental friendly cultivars. The
goals of this chapter are to define the different spatial and temporal scales at which WUE can be measured and to describe
the presently available methodologies to perform these determinations. Three different levels of WUE are distinguished: Vineyard
or Crop (WUEc), Plant (WUEp) and Leaf (WUEl). The meaningful of the different WUE parameters depends on the objective of the study and the methodology used. Positive
and negative implications of the available methodologies to measure or estimate WUE at the different spatial and temporal
scales are discussed, as well as the existing relationships between these different parameters to estimate WUE.
In this study, the gas exchange, chlorophyll fluorescence, and antioxidant activity in eight tall fescue cultivars were investigated under aluminum stress. The results showed that the net photosynthetic rate (P
N) and stomatal conductance (g
s) were decreased, while the intercellular CO2 concentration (Ci) was stable or increased under Al stress conditions. The efficiency of excitation capture by open PSII reaction centers (F′v/F′m), the maximum quantum yield of PSII photochemistry (F
v/F
m), the quantum yield of PSII electron transport (ΦPSII), and the photochemical quenching (qP) were also decreased after Al stress, while the non-photochemical quenching (NPQ) was increased. Moreover, Al stress increased the antioxidant activities and MDA contents in each tall fescue cultivars. However, there was a lot genotype differences between the Al-tolerant and Al-sensitive cultivars. Cv. Barrington was the most sensitive cultivar and cv. Crossfire 2 was the most tolerant cultivar. The excessive excitation energy could not be dissipated efficiently by antenna pigments, and reactive oxygen species could not be scavenged efficiently, thereby resulting in membrane lipid peroxidation in cv. Barrington under Al stress conditions.
To identify scorable marker traits that can be used in cereal breeding programs for selecting drought tolerant individuals,
we investigated the correlation among the drought-associated traits in two F2 populations derived from the crosses made between drought tolerant and sensitive barley and wheat parental genotypes. The
parental genotypes of these crosses also differed by at least three other traits – paraquat tolerance, leaf size, and the
relative water content. These three traits were scored in two F2populations of 80 individuals for each barley and wheat cross. Analysis of results indicated that the enhanced tolerance to
paraquat was correlated with reduced leaf size and increased relative water content, two traits associated with water stress
phenotypes of the drought tolerant barley and wheat parents. Our results suggested that the selection based on paraquat tolerance
istechnically less demanding and thus useful for rapid screening of individuals for enhanced drought tolerance in segregating
populations.
The leaf is an important plant organ, and how it will respond to future global warming is a question that remains unanswered. The effects of experimental warming on leaf photosynthesis and respiration acclimation has been well studied so far, but relatively little information exists on the structural and biochemical responses to warming. However, such information is very important to better understand the plant responses to global warming. Therefore, we grew Arabidopsis thaliana at the three day/night temperatures of 23/18°C (ambient temperature), 25.5/20.5°C (elevated by 2.5°C) and 28/23°C (elevated by 5°C) to simulate the middle and the upper projected warming expected within the 21st century for this purpose.
The 28/23°C treatment significantly reduced the life span, total biomass and total weight of seeds compared with the other two temperatures. Among the three temperature regimes, the concentrations of starch, chlorophyll, and proline were the lowest at 28/23°C, whereas the total weight of seeds, concentrations of chlorophyll and proline, stomatal density (SD), stomatal conductance (gs), net CO2 assimilation rate (A) and transpiration rate (E) were the highest at 25.5/20.5°C. Furthermore, the number of chloroplasts per cell and mitochondrial size were highest at 25.5/20.5°C and lowest at 28/23°C.
The conditions whereby the temperature was increased by 2.5°C were advantageous for Arabidopsis. However, a rise of 5°C produced negative effects, suggesting that lower levels of warming may benefit plants, especially those which belong to the same functional group as Arabidopsis, whereas higher levels of warming may produce negative affects. In addition, the increase in A under moderately warm conditions may be attributed to the increase in SD, chlorophyll content, and number of chloroplasts. Furthermore, starch accumulation in chloroplasts may be the main factor influencing chloroplast ultrastructure, and elevated temperature regulates plant respiration by probably affecting mitochondrial size. Finally, high SOD and CAT activities may enable plants grown at elevated temperatures to exhibit relatively high tolerance to temperature stress, thus alleviating the harmful effects of superoxide anion radicals and hydrogen peroxide.
Development of corn (Zea mays L.) germplasm tolerant to water stress will be vital to sustaining corn-based farming in the U.S. Great Plains. In a companion 4-yr field study near Shelton, NE, we found that 12 hybrids displayed differential agronomic responses to varying water levels, with tolerant hybrids yielding from 27 to 42% more than susceptible hybrids under stress while yielding similarly under no stress. The objective of this study was to determine if chlorophyll fluorescence (CF) measurements could be used to distinguish tolerant from susceptible hybrids. Leaf temperature (LT) and two CF parameters (phi(PSII), photosystem II quantum efficiency, and ETR, electron transport rate) were measured on three postflowering dates in 2001 using a fluorometer on a subset of original treatments involving two tolerant and susceptible hybrids grown under deficit and adequate water. Water effects were observed on only one date; LT was 2.5 degrees C warmer and phi(PSII) and ETR values were 25% lower for deficit vs. adequate water just after silking, signifying increased water stress and decreased photosynthesis during reproductive growth. Under stress, LTs were 2.8 degrees C cooler and phi(PSII) and ETR values 50% higher for tolerant vs. susceptible hybrids, while all hybrids produced similar CF values under no stress. Thus, grain yield and photosynthetic responses of hybrids to stress were similar, indicating that CF measurements can be used to distinguish tolerant from susceptible hybrids.
Several reactive oxygen species (ROS) are continuously produced in plants as byproducts of aerobic metabolism. Depending on the nature of the ROS species, some are highly toxic and rapidly detoxified by various cellular enzymatic and nonenzymatic mechanisms. Whereas plants are surfeited with mechanisms to combat increased ROS levels during abiotic stress conditions, in other circumstances plants appear to purposefully generate ROS as signaling molecules to control various processes including pathogen defense, programmed cell death, and stomatal behavior. This review describes the mechanisms of ROS generation and removal in plants during development and under biotic and abiotic stress conditions. New insights into the complexity and roles that ROS play in plants have come from genetic analyses of ROS detoxifying and signaling mutants. Considering recent ROS-induced genome-wide expression analyses, the possible functions and mechanisms for ROS sensing and signaling in plants are compared with those in animals and yeast.
Key message SA treatment effectively ameliorated the negative effect of moderate drought stress on T. grandis Seedlings through increasing the water content, Pn, proline content, antioxidant enzymes activity and reducing MDA. Abstract Water availability is one of the most critical factors that limits the growth and development of plants. Salicylic acid (SA) is an important signal molecule that modulates plant responses to abiotic stress. To elucidate the regulating mechanism of exogenous SA on Torreya grandis cv. Merrillii under different water stresses, a pot experiment was conducted in a greenhouse. Exposure of T. grandis seedlings to drought conditions resulted in reduced growth rate that was associated with a decline in water content and CO2 assimilation. Foliar application of SA effectively increased the water content, net CO2 assimilation rate, proline content and antioxidant enzymes activity in the plants, which helped T. grandis to acclimate to moderate drought stress and increase the shoot dry matter. However, when the plants were under severe drought stress, the relative water content and CO2 assimilation in the SA-treated plants were significantly lower than those in the control plants. Therefore, our results indicated that SA can effectively ameliorate the negative effect of moderate drought stress on T. grandis seedling growth.
Plant tissue deterioration is of prime importance to food and horticultural scientists. Experimental evidence continues to be gathered supporting membrane damage as the key event leading to a cascade of biochemical reactions culminating in tissue deterioration and economic loss. In this paper, the sequence of occurrences in plant membranes during natural senescence and resulting from postharvest stresses are reviewed and compared. The picture emerging from numerous studies devoted to this topic is of membrane lipids undergoing extensive chemical degradation. Biophysical changes in membrane lipids and enzymatic and non-enzymatic lipid peroxidation leads to altered membrane properties and result in defects such as ion leakage and cellular decompartmentation. Postharvest stresses including chilling injury and freezing injury often lead to similar patterns of deterioration. However, it is too early to conclude positively that a truly universal mechanism for both senescence and postharvest stress-induced membrane damage exists.
Six cultivars of safflower which were (PI-387820, PI-251978, PI-170274, PI-387821, PI-386174 and Thori-78) grown in net house of NIAB under salinity (10 ds m-1) and drought (60% field capacity) conditions and compared to their oxidative damage and antioxidative responses. Plant samples (leaves) were collected for the determination of malonidialdehyde (MDA), antioxidative enzymes (catalase, ascorbate peroxidase, glutathione reductase, and peroxidase), proline, and photosynthetic pigments. Salinity and drought decreased the chlorophyll a and b contents but a decrease in chlorophyll a and b was less in safflower variety (THORI-78) which could be a useful marker for selecting a stress tolerant variety. Both stresses considerable increases the accumulation of proline in PI-251978, PI-170274, PI-387821, PI-386174 and THORI-78 varieties of safflower whereas the proline accumulation did not appear to be an essential part of the protection mechanism against salinity and drought in variety PI-387820. Enzyme activity measurements revealed that THORI-78 can tolerate salinity and drought stress well by increasing the activity of catalase and APX enzymes whereas variety PI-386174 showed increased activity of glutathione reductase enzyme under salinity and drought and appear to be very crucial antioxidative defenses during intense stress conditions. The results indicate that the photosynthetic pigments, proline and activities of the enzymes are important mechanism for the stress tolerance in safflower plant and can be considered as genetic improvement for the plant in salinity and drought soil conditions.
summaryTwo families of Helianthus lines, T−S (low desiccation rate) and T+ (low desiccation rate), with contrasting osmotic adjustment (OA), obtained from a divergent selection programme, were compared for several morphological traits, ecophysiological parameters and molecular markers. The physiological analysis in a glasshouse experiment showed that the two families were identical in irrigated conditions except for a single trait, relative water loss (RWL: water loss rate of excised leaves). RWL could be used for these genotypes as a physiological marker of OA. A molecular analysis of the two contrasting lines, using differential screening of cDNA libraries, led to the isolation of three specific cDNAs, one of which, DRS26, showed high sequence homology with a mammalian amino-acid transporter. Subsequent RFLP and STS studies, using DRS26 and RAPD bulked analysis, enabled the identification of putative molecular markers of RWL and OA in T−:T+ sunflower.
Camptotheca acuminata plantations were established in southern Louisiana in an effort to provide raw plant materials for deriving camptothecins, compounds having antitumor activity. This study was conducted to evaluate the growth and camptothecin distribution within the trees. It was found that all plant parts contained camptothecins following 1 year of growth in the field. Branches, roots, and stems accumulated significantly higher concentrations of camptothecins than leaves. Bark was significantly higher in camptothecin concentration than wood. Younger and older tissues within a growing season were not significantly different in camptothecin concentrations. High correlation in camptothecin concentration was found between branch and stem, root and stem, and root and branch, whereas little correlation was observed between bark and wood, and leaf and any other plant component. Field-grown C. acuminata has the observed characteristic of multiple current-year branching. The proportion of bark in term of dry weight and dimension decreased as trees increased in diameter. Dried shoots (bulk) contained 0.042% camptothecin, and dried roots (bulk) contained 0.051% camptothecin. Keywords: Camptotheca acuminata, medicinal plants cultivation, camptothecin content, camptothecin distribution, biomass.
Adaptation to water stress has determined the evolution and diversification of vascular plants. Water stress is forecasted to increase drastically in the next decades in certain regions, such as in the Mediterranean basin. Consequently, a proper knowledge of the response and adaptations to drought stress is essential for the correct management of plant genetic resources. However, most of the advances in the understanding of the molecular response to water stress have been attained in angiosperms, and are not always applicable to gymnosperms. In this work we analyse the transcriptional response of two emblematic Mediterranean pines, Pinus pinaster and Pinus pinea, which show noticeable differences in their performance under water stress. Using microarray analysis, up to 113 genes have been detected as significantly induced by drought in both species. Reliability of expression patterns has been confirmed by RT-PCR. While induced genes with similar profiles in both species can be considered as general candidate genes for the study of drought response in conifers, genes with diverging expression patterns can underpin the differences displayed by these species under water stress. Most promising candidate genes for drought stress response include genes related to carbohydrate metabolism, such as glycosyltransferases or galactosidases, sugar transporters, dehydrins and transcription factors. Additionally, differences in the molecular response to drought and polyethylene-glycol-induced water stress are also discussed.
The use of solar energy in photosynthesis depends on the ability to safely dissipate excess energy. The key dissipation process employed by plants in their natural environment is mediated by a particular group of carotenoids. Multiple levels of control allow adjustments in energy dissipation activity in response to changing levels of light stress in the natural environment. Recent advances in the understanding of the photophysics, biochemical regulation and ecophysiology of this essential photoprotective process are reviewed.
We exposed seedlings of Cotinus coggygria var. cinerea to drought and exogenous abscisic acid (ABA) under two different light conditions. Two watering regimes (well-watered and drought), two exogenous ABA applications (no ABA and with ABA) and two light regimes (full sunlight and shade) were employed. Compared with well-watered treatment, drought treatment significantly reduced the relative growth rate, relative water content (RWC), net photosynthesis rate (A) and transpiration (E), but increased chlorophyll a (chla), carbon isotope (δ13C), endogenous ABA, malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents, and guaiacol peroxidase (POD) and catalase (CAT) activities. There was an apparent alleviation of drought effects by shade, as indicated by the lower relative growth rate, and chlorophyll, MDA and H2O2 contents, and increases in indoleacetic acid (IAA) and reduced glutathione (GSH) contents. On the other hand, the exogenous ABA application under shade induced protective effects on drought-stressed seedlings, as visible in RWC, MDA, A, stomatal conductance (gs), E, δ13C, ABA and IAA values. In all, our results suggest that seedlings of C. coggygria are more sensitive to drought under full-light than under shade.
Changes in amount of the plant alkaloid, camptothecin (CPT), were investigated in field-grown Camptotheca acuminata seedlings in response to fertilization, variation in plant density, and cokppicing. The relationship between CPT and growth, and abscisic acid (ABA) levels were also examined. Fertilization caused positive responses in growth of both the slow- and the fast-growing C. acuminata plants. It lowered stomatal conductance (g), reduced leaf CPT level in slow-growing but not fast-growing seedlings in mid-summer (July), and increased leaf ABA level in dense plantings in early fall (September). Shoots induced to develop as a result of cokppicing were significantly higher in leaf CPT level than the original non-cokppiced shoots. These results suggest that in the C. acuminata plantation management, cokppicing should be employed to produce high concentrations of CPT, but that soil fertilization should be used cautiously so that greater growth is not achieved at the cost of lower CPT biosynthesis.