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The effects of drought and rehydration on tea seedlings were significant. After five days of drought imposition the contents of chlorophylls, carotenoids, ascorbate and glutathione, and activities of guaiacol peroxidase and glutathione reductase decreased. Simultaneously, contents of proline, H2O2 and superoxide anion, lipid peroxidation and activities of catalase and superoxide dismutase increased. These parameters recovered to different degrees during subsequent rehydration.
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BIOLOGIA PLANTARUM 48 (4): 597-600, 2004
Responses of Camellia sinensis to drought and rehydration
Plant Biochemistry Laboratory, Department of Life Science, Assam (Central) University, Silchar-788011, India*
Research Institute for Bioresources, Okayama University, Kurashiki-7100046, Japan**
The effects of drought and rehydration on tea seedlings were significant. After five days of drought imposition the
contents of chlorophylls, carotenoids, ascorbate and glutathione, and activities of guaiacol peroxidase and glutathione
reductase decreased. Simultaneously, contents of proline, H2O2 and superoxide anion, lipid peroxidation and activities of
catalase and superoxide dismutase increased. These parameters recovered to different degrees during subsequent
Additional key words: ascorbate, carotenoid, catalase, chlorophyll, glutathione, guaiacol peroxidase, superoxide anion, superoxide
Tea plant being perennial shrubs can grow under diverse
climatic conditions and is always subjected to
environmental stress. Plant may suffer either from
excessive soil moisture or moisture deficit. Drought being
an important limitation for plant impairs severely growth,
crop yield and various morphological, anatomical,
physiological and biochemical processes (Kefei et al.
1997, Egert and Tevini 2002). The drought resistance
mechanisms can be categorised as 1) drought avoidence,
2) dehydration tolerance, and 3) dehydration postpone-
ment (Kramer and Boyer 1995). Plant may perceive
osmotic adjustment as a survival mechanism, which
enable physiological activity to be maintained at a lower
level throughout a period of water deficit (Turner 1997).
Drought tolerance mechanisms have been compared in
the clones of different plant species (e.g. in Coffea
canephora; DaMatta et. al. 2003). The post drought
recovery by the plant is also a subject of much concern.
Drought is known to cause oxidative damage in plants
as a result of production of reactive oxygen species
(ROS) like, superoxide radical, hydroxyl radical,
hydroperoxide radical, alkoxyl radical, and hydrogen
peroxide, which are inevitable products of natural redox
reactions occurring in various cellular compartments
(Zhang and Kirkham 1994, Alscher et al. 1997, Panda
2002). However, plants possess both enzymic
>superoxide dismutase (SOD), catalase (CAT), ascorbate
peroxidase (APX) guiacol peroxidase (GPX), and
glutathione reductase (GR)@ and non enzymic (carote-
noids, ascorbate, glutathione, D-tocopherol) antioxidants
to overcome the toxic effect of ROS.
The level of osmolytes or osmoprotectants are
increased in plant subjected to drought. Increase in total
free amino acids and free proline were reported in wheat
(Levitt 1980, Kathju et al. 1988) and in tea (Handique
and Manivel 1990), respectively. The molecular
mechanism of quenching of ROS by proline under
stresses, which includes water stress is well reviewed by
Matysik et al. (2002). Besides the contents and compo-
sition of osmolytes the antioxidant property also varies
between the drought susceptible and drought resistant
plants. The present experiment was undertaken to
understand the drought imposed damage and its recovery
in the developing clonal tea plant like other crop plant.
Healthy and uniform 1-year-old clonal seedlings of
tea [Camellia sinensis (L.) O. Kuntze] were procured from
Tocklai Tea Research station, Silchar, and grown under a
natural light in a greenhouse. Drought was induced by
Received 19 September 2003, accepted 12 May 2004.
Abbreviations: APX - ascorbate peroxidase; CAT - catalase; GPX - guaiacol peroxidase; GR - glutathione reductase; PDR - post-
drought rehydration; ROS - reactive oxygen species; RWC - relative water content; SOD - superoxide dismutase;
TBA - thiobarbituric acid; TBARS - thiobarbituric acid reactive substance; TCA - trichloroacetic acid.
1 Corresponding author, fax: (+81) 86 434 1210, e-mail:
withholding the watering for five days under controlled
conditions. On the sixth day leaves from the control and
drought imposed tea seedlings were sampled for various
biochemical analysis and plants were rehydrated for
another five days. On the sixth day of rehydration leaves
were again sampled.
Leaves were extracted in cold 80 % acetone and
chlorophylls and carotenoids were extracted and
estimated by spectrophotometer type 106, (Systronics,
India) as per the methods of Arnon (1949). Extraction
and estimation of H2O2 content was done according to
Sagisaka (1976). Lipid peroxidation was measured as the
amount of thiobarbituric acid reactive substance
(TBARS) determined by the thiobarbituric acid (TBA)
reaction as described by Heath and Packer (1968).
Glutathione was extracted and estimated according to
Griffith (1980). For the extraction and estimation of
ascorbate method of Oser (1979) was used. Proline
content in leaves was determined following the method of
Bates et al. (1973). Presence of superoxide anion (O2˙Ǧ)
was determined as described by Elstner and Heupel
(1976). Relative water content (RWC), defined as water
content of tissue as a percentage of that in water saturated
leaf tissue, was determined by the method of Weatherley
(1950). Samples of fresh tissue were floated in distilled
water at 25 r 1 qC for 4 h.
The leaf tissues were homogenised with phosphate
buffer pH 6.8 (0.1M) in prechilled mortar and pestle. The
extract was centrifuged at 4 qC for 15 min at 17 000 g in
a cooling centrifuge. The supernatant was used for the
assay of CAT, GPX, SOD, and GR. Extractions and
assay of CAT, GPX, GR, and SOD were done as per the
methods described in Chance and Maehly (1955),
Fig. 1. Changes in contents of proline, H2O2, thiobarbituric aci
reactive substances (TBARS) (A), ascorbate (Asc), glutathione
(Glu) and superoxide anion (SA) (B) in Camellia sinensis
leaves subjected to drought stress and rehydration (PDR).
Means of 5 separate experiments r SE.
Giannopolitis and Reis (1977) and Smith et al. (1988)
respectively. Each experiment was repeated five times
and data presented are means r SE.
RWC decreased with drought stress, but only a slight
increase in RWC was observed on rehydration for 5 d. A
decrease in chlorophyll (Chl) and carotenoid (Car)
contents (42 and 51.96 % of that in control plants,
respectively) was observed after 5 d of drought treatment.
Such observation suggested a drought induced pigment
degradations (Baisak et. al. 1994) and/or inhibition of
their synthesis. Decrease in net photosynthetic rate by
water stress in tea seedlings was observed by Sobrado
(1996) and Yordanov et al. (2000). After rehydration, Chl
and Car contents were 34.18 and 7.25 %, respectively,
less than those in the control.
Fig. 2. Changes in chlorophyll (Chl) and carotenoid (Car)
contents (A), and superoxide dismutase (SOD), catalase (CAT),
guaiacol peroxidase (GPX) and glutahione reductase (GR)
activities (B), and relative water content (RWC) (C) in
Camellia sinensis leaves subjected to drought stress an
rehydration (PDR). Means r SE, n = 5.
An increase in proline content (251.64 %) was
observed, whereas after rehydration it decreased to
108.07 % of that in control. Such proline accumulation in
response to water deficit stress was reported in wheat
(Kathju et al. 1988, Levitt 1980) and in tea (Handique
and Manivel 1990). However, this accumulation may not
be sufficient to reduce completely the damaging effect of
dehydration on membrane disintegration or enzyme
inactivation (Bohnert and Jenson 1996).
TBARS content is the measure of lipid peroxidation.
It significantly increased in drought treated plants, but
rehydration showed decrease of the same. An increase in
H2O2 content with simultaneous increase in lipid
peroxidation in drought imposed tea plant suggested a
loss of membrane function and induction of oxidative
damage (Zhang and Kirkham 1994, Baisak et al. 1994,
Sairam et al. 1997, Fu and Huang 2001, Egert and Tevini
2002). But post drought recovery analysis suggested that
rehydration minimizes the negative effect of drought, as
was evidenced by 44.57 % decreased lipid peroxidation
and 7.8 % decrease in H2O2 content observed after
rewatering the drought imposed plant.
Although an increase in SOD activity was visible with
simultaneous increase in CAT activity, significant
decrease in GPX and GR activities and a decrease in
contents of non-enzymic antioxidants, ascorbate and
glutathione suggested the incomplete ability of tea
seedlings to overcome a drought induced oxidative stress.
This is in agreement with results of Mukherjee and
Choudhuri (1983), Jagtap and Bhargava (1995), Egert
and Tevini (2002), and Fu and Huang (2001). The post
drought recovery analysis suggested a marked increase in
GPX, GR and CAT activities after rehydration of drought
imposed tea seedlings with significant decrease in SOD
activity. The increased amount of superoxide anion in
drought imposed tea seedlings and its little recovery on
subsequent rehydration also confirmed oxidative stress
In conclusion, imposition of drought caused serious
damage in tea seedlings and only moderate recovery was
noticed upon rehydration.
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... Drought is a major environmental constraint reducing the yield of many economically important crops, and climate aridization has been increasing worldwide. One negative effect of drought stress is oxidative damage leading to disturbances of physiological and biochemical processes causing significant losses in tea quality and yields (Upadhyaya & Panda, 2004;Marci nska et al., 2013;Maritim et al., 2015). During earlier research, many genetic and physiological mechanisms of drought tolerance have been clarified in various crops including the tea crop (Bhagat, Baruah & Cacigue, 2010;Damayanthi, Mohotti1 & Nissanka, 2010;Man et al., 2011;Baruah & Bhagat, 2012;Maritim et al., 2015;Zhu, 2016;Fleta-Soriano & Munné-Bosch, 2016;Malyukova et al., 2020Malyukova et al., , 2021Samarina et al., 2020). ...
... Although many mechanisms of tea drought responses have been revealed, the topic of exogenous regulation of drought tolerance by chemical and biological compounds is still not elucidated sufficiently. Some studies indicate enhancement of drought tolerance by hormone treatments (Man et al., 2011;Njoloma, 2012;Upadhyaya & Panda, 2004). On the other hand, external application of mineral nutrients to increase drought tolerance still has not been studied well. ...
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Background Drought is one of the major factors reducing the yield of many crops worldwide, including the tea crop ( Camellia sinensis (L.) Kuntze). Calcium participates in most of cellular signaling processes, and its important role in stress detection and triggering a response has been shown in many crops. The aim of this study was to evaluate possible effects of calcium on the tea plant response to drought. Methods Experiments were conducted using 3-year-old potted tea plants of the best local cultivar Kolkhida. Application of ammonium nitrate (control treatment) or calcium nitrate (Ca treatment) to the soil was performed before drought induction. Next, a 7-day drought was induced in both groups of plants. The following physiological parameters were measured: relative electrical conductivity, pH of cell sap, and concentrations of cations, sugars, and amino acids. In addition, relative expression levels of 40 stress-related and crop quality–related genes were analyzed. Results Under drought stress, leaf electrolyte leakage differed significantly, indicating greater damage to cell membranes in control plants than in Ca-treated plants. Calcium application resulted in greater pH of cell sap; higher accumulation of tyrosine, methionine, and valine; and a greater Mg ²⁺ content as compared to control plants. Drought stress downregulated most of the quality-related genes in both groups of tea plants. By contrast, significant upregulation of some genes was observed, namely CRK45 , NAC26 , TPS11 , LOX1 , LOX6 , Hydrolase22 , DREB26 , SWEET2 , GS , ADC , DHN2 , GOLS1 , GOLS3 , and RHL41 . Among them, three genes ( LOX1 , RHL41 , and GOLS1 ) showed 2–3 times greater expression in Ca-treated plants than in control plants. Based on these results, it can be speculated that calcium affects galactinol biosynthesis and participates in the regulation of stomatal aperture not only through activation of abscisic-acid signaling but also through jasmonic-acid pathway activation. These findings clarify calcium-mediated mechanisms of drought defense in tree crops. Thus, calcium improves the drought response in the tea tree.
... A study on tea plants revealed that under drought stress, the expression of the genes related to flavonoid biosynthesis, including CHS, dihydrofavonol 4-reductase (DFR), Leucoanthocyanidin reductase (LAR), and leucoanthocyanidin dioxygenase (ANS), was decreased in the early stages of the drought but subsequently increased by continuous drought stress [108]. The significant upregulation of flavonoid biosynthesis genes (phenylalanine ammonia-lyase (PAL), cinnamic acid 4-hydroxylase (C4H), 4-coumarateCoA ligase (4CL), CHS, and Dihydrofavonol 4-reductase (DFR)) was demonstrated by another study on tea plant under drought condition [85]. ...
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Flavonoids are characterized as the low molecular weight polyphenolic compounds universally distributed in planta. They are a chemically varied group of secondary metabolites with a broad range of biological activity. The increasing amount of evidence has demonstrated the various physiological functions of flavonoids in stress response. In this paper, we provide a brief introduction to flavonoids’ biochemistry and biosynthesis. Then, we review the recent findings on the alternation of flavonoid content under different stress conditions to come up with an overall picture of the mechanism of involvement of flavonoids in plants’ response to various abiotic stresses. The participation of flavonoids in antioxidant systems, flavonoid-mediated response to different abiotic stresses, the involvement of flavonoids in stress signaling networks, and the physiological response of plants under stress conditions are discussed in this review. Moreover, molecular and genetic approaches to tailoring flavonoid biosynthesis and regulation under abiotic stress are addressed in this review.
... Previous studies have shown that leaf RWC of Caragana korshinskii Kom declined sharply under extreme drought, eventually leading to leaf abscission (Xu et al., 2012). Moreover, plants subjected to drought stress generally had lower RWC than the control and recovered somewhat after rehydration (Upadhyaya and Panda, 2004;Benetti Mantoan et al., 2016), which is consistent with our findings for A. selengensis. These results indicate that RWC of A. selengensis can not only be maintained at a high level under drought conditions but also recover quickly after rehydration under SD and MD. ...
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Changes in global climate and precipitation patterns have exacerbated the existing uneven distribution of water, causing many plants to face the alternate situation of drought and water flooding. We studied the growth and physiological response of the wetland plant Artemisia selengensis to drought and rehydration. In this study, Artemisia selengensis seedlings were subjected to 32.89% (SD), 47.36 % (MD), 60.97% (MID), and 87.18 % (CK) field water holding capacity for 70 days, followed by 14 days of rehydration. The results showed that drought inhibited the increase of plant height, basal diameter, and biomass accumulation under SD and MD, but the root shoot ratio (R/S) increased. Drought stress also decreased the content of total chlorophyll (Chl), chlorophyll a (Chl-a), chlorophyll b (Chl-b), and carotenoid (Car). Soluble sugar (SS) and proline (Pro) were accumulated rapidly under drought, and the relative water content (RWC) of leaves was kept at a high level of 80%. After rehydration, the plant height, basal diameter, biomass, and R/S ratio could not be recovered under SD and MD, but these indicators were completely recovered under MID. The RWC, Chl, Chl-a, Chl-b, Car, and osmotic substances were partially or completely recovered. In conclusion, Artemisia selengensis not only can improve drought resistance by increasing the R/S ratio and osmotic substances but also adopt the compensatory mechanism during rehydration. It is predictable that A. selengensis may benefit from possible future aridification of wetlands and expand population distribution.
... As a product of membrane lipid peroxidation, the content of malondialdehyde (MDA) can reflect the degree of damage to the cell membrane. The decrease in hydrogen peroxide (H 2 O 2 ) and content of MDA during the post-drought recovery of tea seedlings indicated that rehydration reduced the negative effects of drought stress (Upadhyaya and Panda, 2004). ...
The mustard variety Felicia was used to analyze the response and compensation effects of growth and physiology under drought stress and rehydration conditions at the seedling stage. The seedlings were exposed to different levels of drought stress simulated by polyethylene glycol (PEG). The growth parameters, fresh weight, chlorophyll fluorescence, and antioxidant system were measured. The results showed that drought stress inhibited the growth of roots and shoots and reduced the performance of photosystem II (PS II). After rehydration, the root length and fresh weight of plants rapidly increased, and the performance index (PIABS) was found to be higher compared with the control, which suggested a compensative effect. The chlorophyll content was significantly reduced under moderate and severe drought stress. However, it increased under mild stress conditions. After rehydration, the chlorophyll content under moderate and severe stress did not return to the levels of control, and there was no significant difference between mild stress and the control. Under drought stress, the activities of antioxidant enzymes and content of malondialdehyde (MDA) increased significantly in the leaves. After rehydration, MDA and the activities of antioxidant enzyme were higher than those of the control group, particularly under moderate and severe stress. Therefore, these results suggest that mustard is strongly adapted to mild drought stress through the efficient activities of antioxidant enzymes activity and photosynthesis, as well as its rapid recovery after rehydration.
... Plants are equipped with an antioxidant defense system against the damaging effects of reactive oxygen species which consists of two groups of enzymatic (ascorbate peroxidase, catalase, superoxide dismutase, glutathione reductase, guaiac peroxidase, and others) and non-enzymatic antioxidants (carotenoids, ascorbates, glutathione, vitamin E, and others) [44]. The metabolism of antioxidants is one of the pathways of plant metabolism that can affect abiotic stress tolerance. ...
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Background Abiotic and biotic stresses induce oxidative processes in plant cells that this process starts with the production of ROSs which cause damage to the proteins. Therefore, plants have increased their antioxidant activity to defend against this oxidative stress to be able to handle stress better. In this research, 14 different tea accessions in a randomized complete block design with two replications were evaluated in two normal and drought stress conditions, and their antioxidant activity was measured by DPPH-free radicals’ assay and gene expression analysis. Results The results of gene expression analysis showed that the 100 and 399 accessions and Bazri cultivar had high values for most of the antioxidant enzymes, ascorbate peroxidase, superoxide dismutase, catalase, and peroxidase under drought stress conditions while the 278 and 276 accessions had the lowest amount of antioxidant enzymes in the same situation. Results showed that the IC50 of the BHT combination was 90.12 μg/ ml. Also, The IC50 of accessions ranged from 218 to 261 μg/ml and 201–264 μg/ml at normal and drought stress conditions, respectively. The 100 and 399 accessions showed the lowest IC50 under normal and drought stress conditions, while 278 and 276 accessions had the highest value for IC50. The antioxidant activity of tea accession extracts under normal conditions was ranged from 25 to 69% for accessions 278 and 100, respectively. While, the antioxidant activities of extracts under drought stress condition was 12 to 83% for accessions 276 and 100, respectively. So, according to the results, 100 and 399 accessions exhibited the least IC50 and more antioxidant activity under drought stress conditions and were identified as stress-tolerant accessions. However, 278 and 276 accessions did not show much antioxidant activity and were recognized as sensitive accessions under drought stress conditions. Conclusions These results demonstrate that total phenol content, antioxidant activity, and the oxygen-scavenging system can be used as a descriptor for identifying drought-tolerant accessions.
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Germination and seedling establishment are sensitive and important stages in the life cycle of plants that are affected by abiotic stresses, especially drought and salinity stresses. This study was conducted to investigate the effects of osmotic potential (due to sodium chloride and polyethylene glycol) on germination and biochemical indices of Salicornia sinus-persica Akhani spec. nov.Akhani seeds in 2020 in the Agriculture Laboratory of Yasouj University of Agriculture in a completely randomized design with three replications of 50 seeds. A separate experiment was performed in which the first experiment consisted of 13 levels of osmotic potential (zero, -0.3, -0.6, -0.9, -1.2, -1.5, -1.8, -1.2, -2.4, -2.7, -3, -3.3 and -3.6 MPa) which were made of polyethylene glycol and the second experiment included 13 salinity stress levels with osmosis similar to the first experiment (zero, 62, 122, 187, 249, 311, 368, 435, 498, 560, 622, 684 and 746 mM) were used to make sodium chloride. The results showed that the trend of salicornia seed germination indices in salinity and drought stresses had a constant trend up to the level of about -1.2 (249 mM) and -0.6 MPa, respectively, and then with a decrease in the osmotic potential of germination percentage, root and stem length, root and shoot dry weight and seedling vigor length and weight index showed a decreasing trend so that the slope of this decreasing trend was higher in drought stress compared with salinity stress. From osmotic potential of 1.2 MPa onwards, in salinity thirst, seed biochemical parameters such as proline content, malondialdehyde content and sodium element increased whereas potassium element decreased and in drought stress, proline and malondialdehyde content showed an increasing trend. In general, Salicornia seeds were more sensitive to drought stress than salinity stress.
Drought stress really restring the growth and development of tea plant and affecting quality and yield. In tea growing areas of Iran, drought stress is a serious problem that affects the yield and quality of green leaves, therefore introducing cultivars that tolerate drought stress is one of the breeding purpose. To distinguish the variations in four tea cultivars response to drought stress and the role of melatonin in reducing the destructive effects of drought stress, an experiment was done at Tea Research Center of Iran, using the factorial based on completely randomized design with three replicates. The first experimental factor was the cultivar at 4 levels (DG39, DG7, DN and Kashef) and the second factor was irrigation interruption treatment at 5 levels, including control (full irrigation), irrigation interruption for 7 days with 100 µm melatonin foliar application, irrigation interruption for 7 days without melatonin foliar application, irrigation interruption for 14 days with melatonin foliar application and irrigation interruption for 14 days without melatonin foliar application. The study indicated that the physiological and biochemical traits were significantly different among the cultivars and treatments. Based on some traits such as malondialdehyde, the activities of antioxidant enzymes (CAT, POD), carotenoid and polyphenol content, DG 39 and based on traits such as proline, total sugar and chlorophyll content, DN are introduced as the cultivars that showed better tolerance to drought stress and these cultivars can be used in future breeding programs. Also melatonin treatment significantly enhanced the drought tolerance of tea seedlings, as demonstrated by decreased membrane damage, raised the concentration of proline, total protein, and total sugar and enhanced the activities of catalase and peroxidase during drought stress.
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نوسانات فصلی و آب و هوایی تحت تأثیر عواملی مانند بارندگی، درجهی حرارت، رطوبت نسبی و کمبود آب در خاك قرار میگیرند که خود بر توزیع و میزان عملکرد و کیفیت چای و تولید اقتصادی آن، تأثیرگذار هستند. تنش کمبود آب یکی از انواع تنشهای غیرزنده در گیاهان است،که سبب کاهش تولید و عملکرد محصولات کشاورزی در جهان میگردد. زمانی که گیاهان تحت تنش کمبود آب قرار میگیرند، پاسخهای فیزیولوژیکی، مورفولوژیکی و بیوشیمیایی مختلفی را از خود نشان میدهند
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The experiment was conducted in the wooden canopy in the botanical garden of Biology Department , College of Education for pure science – Ibn AL – Haitham , Baghdad University using clay pots to investigate the effect of foliar spraying with Gibberellic acid in three concentrations (0 ,50 and 100) mg. L ¹ and three concentrations of Proline acid(0, 25 and 50)mg. L ¹ and their interactions on some vegetative growth as (the content of nitrogen ,phosphorous, calcium and total chlorophyll) and some yield components as ( the lentght of pods , no. of pods . plant ¹ , no. of seeds . Plant ¹ , wt . of seeds . plant ¹ )and the percentage of protein of the seeds of pea plant . The experiment was designed according to Completely Randomized Design(CRD) with three replications. Results indicated that, foliar spraying with Gibberellic and Proline acid caused a significant increase in all growth parameters , and the interaction caused a significant effect where the concentration 100 mg. L ¹ Gibberellic acid and the concentration 50 mg. L ¹ Proline acid gave the best values for the content of the elements , the length of pods . no. of pods . plant ¹ but the concentration 50mg. L ¹ Gibberellic acid and the concentration 50mg. L ¹ Proline acid gave the best value for the content of total chlorophyll on the other hand, the treatment 50mg. L ¹ Gibberellic acid and 25 mg. L ¹ Proline acid gave the highest values for wt. of seeds . plant ¹ , the best value for the seeds protein was in the concentration 100 mg. L ¹ Gibberellic acid and the concentration 25 mg. L ¹ Proline acid.
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Introduction: Tea plant (Camellia sinensis L.) has great potential for growth in acidic soils and is adapted to soil and a climatic condition of Guilan province. Tea requires acidic conditions, high heat and high humidity, and its leaves are economically important (Taiefeh et al., 2013). Various studies have shown that the yield of green tea leaves and its physiological and biochemical properties depend on factors such as soil type, altitude, season, climatic conditions, and the amount of water available to the plant and the consumption of macro and micro elements (Owuor and Bowa, 2012). One of the prominent issues in the production of crops and orchards, including tea orchards, is strengthening their resistance to dry conditions, and among them, water deficit stress is the most common type of environmental stress that affects plant growth and production (Kirigwi et al., 2004). The element copper is very important in the growth and production of quality tea, so that by interfering with the oxidation of green tea leaves, it directly affects the taste and color of tea (Singh and Singh, 2004). Zinc as a major factor in the activity of many enzymes and play a major role in the structure of proteins that regulate transcription in leaves of tea plays, therefore, reducing the concentration of this element reduces the stomatal conductance, reduces transpiration and degrades the function of antioxidant enzymes (Upadhyaya et al., 2013). This study was conducted to investigate the effect of application of copper and zinc nano-fertilizers and irrigation water deficiency on different morpho-physiological and biochemical characteristics of tea plant in garden conditions. Materials and Methods: This research was carried out as a factorial experiment in a randomized complete block design with three replications in selected tea research gardens of Rudsar city in 2018. Factorial combinations of three treatments of water deficit stress (15% (un-stressed control, IR1), 30% (moderate stress, IR2) and 45% (severe stress, IR3) of FC depletion) and four foliar application (FA1: use distil water, control, FA2: Copper nano-chelate (0.5 mg per one liter of distilled water), FA3: Zinc nano-chelate (2.5 mg per one liter of distilled water) and FA4: Copper nano-chelate + Zinc nano-chelate) were considered. The applied drought stress levels were determined between the field capacity and the permanent wilting point of the soil in the tested area to determine the plant response to different soil water levels (Mokhtassi-Bidgoli et al., 2013). The amount of chemical fertilizers required was determined based on the results of soil test (Table 1) and the amount of nutrients harvested by tea plants (Table 2) (Sedaghathoor et al., 2003). Results and Discussion: The results of this study showed that the interaction of irrigation regimes and foliar application on green leaf yield, photosynthesis rate, proline concentration, catalase, peroxidase and superoxide dismutase activity were significant. Under moderate stress conditions, optimal green leaf yield and plant photosynthesis rate were obtained from the combined foliar application of copper and zinc nano-fertilizers. Also, under severe stress conditions, the highest amount of antioxidant activity and proline concentration was observed in the combined spraying of copper and zinc nano-fertilizers. Total chlorophyll decreased fewer than 62.5 and 75 % under moderate and severe stress conditions compared to the control treatment. Also, carotenoids under the influence of copper foliar application, zinc foliar application and combined copper and zinc foliar application increased by 38.47, 43.84 and 69.29% compared to the control treatment. Conclusions: In general, it can be concluded that the application of combined foliar application of copper and zinc increased 58.40, 32.54 and 31.28% of green tea leaf yield compared to the control under moderate stress conditions, respectively. The results proved copper and zinc micronutrients increase green leaf yield, photosynthetic rate, photosynthetic pigments, soluble carbohydrate and protein concentrations, as well as increase the activity of antioxidants in stress conditions. Also, results showed that zinc and copper are very effective in tea resistance to water stress and reduction of dehydration damage.
A photo-induced cyclic peroxidation in isolated chloroplasts is described. In an osmotic buffered medium, chloroplasts upon illumination produce malondialdehyde (MDA)—a decomposition product of tri-unsaturated fatty acid hydroperoxides—bleach endogenous chlorophyll, and consume oxygen. These processes show (a) no reaction in the absence of illumination; (b) an initial lag phase upon illumination of 10-20 minutes duration; (c) a linear phase in which the rate is proportional to the square root of the light intensity; (d) cessation of reaction occurring within 3 minutes after illumination ceases; and (e) a termination phase after several hours of illumination. The kinetics of the above processes fit a cyclic peroxidation equation with velocity coefficients near those for chemical peroxidation. The stoichiometry of MDA/O2 = 0.02, and O2/Chlbleached = 6.9 correlates well with MDA production efficiency in other biological systems and with the molar ratio of unsaturated fatty acids to chlorophyll. The energies of activation for the lag and linear phases are 17 and 0 kcal/mole, respectively, the same as that for autoxidation. During the linear phase of oxygen uptake the dependence upon temperature and O2 concentration indicates that during the reaction, oxygen tension at the site of peroxidation is 100-fold lower than in the aqueous phase. It is concluded that isolated chloroplasts upon illumination can undergo a cyclic peroxidation initiated by the light absorbed by chlorophyll. Photoperoxidation results in a destruction of the chlorophyll and tri-unsaturated fatty acids of the chloroplast membranes.
In five leaf age classes of an evergreen tree Curatella americana L. widespread in savanna, fluorescence parameters, water loss and carbon assimilation were measured during both wet and dry seasons, and afterwards their nitrogen and water use efficiencies were analyzed. Variable to maximum fluorescence ratios (F(v)/F(m) ≃ 0.74) were higher in mature leaves than in expanding (≃ 0.68) and senescing ones (≃ 0.66). Lower F(v)/F(m) in these leaf stages did not seem to be caused by photoinhibition but by a low photochemical capacity as suggested by chlorophyll a/b ratios. Moreover, these results did not change with drought, which indicated the absence of photoinhibition for all leaf stages. Maximum net photosynthetic rates (P(max)) of about 9.5 mmol m-2 s-1 were observed in mature leaves during humid season. Expanding and old leaves had lower P(max). With drought onset P(max), stomatal conductance and water loss were reduced.
The effects of water stress on the alterations in the activities of active oxygen scavenging enzymes of primary wheat leaves were studied by incubating the leaf segments with different concentrations of polyethylene glycol solutions. Water stress caused a faster decline in the chlorophyll and protein contents and an increase in the level of proline relative to the controls. Catalase activity initially increased with time and then declined in the control leaf segments and imposition of water stress prevented the increase to different degrees depending upon the degree of stress. Water stress also caused a rapid increase in the activity of superoxide dismutase (SOD). Ascorbate peroxidase (APOX) activitiy increased in the leaves subjected to mild water stress but declined during severe water stress while glutathione reductase (GR) activity increased under all water stress conditions studied here as compared to the control. Lipid peroxidation was enhanced under severe water stress conditions but not under mild water stress. The changes in the different parameters followed in this study, thus, are dependent upon the degree of water stress. The increases in the activities of SOD and GR in response to water stress are probably due to the de novo synthesis of enzymatic proteins. Decline in the efficacy of the H2O2 decomposing system is probably responsible for the oxidative damage occurring in water stressed leaves.
The imposition of oxidative stress lends to increased production of reactive oxygen species (ROS) in plant cells. Orchestrated defense processes ensue that have much in common between stresses, yet are also particular to the site of action of the stress and its concentration. Possible functional roles of these responses include, but me not restricted to, the protection of the photosynthetic machinery, the preservation of membrane integrity and the protection of DNA and proteins. Superimposed upon our understanding of cellular mechanisms for protection against abiotic stress is a newly discovered role of ROS in signalling and defense response to pathogens (J. L. Dangl, R. A. Dietrich and M. S. Richherg. 1996. Plant Cell 8: 1793-1807). Evidence to date suggests a coordinated response to ROS among different members of the superoxide dismutase (SOD) gene families. A further layer of complexity is afforded by reports of coordination of expression between ascorbate peroxidase and SOD genes, Our understanding of the signalling mechanisms that underlie these coordinated events is in its infancy. An exciting future lies ahead in which the orchestration of successful antioxidant stress responses will be gradually revealed. Current data suggest that complex regulatory mechanisms function at both the gene and protein level to coordinate antioxidant responses and that a critical role is played by organellar localization and inter-compartment coordination.