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The metal accumulation potential and its tolerance in the plants of Brassica juncea (L.) Czern. (cv. Rohini) grown on various amendments of tannery sludge (10%, 25%, 35%, 50%, 75%, 100%) were studied after 30, 60, and 90 days after sowing. These plants were found to be effective accumulators of metals (Cr, Fe, Zn, and Mn); however, the seeds accumulated the least quantities of all the metals tested. The oil content of the seeds was found to increase up to 35% tannery sludge followed by a decrease. An increase in the photosynthetic pigments, protein, and sugar contents was recorded at the lower amendments of tannery sludge at initial exposure periods followed by a decrease compared to their respective controls. However, the malondialdehyde, proline, and ascorbic acid contents of the roots and leaves of the plant increased at all the sludge amendments and exposure periods, compared to their respective controls. The levels of cysteine and nonprotein thiol contents in the roots and leaves of the treated plant were found higher at all the sludge amendments and exposure periods except at 90 days, where a decrease was observed in the leaves at 100% tannery sludge as compared to their respective controls. The tolerance exhibited by the sludge-grown plants of B. juncea in the present study may be attributed to the enhanced level of the antioxidants induced under stress conditions. r 2005 Elsevier Inc. All rights reserved.
The present investigation was designed to analyze the influence of Helium-Neon (He-Ne- 632.8 nm) laser irradiation on defense enzymes, proline content and in vitro responses of callus induction, shoot initiation and on plantlet regeneration potential of brinjal. The seeds of Mattu Gulla (Solanum melongena L.) were irradiated with 20, 25 and 30 J/cm2 of He-Ne laser irradiation followed by surface sterilization and sprouted on Murashige and Skoog medium without plant growth regulators. The activity of defense enzymes, proline content and the organogenetic potential of hypocotyl, leaf and shoot tip explants were determined from thirty day old seedlings. During seed germination, most of the seedlings showed normal two cotyledons whereas small number of seedlings showed tricotyledonous at 20 J/cm2 treatment and no other morphological abnormalities were observed during further growth and development. There was no substantial variation was noted in both β-1,3-glucanase and chitinase activity as well as proline content which proves the He-Ne laser irradiation does not causes any stresses for the plant. The in vitro culture of hypocotyl, leaf and shoot tip explants from laser irradiated seedlings showed differential responses as compared to un-irradiated control. The laser induced enhancement of callus induction, growth rate of callus tissues and shoot tip, percentage of responses of shoot and root initiation, days to shoot and root initiation, shoots formed per callus, number of roots per shoots, length of roots and nuclear DNA content of in vitro raised plants were evaluated. Among the tested laser doses (20, 25 and 30 J/cm2), 25 J/cm2 showed significant biostimulatory effect over un-irradiated control seedlings. The present observations reveal and endorsed our earlier reports with substantial enhancement of in vitro and ex vitro by He-Ne laser irradiation.
This study was conducted to examine the efficacy of Zn in correcting physiological responses of fennel to water deficit. Twelve field-grown fennel genotypes were subjected to two levels of irrigation (irrigation after 25-35% and 75-85% depletion of available soil water) and two levels of foliar-applied zinc (Zn) (0 and 4 g kg–1). Water deprivation left significant effects on all characteristics, i.e. in contrast to seed essential oil concentration, harvest index and super oxide dismutase and catalase activities, it led to decreases in the rest of the attributes. Varietal differences in response to drought were meaningful for most of the traits; i.e. genotypic variations for dry mass and grain yield were consistent with differences among the genotypes in leaf water potential, relative water content, proline, and chlorophyll concentrations. Zn led to significant increases in all physiological attributes, including activation of antioxidant defense responses manifested in ascorbate peroxidase and super oxide dismutase activities and carotenoids concentration. The Zn effect tended to be more notable on the drought-stricken fennel plants in a majority of the traits. From our findings, Zn could be considered as a micronutrient effective in ameliorating at least in part the stressful effects of water deficit on fennel.
Rapid industrialization and uncontrolled metal discharge into environment is a global concern for crop production. Metal tolerant bacterium isolated from chilli rhizosphere was identified as Pseudomonas aeruginosa by 16S rDNA sequence analysis. Pseudomonas aeruginosa tolerated high concentrations of Cu (1400 μg ml⁻¹), Cd (1000 μg ml⁻¹) and Cr (1000 μg ml⁻¹). Pseudomonas aeruginosa CPSB1 produced multiple plant growth promoting biomolecules in the presence and absence of metals. Strain CPSB1 solubilized P at 400 μg ml⁻¹ of Cd, Cr and Cu. The strain was positive for indole-3-acetic acid (IAA), siderophores, hydrogen cyanide (HCN), ammonia (NH3) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase when grown with/without metals. The phytotoxic effects on wheat increased with increasing Cd, Cr and Cu rates. The P. aeruginosa CPSB1 inoculated wheat in contrast had better growth and yields under Cu, Cd and Cr stress. The root dry biomass of inoculated plants was enhanced by 44, 28 and 48% at 2007 mg Cu kg⁻¹, 36 mg Cd kg⁻¹ and 204 mg Cr kg⁻¹, respectively. The bioinoculant enhanced number of spikes, grain and straw yields by 25, 17 and 12%, respectively. Pseudomonas aeruginosa CPSB1 significantly declined the levels of catalase (CAT), glutathione reductase (GR) and superoxide dismutase SOD), proline and malondialdehyde (MDA), and reduced metal uptake by wheat. The study demonstrated that P. aeruginosa CPSB1 possessed plant growth promoting potentials, showed metal tolerance capability and had ability to counteract deleterious metal impacts. Due to these, P. aeruginosa CPSB1 could be used as bioinoculant for enhancing wheat production even in metal contaminated soils.
High temperatures are already a current reality. If necessary attention is not given to plant nutrition, including magnesium nutrition, large losses in productivity can occur when plants are subjected to combinations of these heat and nutrient stresses. Thus, the goal of our work was to investigate the importance of adequate magnesium nutrition for an effective antioxidant response in coffee seedlings subjected to heat stress. As such, six-month-old Coffea arabica L. seedlings were transferred to plastic containers containing nutrient solutions with different concentrations of magnesium (Mg) and were cultivated at two different temperatures (25 or 35 °C). Fully expanded leaves and roots were evaluated at the beginning of the treatment and after 10, 20 and 30 days for the concentrations of magnesium, hydrogen peroxide, proline, ascorbate, malondialdehyde, protein and amino acids as well as the activities of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase. The variables analyzed were mainly altered by the combination of stresses. Mg deficiency and heat stress caused an increase in hydrogen peroxide concentration that was accompanied by an increase in antioxidant metabolism and by greater production of proline and ascorbate. Nevertheless, antioxidant metabolism and osmoprotectants were insufficient at removing excess ROS, resulting in increased lipid peroxidation and protein degradation. When subjected to heat stress, coffee seedlings under adequate Mg nutrition showed lower production of hydrogen peroxide and, consequently, poor lipid peroxidation and protein denaturation compared with seedlings deficient in Mg. Therefore, adequate Mg nutrition is essential for minimizing oxidative damage caused by heat stress in coffee seedlings.
Wheat is one of the major staple food of the world, which is badly affected by water deficit stress. To fulfill the dietary needs of increasing population with depleting water resources there is need to adopt technologies which result in sufficient crop yield with less water consumption. One of them is partial root zone drying (PRD). Keeping in view these conditions, a wire house experiment was conducted at University College of Agriculture and Environmental Sciences, The Islamia University Bahawalpur during 2015, to screen out the different wheat genotypes for PRD. Five approved local wheat cultivars (V1= Galaxy-2013, V2= Punjab-2011, V3 = Faisalabad-2008, V4 = Lasani-2008 and V5 = V.8200) and two irrigation levels (I1 = control irrigation and I2 = PRD irrigation) with completely randomized design having four replications were used in the experiment. Among the varieties Galaxy-2013 performed the best and attained maximum plant height, leaf area, stomatal conductance, photosynthesis, total sugars, proline contents and antioxidant enzymes activities and minimum values of all growth and physiological parameters were recorded in variety V.8200. For irrigation levels, higher values of growth, physiological and water related parameters were recorded in control treatment (I1) except leaf water potential, osmotic potential, total sugars and proline contents. However enzymes activities were higher under PRD treatment for all varieties. It was concluded that Galaxy-2013 was the most compatible and V.8200 was the most susceptible variety under PRD condition, respectively and more quality traits and enzymatic activities were recorded under PRD condition as compared to control treatment.
Presence of the toxic metalloid, “arsenic (As)” is ubiquitous in the environment especially in the soil and water. Its excess availability in the soil retards growth and metabolism of plants via (a) slowing down the cell division/elongation, (b) overproduction of reactive oxygen species (ROS), (c) modulation of antioxidant enzymes, and (d) alteration of DNA profile/genomic template stability (GTS). In the current study, diphenylene iodonium (DPI), 24-epibrassinolide (EBL) and proline (Pro) were used to analyze their roles in eliminating the adverse effects of As. Glycine max L. (variety JS 335) seeds were subjected to As (75 μM, Sodium arsenite was used as source of As), and in combination with DPI (10 μM), EBL (0.5 μM) or Pro (10 mM), for five consecutive days, and effects of these treatment combinations were analyzed on germination percentage, biomass, membrane stability, GTS and expressions of defensive genes. In addition, the levels of As, ROS, malondialdehyde, DNA content, oxidation, fragmentation, polymorphism, DNase activity, endogenous Pro and pyrroline-5-carboxylate synthetase activity were evaluated. The results indicated that the treatments of DPI, EBL or Pro are capable to alleviate detrimental effects of As, gauged from above variables, but with different magnitudes. Apropos As-stress mitigation, Pro was found to be the most effective under the confines of the study protocol. This study certainly provides new ideas for intensifying studies to unravel elusive central mechanism of amelioration involving use of DPI, EBL or Pro in plants with confirmed As-toxicity.
Keywords
24-Epibrassinolide; Antioxidant enzymes; Arsenic; Diphenylene iodonium; Oxidative stress; Reactive oxygen species; Proline
Chilling stress is one of the major abiotic stresses affecting chickpea productivity worldwide. This study evaluated the potential role of seed priming in improving resistance to chilling stress in chickpea (cv. Punjab, 2008). The priming treatments involved soaking seeds of chickpea cultivar Punjab 2008 in either water for 8 h (on-farm priming), aerated water (hydropriming) for 18 h, or CaCl2 solution (ψs −1.25 MPa; osmopriming) for 18 h. Primed and untreated seeds were grown either at 18/15 °C (control) or 13/10 °C (chilling stress). Chilling stress suppressed the growth of chickpea while seed priming mitigated the adverse effects of chilling stress by improving stand establishment, growth, water relations, photosynthesis, α-amylase activity, sugar metabolism, antioxidant enzyme activity, membrane stability, and leaf accumulation of proline, nitrogen, potassium and soluble phenolics. Seed priming also improved the performance of chickpea under optimal (control) conditions. The overall order of improvement in resistance to chilling by using seed priming was osmopriming > hydropriming > on-farm priming. Osmopriming improved seedling dry weight, specific leaf area, leaf CO2 net assimilation rate, maximal photochemical efficiency of PSII, α-amylase activity, trehalose content and leaf relative water content by 10, 22, 17, 20, 73, 48 and 7%, respectively, relative to the non-primed control under chilling stress. Under optimal temperature conditions, the corresponding values were 30, 32, 16, 10, 83, 75 and 5%, respectively. Sugar metabolism, especially trehalose content, was strongly linked with stand establishment, photosynthesis, antioxidant potential (under chilling stress) and plant biomass. Overall, seed priming improved chickpea performance under both optimal temperature conditions and chilling stress through better germination metabolism and the accumulation of trehalose, which protected from oxidative damage and helped to maintain carbon assimilation and seedling growth.
This study explores the effects of arbuscular mycorrhizal (AM) represented by Glomus spp. colonization on Saccharum spontaneum (L), a potential bioenergy grass subjected to drought stress under greenhouse conditions. The different treatments were: (1) watered control plants without AM association, (2) watered control plants with AM association, (3) drought stressed plants without AM association, (4) drought stressed plants. The AM association was established with Saccharum spontaneum (L) as evident from the increase in percentage of root infection and distribution frequency of vesicles. AM plants maintained a higher leaf osmotic potential and relative water content as compared to non-AM plants to counter osmotic stress in S. spontaneum. Accumulation of sugar (71 and 47% in AM and non-AM plants, respectively), proline (8.5 fold and 4 fold in AM and non-AM plants, respectively) and phenolic content (101 and 68% in AM and non-AM plants, respectively) were higher in AM plants as compared to non-AM plants on 12 d of imparting drought stress. Protein (3.4 and 2.4 fold in AM and non-AM plants, respectively) and amino acid (63 and 46% in AM and non-AM plants, respectively) content were significantly increased in AM plants over non-AM plants on 8 d of drought stress. Similarly, activities of SOD (superoxide dismutase), APX (ascorbate peroxidase) and GPX (guaiacol peroxidase) were higher in AM plants as compared to non-AM plants. Lipid peroxidation (83 and 129% in AM and non-AM plants, respectively) was more pronounced in non-AM plants as compared to AM plants on 12 d of imparting drought stress. Reduction in total chlorophyll content (63 and 85% in AM and non-AM plants, respectively) and activities of photosystem I (33 and 42% in AM and non-AM plants, respectively) and photosystem II (27 and 57% in AM and non-AM plants, respectively) was more evident in non-AM plants as compared to AM plants. The maximum quantum efficiency of PS II primary photochemistry (Fv/Fm), potential photochemical efficiency (Fv/Fo) and the maximal fluorescence (Fm) were higher in AM plants than non-AM plants. Based on these results, it can be deduced that the AM association helps the acclimation of S. spontaneum grown in drought stress conditions. AM association aid in enhancing the inherent drought tolerance potential of S. spontaneum by maintaining better osmotic status and enhanced antioxidation which have resulted in lesser decline of total chlorophyll and photosynthetic capacity.
In order to know the impact of elevated level of UV-B on arsenic stressed Helianthus annuus L. var. DRSF-113 plants, certain physiological (growth– root and shoot lengths, their fresh masses and leaf area; photosynthetic competence and respiration) and biochemical parameters (pigments– Chl a and b, Car, anthocyanin and flavonoids; reactive oxygen species– superoxide radicals, H2O2; reactive carbonyl group, electrolyte leakage; antioxidants– superoxide dismutase, peroxidise, catalase, glutathione-S-transferase, proline) of their seedlings were analysed under the simultaneous exposures of two arsenic doses (6 mg kg⁻¹ soil, As1; and 12 mg kg⁻¹ soil, As2) and two UV-B doses (1.2 kJ m⁻²d⁻¹, UV-B1; and 3.6 kJ m⁻²d⁻¹, UV-B2). As1 and As2 alone declined all the studied growth parameters– along with photosynthetic pigments which were further aggravated after the simultaneous exposures of predefined levels of UV-B. Each As exposure was accompanied by significant accumulation of As in root, shoot and leaves and was substantiated by simultaneous exposures of UV-B doses which manifested into suppressed growth, decreased chlorophyll contents and photosynthesis. In similar conditions, other photo-shielding pigments, viz. carotenoids, anthocyanin and flavonoids along with respiration and oxidative stress markers such as O2•¯, H2O2; and indicators of cell membrane damage like MDA (malondialdehyde), RCG (reactive carbonyl group), electrolyte leakage were enhanced by As, and became more pronounced after the simultaneous exposures of UV-B doses. As doses stimulated the activities of SOD, POD, CAT, GST and Pro which got further accelerated after the simultaneous exposures of UV-B doses.
In the present study, effect of different levels of nitrogen (N0, deprived; N25, sub-optimum; N75, optimum and N150, supra-optimum) in Solanum lycopersicum L. seedlings under NaCl (NaCl1, 0.3 g kg-1 and NaCl2, 0.5 g kg-1) stress was investigated. Biomass accumulation, pigments, K+ concentration, nitrate and nitrite contents were declined by NaCl in dose dependent manner. As compared to control (N75 without NaCl), fresh weight declined by 4% and 11% and dry weight by 7 and 13% when seedlings were grown under N75+NaCl1 and N75+NaCl2 combinations, respectively. Furthermore, fluorescence parameters (JIP-test): the size and number of active reaction centres of photosynthetic apparatus (Fv/F0), efficiency of water splitting complex (F0/Fv), quantum yield of primary photochemistry (φP0 or Phi_P0), yield of electron transport per trapped excitation (Ψ0 or Psi_0), the quantum yield of electron transport (φE0), and performance index of PS II (PIABS) and parameters related to energy fluxes per reaction centre (ABS/RC, TR0/RC, ET0/RC and DI0/RC) were also affected by NaCl. However, toxic effect of NaCl on photosystem II photochemistry was ameliorated by N. The lower dose (NaCl1) of NaCl exerts damaging effect on oxidation side of PS II, while higher dose (NaCl2) damages PS II reaction centre and its reduction side. Moreover, control seedlings (N75 without NaCl) when exposed to NaCl1 and NaCl2 exhibited a significant enhancement in respiration rate by 6 and 16%, Na+ accumulation by 111 and 169% in shoot, and 141 and 223 % in root and ammonium contents by 19 and 34%. Nitrate and ammonium assimilating enzymes such as nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS) and glutamate synthase (GOGAT) were adversely affected by NaCl stress while glutamate dehydrogenase (GDH) showed reverse trend. N addition caused enhancement in NaCl-mediated decline in endogenous proline, and activity of Δ1-pyrroline-5-carboxylate synthetase (P5CS), while activity of proline dehydrogenase decreased. The results indicate that different levels of N significantly modulated NaCl-induced damaging effects in tomato seedlings. Furthermore, the results suggest that after N addition Na+, nitrite, nitrate, ammonium contents, nitrogen metabolic enzymes, proline content, and activity of Δ1-pyrroline-5-carboxylate synthetase are favourably regulated, which might be associated with mitigation of NaCl stress and effect was more pronounced with supra-optimum level of N (N150).
Moringa oleifera leaf extract (MLE) is rich in amino acids, ascorbate, zeatin, minerals, and many other compounds known for their growth-promoting potential. Therefore, a pot experiment was aimed to study the effect of foliar spray with aqueous extracts of Moringa oleifera leaves on some physiological, biochemical, and molecular markers of common bean plants (Phaseolus vulgaris) grown under salt stress (200 mM), high temperature (45 °C), and gamma rays (200 Gy). The results showed that the shoot and root length, fresh and dry weights of shoots and roots, photosynthetic pigments, and phytohormone contents were decreased significantly in stressed plants as compared with untreated plants under all environmental stresses. On the other hand, total soluble sugars content, glutathione, malondialdehyde, O2•−, and H2O2 contents were significantly increased in stressed plants as compared to untreated plants. The exposure to different environmental stresses caused damage in leaf ultrastructure, which led to both vesiculation and swelling in the chloroplast stroma. In addition, many retrotransposons were showed to be activated in response to environmental stresses. Retrotransponson detecting the differences between control and stress samples in terms of different fragment length which reflects the effect of MLE and both stresses. The foliar application of moringa leaf extract caused significantly increased in all the above parameters. Results of this study suggested that MLE as antioxidant could activate the antioxidants in plants to enable them to alleviate the oxidative damage leading to improvements in physiological and molecular attributes in plants grown under the adverse conditions of environmental stresses.
Sesuvium portulacastrum is a facultative halophyte growing in coastal salt marshes. The aim of this study was to determine growth, physiological and biochemical traits of Sesuvium portulacastrum when subjecting pot-grown plants to different concentrations of NaCl supplemented with half strength Hoagland's nutrient solution to get the desired soil electrical conductivity (EC) of 0.3 (control), 4, 8, 12, 16, 20 dS m⁻¹. Enhancing salinity levels to 12 dS m⁻¹ resulted in concomitant increase in plant height, number of shoots per plant, number of leaves per plant and leaf area. Plants grown up to EC of 12 dS m⁻¹ exhibited higher net CO2 assimilation rate (PN), transpiration rate (E), and water use efficiency (WUE). Significant increases in electrolyte leakage and lipid peroxidation were observed in plants grown at EC 16 and 20 dS m⁻¹. Chlorophyll a and carotenoid pigment contents were significantly increased under high salt treatment (up to EC 16 dS m⁻¹) and chl a content was higher than chl b. Osmolyte accumulation as a function of osmotic adjustment and antioxidant enzyme activity (CAT, GR, SOD, APX and GPX) were maintained under salinity whereas significant Na⁺ sequestration and Na⁺/K⁺ ratio were evident with increase in salinity stress. A preliminary field experiment was conducted by using plants of S. portulacastrum grown for 90 days in control and saline soil of a field plot. The results showed that the desalination potential of the target species was reflected in the reduction of the soil electric conductivity in the salinized plots in addition to significant increases in the Na⁺ contents in the leaves of the salinity treated plants. To summarize, our results suggest that S. portulacastrum adapts to high salinity with better growth, photosynthesis, antioxidant defense and can be used in the desalination of saline lands.
Drought stress affects plants leaving a long-lasting imprint that may be passed onto progeny, affecting its growth and functioning. The aim of the research was to analyse the transgenerational effect of intense drought on alterations in functioning and changes in the growth of shoot and roots of spring barley. Barley seeds from a maternal generation that were affected by intense drought stress at the flag leaf stage or grown in the optimum conditions throughout the vegetation period were used as a sowing material to analyse the growth of a progeny generation at drought or in soil at optimum soil moisture. The difference in water availability during the growth of the progeny generation significantly affected all measured indicators of plant growth and functioning. However, significant differences were also found between offspring growing in the same conditions but characterised by different water availability during the growth of the maternal generation. The differences between plants with different stress histories in the maternal generation were more pronounced in barley offspring grown at drought than at optimum soil water availability. The drought induced during the growth of the barley maternal generation decreased the shoot-to-root mass ratio, enhanced growth of thin roots, and reduced the number of thick roots in the progeny grown at drought, compared to plants that were grown in the same conditions but without drought in the maternal generation. Maintenance of relatively long roots at low allocation of biomass to roots at drought in the progeny of the stressed maternal generation may be an adaptive response that can minimise carbon cost of water and nutrient acquisition.
In the present study, effect of different levels [0, 25,75 and 150 kg NO3− kg ha-1 sand correspond to N0 (deprived), N25 (sub-optimum), N75 (optimum) and N150 (supra-optimum)] of nitrate, respectively in eggplant (Solanum melongena L.) seedlings under NaCl (NaCl1, 0.3 g kg-1 and NaCl2, 0.5 g kg-1) stress was investigated. Growth, photosynthetic pigments and K+ ion content in test plant were declined by both the doses of NaCl. Furthermore, fluorescence parameters (JIP-test): Fm/F0, Fv/F0, Fv/Fm or φP0, φE0, Ψ0, PIABS, ABS/RC, TR0/RC, ET0/RC and DI0/RC were also affected by NaCl but toxic effects of NaCl on photosystem II photochemistry were ameliorated by N. NaCl increased accumulation of Na+ ion and oxidative stress biomarkers: superoxide radical, hydrogen peroxide, lipid peroxidation and electrolyte leakage despite increased activities of superoxide dismutase, peroxidase, catalase and glutathione-S-transferase. N addition caused enhancement in NaCl-mediated decline in endogenous proline and activity of Δ1-pyrroline-5-carboxylate synthetase (P5CS), while the activity of proline dehydrogenase decreased. The results indicate that different levels of N significantly modulated NaCl-induced damaging effects in eggplant. Further, results suggest that after N addition Na+ ion content, enzymatic antioxidants, and pool of free proline and activity of P5CS are finely regulated, which might be associated with the mitigation of NaCl stress and this effect was more pronounced with supra-optimum level of N.
Micro-nutrient application is essential for normal plant growth while a little is known about manganese (Mn)-induced regulations in morpho-physiological attributes, aroma formation and enzyme involved in 2-acetyl-1-pyrroline (2-AP) biosynthesis in aromatic rice. Present study aimed to examine the influence of four levels of Mn i.e., Mn1 (100 mg MnSO4 pot-1), Mn2 (150 mg MnSO4 pot-1), Mn3 (200 mg MnSO4 pot-1), and Mn4 (250 mg MnSO4 pot-1) on the growth, yield formation, quality characters, rice aroma and enzyme involved in 2-acetyl-1-pyrroline biosynthesis in two fragrant rice cultivars i.e., Meixiangzhan and Nongxiang 18. Pots without Mn application were served as control (Ck). Each pot contained 15 kg of soil. Effects on agronomic characters, quality attributes, 2-AP contents and enzymes involved in 2-AP biosynthesis have been studied in early and late season rice. Results depicted that Mn improved rice growth, yield and related characters, and some quality attributes significantly. It further up-regulated proline, pyrroline-5-carboxylic acid (P5C) (precursors of 2-AP), soluble proteins and activities of proline dehydrogenase (ProDH), Δ1 pyrroline-5-carboxylic acid synthetase (P5CS) ornithine aminotransferase (OAT) that led to enhanced 2-AP production in rice grains. Moreover, higher Mn levels resulted in increased grain Mn contents in both rice cultivars. Along with growth and yield improvement, Mn application significantly improved rice aromatic contents. Overall, Nongxiang 18 accumulated more 2-AP contents than Meixiangzhan in both seasons under Mn application. This study further explored the importance of Mn in rice aroma formation and signifies that micro-nutrients can play significant roles in rice aroma synthesis; however, intensive studies at molecular levels are still needed to understand the exact mechanisms of Mn to improve rice aroma formation.
Proline plays an important role in plant response to various environmental stresses. However, its involvement in mitigation of heavy metal stress in plants remains elusive. In this study, we examined the effectiveness of exogenous proline (10 and 20 mM) in alleviating cadmium induced inhibitory effects in young olive plants (Olea europaea L. cv. Chemlali) exposed to two Cd levels (10 and 30 mg CdCl2 kg(-1) soil). The Cd treatment induced substantial accumulation of Cd in both root and leaf tissues and a decrease in gas exchange, photosynthetic pigments contents, uptake of essential elements (Ca, Mg and K) and plant biomass. Furthermore, an elevation of antioxidant enzymes activities (superoxide dismutase, catalase, glutathione peroxydase) and proline content in association with relatively high amounts of hydrogen peroxide, thiobarbituric acid reactive substances and electrolyte leakage were observed. Interestingly, the application of exogenous proline alleviated the oxidative damage induced by Cd accumulation. In fact, Cd-stressed olive plants treated with proline showed an increase of antioxidant enzymes activities, photosynthetic activity, nutritional status, plant growth and oil content of olive fruit. Generally, it seems that proline supplementation alleviated the deleterious effects of young olive plants exposed to Cd stress.
Apricot production is mostly located in areas of Iran, where flowering is damaged by temperatures. Using plant growth regulators to decrease spring frost damage is suggested as a measure to avoid frost damage. The objective of this study was to determine the effects of nitric oxide treatment on avoiding spring frost damage apricot. We evaluated applications of nitric oxide (NO) 0 (control, water only), 10 and 15 μM at green tip and pink tip stages of ‘Thokhm Gerdi’ apricot then treated shoots were collected and cutting sections were placed in incubator and subjected to sequential freezing temperature, −1, and −3 °C, held for 30 min at each temperature. The NO treatment decreased freezing injury, lipid peroxidation and ion leakage percentage for flowers after freezing tests at treatment both stages (especially pink tip stage and −3 °C) compared with control. The results showed No application increased significantly proline, inducing sugar, ascorbate peroxidase, superoxide dismutase, catalase, peroxidase enzyme activity and DPPH-radical scavenging activity of flowers. These results showed that NO affects antioxidant capacity of flowers and changes solute content (proline, inducing sugar). Moreover, NO treatment protects apricot flowers from freezing and spring frost damage. So, the present study is the first evidence that nitric oxide effects on avoiding spring frost damage of apricot.
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Seed priming is a technique which is potentially able to promote rapid and more uniform seed germination and plant growth. In order to study the effects of seed priming treatments on some physiological and biochemical parameters, black cumin seeds were subjected to hormopriming and halopriming. The results indicated that germination percentage and rate were not impressed by cadmium. Radicle length was reduced more than plumule length and was expressed as the sensitivity index. Hormopriming (100mg/L of salicylic acid) improved the germination, radicle elongation and dry weight (30.74, 42, and 31.57%, respectively) in compared with the control under cadmium stress (30mgL-1). The maximum plumule elongation and plumule dry weight were related to the seeds primed with KNO3 about 48.61 and 25%, respectively. Increase in cadmium concentration until 30mg/L increased electrical conductivity, malondialdehyde (MDA) and proline content for the all priming treatments and unprimed seeds, although in primed seeds was lower than that unprimed seeds. In highest cadmium concentration (30mg/L), POX activity significantly increased in SA, KNO3 and KCl treatments about 56.25, 50 and 40.62% as compared with control, respectively. The reduction in soluble protein was observed in unprimed and primed seedlings with SA, KNO3 and KCl under highest cadmium concentration. In conclusion, the seed priming with SA due to improve germination performance of black cumin in different Cd levels can enhance tolerance of seedlings to toxic metals stress in the irrigation water.
The current work aims to assess whether the rootstock can improve the salinity tolerance of an almond cultivar. The study included a description of the physiological and biochemical adaptations of one-year old scions of Mazzetto grafted onto either GF677 or Garnem rootstocks and exposed to increasing concentrations of NaCl in the growing medium. The plants were watered with a nutrient solution containing 0 mM (control), 25 mM, 50 mM or 75 mM NaCl. There was a significant reduction in shoot extension in response to increasing NaCl concentration in the growing medium especially in the plants grafted onto GF677. The better shoot growth of Mazzetto/Garnem plants appears to be due to their ability to limit the loss of photosynthetic activity by maintaining stomatal conductance and protecting chlorophyll and cytosolic assimilatory enzymes from toxic ions. Leaves of Mazzeto/Garnem had higher gs rates, carotenoids/chlorophyll and anthocyanins/chlorophyll ratios and a better nutritional status (higher K+ and Ca2 + and lower Na+) compared to Mazzeto/GF677. Furthermore, the former maintained higher proline and soluble sugar concentrations and lower leaf water potential. Our results suggest that Garnem offers a degree of protection against salinity which can be exploited in breeding programmes.
This study was aimed at examination of physiological and agronomic responses of fennel (Foeniculumvulgare Mill.) to water deficit. Twelve fennel genotypes namely ‘Kashan’, ‘Urmia’, ‘Hamadan’, ‘Kerman’,‘Shiraz’, ‘Birjand’, ‘Mashhad’, ‘Ardabil’, ‘Bushehr’, ‘Avicenna’, ‘Isfahan’, and ‘Yazd’ were subjected to fourlevels of irrigation (irrigation after 35%, 55%, 75%, and 85% depletion of available soil water) in a field studyin two years. Leaf water potential, relative water content (RWC), proline, total soluble sugars, chlorophylla (Chl a), b (Chl b), total (Chl a + b), a/b (Chl a/b) along with dry mass (DM), seed yield and its attributes andseed essential oil content were measured. Water deprivation left significant effects on all characteristics,i.e. in contrast to seed essential oil content and harvest index, the rest of the attributes were decreasedsignificantly with drought intensification. Varietal differences in response to drought were meaningfulfor most of the traits; i.e. genotypic variations for DM, grain yield and stress susceptibility index (SSI)were consistent with differences among the genotypes in physiological traits such as leaf water potential,RWC, proline, soluble sugars and chl content. Genotypes were discriminated according to their responseto drought and SSI. Drought tolerant genotypes (‘Yazd’, ‘Kerman, ‘Mashhad’ and ‘Shiraz’) exhibited agreater capacity for accumulation of osmotic solutes associated with higher leaf water potential andRWC, compared to drought sensitive genotypes (‘Ardabil’, ‘Avicenna’, ‘Hamadan’ and ‘Birjand’). Fromour findings, fennel could be appreciated as a promising species in potentiating alternative industrial-medicinal crops in the face of the eminent challenge of water scarcity in arid and semi-arid climaticregions.
Shoot-tip derived callus cultures of Sorghum bicolor were transformed by Agrobacterium tumefaciens as well as by bombardment methods with the mutated pyrroline-5-carboxylate synthetase (P5CSF129A) gene encoding the key enzyme for proline biosynthesis from glutamate. The transgenics were selfed for three generations and T4 plants were examined for 100 mM NaCl stress tolerance in pot conditions. The effect of salt stress on chlorophyll and carotenoid contents, photosynthetic rate, stomatal conductance, internal carbon dioxide concentration, transpiration rates, intrinsic transpiration and water use efficiencies, proline content, MDA levels, and antioxidant enzyme activities were evaluated in 40-day-old transgenic lines and the results were compared with untransformed control plants. The results show that chlorophyll content declines by 65% in untransformed controls compared to 30-38% loss (significant at P < 0.05) in transgenics but not carotenoid levels. Photosynthetic rate (PSII activity) was reduced in untransformed controls almost completely, while it declined by 62-88% in different transgenic lines. Salinity induced ca 100% stomatal closure in untransformed plants, while stomatal conductance was decreased only by 64-81% in transgenics after 4 days. The intercellular CO2 decreased by ca 30% in individual transgenic lines. Malondialdehyde (MDA) content was lower in transgenics compared to untransformed controls. The activities of superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6) and glutathione reductase (GR; EC1.8.1.7) were quantified in leaves exposed to 100 mM NaCl stress and found higher in transgenics. The results suggest that transgenic lines were able to cope better with salt stress than untransformed controls by protecting photosynthetic and antioxidant enzyme activities.
Copyright © 2015 Elsevier Masson SAS. All rights reserved.
The free proline levels and activities of pyrroline-5-carboxylate reductase, proline oxidase and proline dehydrogenase and the levels of quaternary ammonium compounds and chlorophyll stability were studied during water stress in drought sensitive (S54) and drought tolerant (S13) cultivars of mulberry (Morus alba L.). The cultivar S13 accumulated relatively greater amounts of free proline compared with S54. Water stress increased about 8- and 3.5-fold in free proline content in the third leaf from the top, of S13 and S54 respectively, after 15 days of severe water stress. The pyrroline-5-carboxylate reductase was increased, while the activities of proline oxidase and proline dehydrogenase were significantly decreased in both cultivars under water stress conditions. However, the magnitude of increase in pyrroline-5-carboxylate reductase was relatively greater and the degree of decrease in proline oxidase and proline dehydrogenase activities was relatively small in S13 compared with S54. The results indicate that during water stress, proline metabolism was altered in mulberry and the eitent of alteration varied between the cultivars S13 and S54, leading to the greater levels of proline in S13, supporting its drought tolerance. The greater proline levels in S13 were due both to the higher rates of proline synthesis and lesser magnitude of proline oxidation compared with S54. Further, the drought tolerance of S13 was evident from the greater magnitude of accumulation of quaternary ammonium compounds compared with S54 during water stress. Furthermore, the drought tolerance of S13 was supported by chlorophyll stability, having comparatively lower amounts of chlorophyll breakdown.
Changes in plant antioxidant enzymes (AOEs) in response to cadmium (Cd) pollution are an important mechanism for plant growth and tolerance to Cd-induced stress. The main objective of this greenhouse study was to determine the combined influence of earthworm and arbuscular mycorrhiza (AM) fungal inoculation and their interactions with Cd on AOEs and proline accumulation in leaves of two major crops under Cd stress. Maize (Zea mays L.) and sunflower (Helianthus annuus L.) plants were exposed to Cd stress (10 and 20 mg kg−1 soil), inoculated with either earthworm (Lumbricus rubellus L.) or AM fungi (Glomus intraradices and Glomus mosseae species) in a pot experiment for three months. Exposure to Cd decreased shoot dry weights, increased shoot Cd and P concentrations, leaf proline accumulation and the activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and polyphenol oxidase (PPO) in both mycorrhizal and non-mycorrhizal plants and both in the presence and absence of earthworms. Inoculation of both model plants with earthworms and AM fungi decreased shoot Cd concentrations and the activity of all AOEs, except PPO. Although earthworm activity enhanced the proline content of sunflower in Cd-polluted soils, the proline level of both plants remained unaffected by AM fungi. AM fungi and earthworms may decrease the activity of AOEs through a decline in shoot Cd toxicity and concentration, confirming that plant inoculation with these soil organisms improves maize and sunflower tolerance and protection against Cd toxicity. Generally, the effect of AM fungal inoculation on plant responses to Cd addition was greater than that of earthworm activity. Nonetheless, the interactive effect of AM fungus and earthworm is of minor importance for most of the plant AOEs in Cd-polluted soils.
CuCl2 treatments led to a significant growth reduction, while pre-treatment with H2O2 increased plant growth compared to the control in sweet corn seedlings. The increment of the proline content in shoots followed in the order of H2O2 (6 h)+ CuCl2 > H2O2 > CuCl2 > Control. During only H2O2 treatments the activities of Delta(1)-pyrroline-5-carboxylatesynthetase (P5CS) and glutamate dehydrogenase (GDH) of the glutamate path increased immediately, while Arginase and ornithine aminotransferase (OAT) of the ornithine path activities raised after 8 h treatments. Under CuCl2 stress Arginase and OAT activities rose quickly, P5CS and GDH activities also increased after 8 h treatments. The simultaneous increase of the proline content during CuCl2 stress might be related with the sequential activation of the ornithine and glutamate pathways and a reduction in ProDH. Pre-treatment with H2O2 induced an almost immediate and rapid increase of activities of Arginase and OAT, P5CS and GDH. The treatments also decreased the activity of proline dehydrogenase, a key enzyme of proline degradation. At the same time, pre-treatment with H2O2 induced an additional increase of the enzymes expression of ornithine pathway and glutamate pathway, while an additional decline was also observed in the expression of ProDH in sweet corn seedling under CuCl2 stress. While pre-treated with H2O2 under CuCl2 stress inducing proline content was a combined result of activation of the ornithine and glutamate pathways and a reduction in ProDH. It was, therefore, concluded that H2O2 ameliorated the stress generated by CuCl2 through the enhancing proline content. Overall, the adverse effects of CuCl2 stress could be alleviated by exogenous application of H2O2.
Plant-derived protein hydrolysates represent new biostimulant products able to improve crop tolerance
to abiotic stresses. The aim of the study was to determine growth, root morphology, SPAD index,
chlorophyll fluorescence, leaf mineral composition, and metabolic profiling of greenhouse lettuce either
untreated or treated (root or leaf-root application) with a plant-derived protein hydrolysate. For foliar
application, plants were sprayed with a solution containing 2.5 ml L−1 of biostimulant, whereas for root
application, 100 mL of solution with the same concentration was applied to the growing medium at
weekly intervals. Lettuce plants were supplied with two nutrient solutions: non-salt control (1 mM NaCl)
or 25 mM NaCl. Salt stress decreased shoot and root dry biomass, SPAD index, chlorophyll fluorescence,
leaf mineral composition and increased foliar proline concentration. Root and leaf-root application of
the biostimulant increased fresh yield, dry biomass and root dry weight of lettuce under salinity conditions.
This was associated with an improvement of plant nitrogen metabolism and an increase of the
Fv/Fm-ratio efficiency in biostimulant-treated plants. Oxidative stress mitigation, increase in osmolytes,
changes in sterols and terpenes composition, as well as the less expected increase in glucosinolates were
also observed in biostimulant-treated plants grown under saline conditions. The present study proves
that the application of plant-derived protein hydrolysate increases plant performance when plants are
grown under salinity conditions. The most favorable metabolic profile was obtained when biostimulant
was applied to both roots and leaves.
Traditional crops are extremely important for food production in low income, food-deficit countries (LIFDCs) where they continue to be maintained by socio-cultural preferences and traditional uses. Significant potential exists to improve these crops, one of which is to select for improved productivity during moisture stress conditions. Germplasm of Amaranthus tricolor, Amaranthus hypochondriacus and Amaranthus hybridus were subjected to various screening methods to measure metabolic and physiological changes during water stress. The activities of enzymes involved in the oxygen-scavenging system during abiotic stress conditions (superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR)), free proline production, leaf area (LA), cell membrane stability (CMS), leaf water potential (LWP) and relative water content (RWC) were measured in these three amaranth species during induced water stress. This study showed significant differences in metabolic responses during water deficit of the three species tested. Moisture stress and a decrease in RWC and LWP were first experienced in A. hybridus and A. hypochondriacus, followed by A. tricolor. There was an indirect correlation between leaf water status (RWC and LWP), enzyme activity, proline production and leaf area. The combined effect of GR, APX and SOD could ensure higher levels of regulation of the toxic effect of H2O2 which could be associated with drought tolerance in Amaranthus. Distinct differences in onset of proline accumulation and the amount of accumulated in leaves upon induced water stress was noticed for the three amaranth species tested. Proline accumulation during water stress conditions in amaranth seems to be indirect and could possibly have a protective role apart from osmoregulation during stress conditions. This contention is supported by the decrease in leaf area and high cell membrane stability for two of the species tested. This study forms part of a project aimed at the development of improved traditional crops to contribute to food production and quality for subsistence farmers in areas with low precipitation or variable rainfall patterns.
Pollution of antimony (Sb) raises a serious environmental problem. Although this non-essential element can be taken up by roots and accumulated in plant tissues in relatively high concentrations, there is still lack of knowledge about the effect of Sb on biochemical and metabolic processes in plants. It was shown that application of silicon (Si) can decrease the toxicity of other heavy metals and toxic elements in various plants. The aim of this study was to assess how Si influences the growth and antioxidative response of young Zea mays L. roots exposed to elevated concentrations of Sb. Antimony reduced the root growth and induced oxidative stress and activated antioxidant defense mechanisms in maize. Silicon addition to Sb treated roots decreased oxidative stress symptoms documented by lower lipid peroxidation, proline accumulation, and decreased activity of antioxidative enzymes (ascorbate peroxidase, EC 1.11.1.11; catalase, EC 1.11.1.6; and guaiacol peroxidase, EC 1.11.1.7). Although neither positive nor negative effect of Si has been observed on root length and biomass, changes in the oxidative response of plants exposed to Sb indicate a possible mitigation role of Si on Sb toxicity in plants.
The domestication of non-food salt resistant plants could be helpful for biofuel as well as phyto-remediation of salt-affected lands. Limited eco-physiological studies on halophytes are the major bottleneck in developing such plants as energy crops. The aim of the present work was to determine the effect of salt stress on growth, ion homeostasis, water status and photosynthesis of Phragmites karka - a potential biofuel crop. Plants were grown in 0, 100 and 300 mM NaCl (equivalent to non-saline, 20 and 60% seawater). Our results indicate that the addition of 100 mM NaCl to the growth medium increased plant biomass. Leaf osmotic adjustment was primarily achieved by inorganic solutes (K+ and Na+) while soluble sugars and proline remained unchanged. Higher K+ selectivity and Na+ exclusion from shoots improved photosynthesis and growth under moderately saline conditions. Decreased growth in 300 mM NaCl could be attributed to leaf tissue dehydration and turgor loss leading to stomatal closure and decreased CO2 absorption. Our results indicate that P. karka could produce high ligno-cellulosic biomass for ethanol production using brackish water irrigation on saline soils avoiding competition with conventional agriculture.
The effect of different concentrations of NaCl, 0, 100, 200, 300 and 400mM, on the anatomical features and physiology of Myoporum bontioides was investigated. The photosynthetic rates (Pn) were significantly reduced by salt stress, with the lowest values at 400mM NaCl. The content of malondialdehyde (MDA), proline and soluble sugar, as well as the activities of peroxidase (POD) and catalase (CAT) increased at the beginning, but became similar to the control as the experiment proceeded. The NaCl effect on superoxide dismutase (SOD) was different from the other parameters, with a significant reduction at 400mM NaCl at Day 7. Salt glands were found in both upper and lower epidermis, and the ratios of the thickness of palisade to spongy mesophyll tissues increased with NaCl concentrations. The medullary ray was clearly damaged by NaCl at levels of 200 and 300mM. These results demonstrated that M. bontioides could adapt to a relatively low salinity, and was not a halophilous species.
A vacuolar proton pyrophosphatase cDNA clone was isolated from Sorghum bicolor (SbVPPase) using end-to-end gene-specific primer amplification. It showed 80–90% homology at the nucleotide and 85–95% homology at the amino acid level with other VPPases. The gene was introduced into expression vector pCAMBIA1301 under the control of the cauliflower mosaic virus 35S (CaMV35S) promoter and transformed into Agrobacterium tumifaciens strain LBA4404 to infect embryogenic calli of finger millet (Eleusine coracana). Successful transfer of SbVPPase was confirmed by a GUS histochemical assay and PCR analysis. Both, controls and transgenic plants were subjected to 100 and 200 mM NaCl and certain biochemical and physiological parameters were studied. Relative water content (RWC), plant height, leaf expansion, finger length and width and grain weight were severely reduced (50–70%), and the flowering period was delayed by 20% in control plants compared to transgenic plants under salinity stress. With increasing salt stress, the proline and chlorophyll contents as well as the enzyme activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and glutathione reductase (GR) increased by 25–100% in transgenics, while malondialdehyde (MDA) showed a 2–4-fold decrease. The increased activities of antioxidant enzymes and the reduction in the MDA content suggest efficient scavenging of reactive oxygen species (ROS) in transgenics and, as a consequence, probably alleviation of salt stress. Also, the leaf tissues of the transgenics accumulated 1.5–2.5-fold higher Na+ and 0.4–0.8-fold higher K+ levels. Together, these results clearly demonstrate that overexpression of SbVPPase in transgenic finger millet enhances the plant's performance under salt stress.
Induction of stress ethylene production in the plant system is one of the consequences of salt stress which apart from being toxic to the plant also inhibits mycorrhizal colonization and rhizobial nodulation by oxidative damage. Tolerance to salinity in pea plants was assessed by reducing stress ethylene levels through ACC deaminase-containing rhizobacteria Arthrobacter protophormiae (SA3) and promoting plant growth through improved colonization of beneficial microbes like Rhizobium leguminosarum (R) and Glomus mosseae (G). The experiment comprised of treatments with combinations of SA3, G, and R under varying levels of salinity. The drop in plant biomass associated with salinity stress was significantly lesser in SA3 treated plants compared to non-treated plants. The triple interaction of SA3 + G + R performed synergistically to induce protective mechanism against salt stress and showed a new perspective of plant-microorganism interaction. This tripartite collaboration increased plant weight by 53%, reduced proline content, lipid peroxidation and increased pigment content under 200 mM salt condition. We detected that decreased ACC oxidase (ACO) activity induced by SA3 and reduced ACC synthase (ACS) activity in AMF (an observation not reported earlier as per our knowledge) inoculated plants simultaneously reduced the ACC content by 60% (responsible for generation of stress ethylene) in SA3 + G + R treated plants as compared to uninoculated control plants under 200 mM salt treatment. The results indicated that ACC deaminase-containing SA3 brought a putative protection mechanism (decrease in ACC content) under salt stress, apart from alleviating ethylene-induced damage, by enhancing nodulation and AMF colonization in the plants resulting in improved nutrient uptake and plant growth.
This study investigates largely unexplored physiological/biochemical strategies adopted by salt marsh macrophyte Halimione portulacoides (L.) Aellen for its adaptation/tolerance to environmental mercury (Hg)-exposure in a coastal lagoon prototype. To this end, a battery of damage (hydrogen peroxide, H2O2; thiobarbituric acid reactive substances, TBARS; electrolyte leakage, EL; reactive carbonyls; osmolyte, proline) and defense [ascorbate peroxidase, APX; catalase, CAT; glutathione peroxidase, GPX; glutathione sulfo-transferase, GST; glutathione reductase, GR; reduced and oxidized glutathione (GSH and GSSG, respectively), and GSH/GSSG ratio] biomarkers, and polypeptide patterns were assessed in H. portulacoides roots and leaves at reference (R) and the sites with highest (L1), moderate (L2) and the lowest (L3) Hg-contamination gradients. Corresponding to the Hg-burdens, roots and leaves exhibited a differential modulation of damage- and defense-endpoints and polypeptide-patterns. Roots exhibiting the highest Hg-burden (at L3) failed to maintain a coordination among enzymatic-defense endpoint responses which resulted into increased oxidation of reduced glutathione (GSH) pool, lowest GSH/GSSG (oxidized) ratio and partial H2O2-metabolism. In contrast, the highest Hg-burden exhibiting leaves (at L1) successfully maintained a coordination among enzymatic-defense endpoints responses which resulted into decreased GSH-oxidation, enhanced reduced GSH pool and GSH/GSSG ratio and lower extent of damage. Additionally, increased leaf-carotenoids content with increasing Hg-burden implies its protective function. H. portulacoides leaf-polypeptides did not respond as per its Hg-burden but the roots did. Overall, the physiological/biochemical characterization of below (roots)- and above (leaves)-ground organs (studied in terms of damage and defense endpoints, and polypeptides modulation) revealed the adaptive responses of H. portulacoides to environmental Hg at whole plant level which cumulatively helped this plant to sustain and execute its Hg-remediation potential.
Experiments were conducted to evaluate the effects of combined water salinity and deficit irrigation on common bermudagrass in order to address the shortage of water resources and increasing water and soil salinity in arid and semi-arid zones. This study was carried out under greenhouse conditions in a completely randomized design with factorial arrangements. Treatments included 4 water salinity levels (0.5, 3, 6 and 9 dS m− 1) and 4 deficit irrigation regimes (2, 4, 6 and 8 day intervals). Results indicated a rise in ion leakage, soluble sugars and proline concentrations; and a drop in leaf relative water content (RWC), leaf chlorophyll content and photosynthetic rate with increasing levels of both stresses. Antioxidant enzymes, superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7) and ascorbate peroxidase (APX, EC 1.11.1.11) showed higher activity under moderate drought or salinity conditions. However, these enzyme levels dropped at higher levels of these two stresses. Based on the results of the present study, common bermudagrass could be grown under moderate combined water and salinity stresses without considerable damage to plants at the physiological and/or biochemical level. This is the first report of applying combined water and salinity stresses to an important turfgrass species. Further studies are needed to evaluate the effects of these stresses on characteristics of bermudagrass at the molecular and ultrastructural levels.
The quality traits of fruit harvested from ‘Fortune’ mandarin trees (Citrus clementina Hort. Ex. Tanaka × C. reticulata Blanco) subjected to different irrigation strategies was studied at harvest, during cold storage (33 d at 5 °C), and after an additional shelf-life period of 5 d at 25 °C. Plant water status was also determined in the pre-harvest period. Irrigation treatments consisted of a control irrigated at 100% of crop evapotranspiration throughout the season, and two deficit irrigation treatments irrigated during the fruit growth period to maintain the ratio between the fruit growth rate (FGR) of the control trees and those of the water deficit treatment (signal intensity, SIFGR) at two different water stress levels: (i) Severe (DI10) when this ratio was around 1.1 (SIFGR), and (ii) moderate (DI5) when it was around 1.05. The amount of water applied in DI10 and DI5 represented a reduction of 40% and 29%, respectively, compared with the control. No negative effects on the yield parameters studied were observed. During the second fruit growth stage, differences in stem water potential at midday of around 0.4 and 0.9 MPa in DI5 and DI10 treatments, respectively, respect control promoted a significant decrease in FGR. Overall, both DI treatments improved fruit quality at harvest due to increased total soluble solids and juice proline content, fruit maintained their quality longer during storage than the control. Cold stored fruit of both DI treatments presented similar fruit hardness values but a higher juice proline content, total soluble solids and titratable acidity, and, as a consequence, a lower maturity index than the control. At the end of storage, DI fruit showed a thicker skin and lower commercial losses due to chilling injury.
This study investigates the impact of different single-bilayer graphene oxide sheet (hereafter 'graphene oxide', GO; size: 0.5-5μm) concentrations (0, 100, 200, 400, 800 and 1600mgL(-1)) and underlying potential mechanisms in germinating faba bean (Vicia faba L.) seedlings. The study revealed both positive and negative concentration-dependent GO-effects on V. faba. Significant negative impacts of GO concentrations (ordered by magnitude of effect: 1600>200>100mgGOL(-1)) were indicated by decreases in growth parameters and the activity of H2O2-decomposing enzymes (ascorbate peroxidase, APX; catalase, CAT), and by increases in the levels of electrolyte leakage (EL), H2O2, and lipid and protein oxidation. The positive impacts of 400 and 800mgGOL(-1) included significant improvements in V. faba health status indicated by decreased levels of EL, H2O2, and lipid and protein oxidation, and by enhanced H2O2-decomposing APX and CAT activity, and increased proline and seed-relative water content. V. faba seedlings-polypeptide patterns strongly substantiated these GO-concentration effects. Overall, the positive effects of these two GO concentrations (800>400mgL(-1)) on V. faba seedlings indicate their safe nature and allow to suggest further studies.
Seeds of Chinese cabbage (Brassica rapa pekinensis) were treated with serial concentrations of perfluorooctane sulfonate (PFOS) for observation of germination and development. Germination rate, growth process and various physiological indicators of the seedlings were analyzed. Inhibition of germinability rate (by 10.0 percentages), germination rate (by 8.3 percentages), and growth (by seedling falling or death) by 85 mg/L PFOS were observed. Chlorophyll content, dissolvable protein content, catalase activity, peroxidase activity and superoxide dismutase activity in the leaves were inhibited by PFOS dose ≥ 51 mg/L (P<0.05). PFOS also resulted in an increasing of free proline content in the leaves of seedlings (P<0.05).
The effect of salinity and iron deficiency on growth, proline, carbohydrate and ion content in Chamomile (Matricaria chamomilla L.) was evaluated in controlled environment. Salinity treatment was 0, 50, 100 and 150 mM NaCl in nutrient solution and iron (Fe) treatment was F0 = the same nutrient solution without Fe and F1 = standard nutrient solution containing 100 μM Fe (Fe-sufficient medium). Results indicated that increasing salinity from 0 to 150 mM, decreased fresh weight of shoot (76.3%) and increased of root fresh weight (53.8%). However, application of Fe to the nutrient solution significantly increased fresh weight of root and shoot. A two-way ANOVA indicated a significant main effect of salinity and iron on the proline and soluble carbohydrate contents in plant leaves. Salinity significantly increased proline and soluble carbohydrate in leaves. Maximum proline and carbohydrate content in leaves of chamomile plants were obtained at salinity and iron deficiency treatments. Salinity treatment significantly increased Na+ concentration of plants, whereas potassium concentration of plants in shoot (37.6%) and root (46.1%) decreased. Salinity also decreased Fe content in root and shoot of chamomile plants. By application Fe into nutrient solution, Na+ concentration in shoot and root decreased but K+ and Fe content in root and shoot increased.
Arbuscular mycorrhiza (AM) constitutes a key functional group of soil biota that can greatly contribute to ecosystem sustainability by playing a critical role in stress tolerance. The effects of arsenic (As) stress on physiological and biochemical mechanisms and the role of Glomus mosseae (AM) in reducing As accumulation was investigated in Pisum sativum L. (pea). As uptake and accumulation increased with an increase in external As concentration, increment being higher in roots than in shoots. Sodium arsenate significantly affected shoot and root dry matter yield, damaged chlorophyll pigments and induced oxidative stress by decreasing membrane stability and increasing H2O2 production in a concentration dependent manner. The phytotoxicity of arsenate (AsV) led to an increase in superoxide dismutase, catalase and peroxidase activities and synthesis of osmolytes such as soluble sugars, proline, glycine betaine and total proteins. Establishment of association with G. mosseae reduced As(V) uptake and increased N, P, K+ as well as plant growth. AM inoculations alleviated As(V) toxicity by reducing oxidative stress and modulating antioxidative mechanisms in pea plants.
Excessive accumulation of reactive oxygen species (ROS) under salt stress can cause oxidative damage, nitric oxide (NO) is considered as a functional molecule in alleviating salt stress to plants through modulating antioxidant metabolism. In the present experiment, effects of sodium nitroprusside (SNP), a NO donor, on the growth, and antioxidant capacity of cucumber hypocotyls and radicles as well as root tip ultrastructure were studied under 100 mM NaCl stress. NaCl treatment significantly induced accumulation of H2O2 and thiobarbituric acid-reactive substances (TBARS) in cucumber hypocotyls and radicles, and application of 100 μM SNP stimulated ROS-scavenging enzymes and increased α,α-diphenyl-β-picryllhydrazyl (DPPH) scavenging activity, chelating activity of ferrous ions and hydroxyl radical (OH) scavenging activity, resulting in lower lipid peroxidation induced by NaCl stress. The ultrastructure of the root tip cells was investigated, NaCl stress induced disturbance of mitochondria and the cell wall, and SNP treatment alleviated the ultrastructure disturbance induced by NaCl stress. The above effects of SNP were reversed by addition of hemoglobin (a NO scavenger), which indicated that the function of SNP alleviating lipid perioxidation in NaCl-treated cucumber hypocotyls and radicles depended on NO. Therefore, it can be concluded that the increasing antioxidant capacity by NO might be greatly responsible for its function in alleviating the inhibition of cucumber hypocotyls and radicles growth and cell ultrastructure damage by salt stress.
It is well known that heavy ions irradiation is characterized by a high linear energy transfer (LET) and relative biological effectiveness (RBE). These characters are believed to increase mutation frequency and mutation spectrum of plants or mammalian cells irradiated by heavy ions. Here we describe an early-maturity mutant of sweet sorghum induced by carbon ion irradiation. The growth period of this mutant was shortened by about 20 days compared to the wild type. The proline content of the mutant was increased by 11.05% while the malondialdehyde content was significantly lower than that of wild type. In addition, the RAPD analysis indicated that the percentage of polymorphism between the mutant KFJT-1 and the control KFJT-CK reached 5.26%. The gain of early-maturity might solve the problem in the northwest region of China where seeds of sweet sorghum cannot be mature because of early frost. The early-maturity mutant may be important for future space cultivation.
The influence of NaCl or Na2SO4 on glutamate, proline and glycine betaine contents and the activities of pyrroline-5-carboxylate (P5C) reductase, proline dehydrogenase and proline oxidase was studied in greengram seedlings. The levels of glutamate decreased. Consequently, proline accumulated substantially in roots and shoots of stressed seedlings; glycine betaine content increased in the tissues. The activity of P5C reductase was enhanced while proline dehydrogenase and proline oxidase were inhibited to a great extent. Further, the response of these enzymes to salt stress is discussed.
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