Search

Copper (Cu) is an essential micronutrient prerequisite for various metabolic processes in plants. At optimum concentration, it performs a vital role in plant growth and development, while as at supra-optimal levels, it disturbs the normal growth in plants. Due to its dual behavior (vital and harmful), the present experiment was designed to assess the potential role of different Cu concentrations (30, 60, and 90) on Brassica juncea cv. Varuna plants. The experiment was set up in a randomized block design, and various physiological, biochemical, microscopic, and histochemical parameters were assessed at 30, 45, and 60 days after sowing. According to our findings, Cu inhibits growth at all concentrations over the control. The maximum reduction was reported in plants cultivated on Cu 90 mg kg−1 of soil. Cu inhibits the chlorophyll content, RUBISCO activity, photosynthetic parameters, PSII activity, electron transport, and maximum quantum yield, at all concentrations. Cu stress decreases nitrate reductase and carbonic anhydrase activity as well as reduction in relative water content and carbohydrate levels in treated plants. Cu levels induced oxidative stress molecules like reactive oxygen species and malondialdehyde content in test plants, due to which the enzymatic antioxidants (catalase, superoxide-dismutase, and peroxidase) as well as non-enzymatic antioxidants (glutathione, proline), were unregulated. Excess Cu level disturbs the essential nutrient and decreases the levels of nitrogen, phosphorus, and potassium while elevated levels of Cu were observed in test plants. From the above findings, we conclude that Cu displayed a toxic effect at all the concentrations and reduced growth, photosynthetic parameters, and biochemical parameters in Brassica juncea.

Nitric oxide (NO) plays a vital role in plant defense against various environmental stresses. However, the study on the defensive effect of NO on the phytotoxicity induced by zinc oxide nanoparticles (ZnO-NPs) remains scarce. In the present study, sodium nitroprusside (SNP, a NO donor) was used to investigate the mechanism of NO in ameliorating the ZnO-NPs toxicity in mustard (Brassica juncea (L.) Czern.) plants. The plants were treated with the different concentrations of SNP (100 µM) and ZnO-NPs (1000 and 2000 µM) either alone or in combination at 25 days after sowing (DAS) for five days consecutively. The results of our study shows that 100 µM of SNP proved highly effective in mitigating the toxicity induced by ZnO-NP. SNP significantly improve chlorophyll content that partially improve photosynthesis in ZnO-NPs stressed plants. Moreover, the defensive role of SNP in relieving the oxidative damage induced by ZnO-NPs is intimately linked to NO-induced antioxidative defense system. The spray of SNP increased the growth biomarkers as well as proline content in control as well as in ZnO-NPs-treated plants. Additionally, microscopic studies further reveal an increase in the size of stomatal aperture on SNP exposure in ZnO-NPs treated plants. Overall, this study provides the first evidence indicating the functions of SNP in alleviating the ZnO-NPs toxicity in mustard plants.

It is known that auxin and nitric oxide have the ability to ameliorate various abiotic stresses in plants individually. However, their interactive effects on the stress generated by salt in plants are not reported yet. Therefore, the present study was conducted to explore the effectiveness of sodium nitroprusside (SNP), a donor of nitric oxide and IAA (Indole acetic acid) individually and in combination on the photosynthetic efficiency, antioxidative enzyme activities, and plant biomass under salt stress. Twenty-five-day-old plants were exposed to SNP and IAA individually and in combination for 5 days continuously, and it was found that both SNP and IAA showed almost similar response at 30 and 45 days of old plants and increased studied parameters over their respective controls. However, the interactive effect of both SNP and IAA excelled over the individual response of SNP and IAA. On the other hand, the presence of salt in soil significantly decreased the parameters studied. Furthermore, stress generated by NaCl was overcome by the exogenous application of SNP, IAA alone as well as in combination at both the stages of samplings. However, the combination of IAA and SNP was more effective at 45 DAS where the value of plant biomass and photosynthetic efficiency was more in comparison to control plants. The level of antioxidant enzymes and proline was further enhanced by SNP and IAA and maximum values were reported in the plants received both SNP and IAA under NaCl stress. This enhanced antioxidant system and proline accumulation could ameliorate the stress induced by NaCl in plants that was reflected by the improved plant biomass, and photosynthetic efficiency in comparison to control plants.

The objective of the study was to explore the effect of zinc oxide nanoparticles (ZnO-NPs) through root treatment on growth biomarkers, photosynthetic traits, activities of carbonic anhydrase and various antioxidant enzymes as well as the yield of tomato plants. 20 days old seedlings of tomato (cv. PKM-1) were dipped in double distilled water (control), 10, 50, 100 or 200 ppm of ZnO-NPs for 15, 30 or 45 min, respectively. At the stage of 45 and 60 days after sowing (DAS), the plants developed from ZnO-NPs (10 ppm for 30 min) showed improved growth and photosynthetic attributes, enhanced activity of various antioxidant enzymes (e.g., catalase, peroxidase and superoxide dismutase) and higher accumulation of proline and protein content over the non-treated plant. The fruits number and yield in ZnO-NPs treated plants (10 ppm; 30 min) were higher whereas ascorbic acid was lower than the non-treated plant. These fruits possessed higher levels of β-carotene and lycopene content. The root dipping with 10 ppm for 30 min of ZnO-NPs was found to be best for most of the evaluated parameters.

The aim of current investigation was to perform proteomics and physio-chemical studies to dissect the changes in contrasting varieties (S-22 and PKM-1) of Lycopersicon esculentum under low-temperature stress. Plant grown under variable low-temperature stress were analysed for their growth biomarkers, antioxidant enzyme activities, and other physiological parameters, which headed toward the determination of protein species responding to low-temperature and 24-epibrassinolide (EBL) concentrations. The plants grown under temperatures, 20/14, 12/7, and 10/3 °C recorded significantly lower growth biomarkers, SPAD chlorophyll, net photosynthetic rate and carbonic anhydrase activity in S-22 and PKM-1. Moreover, the combined effect of EBL and hydrogen peroxide (H2O2) significantly improved the parameters mentioned above and consecutively upgraded the different antioxidant enzymes (CAT and SOD) with higher accumulation of proline under stress and stress-free environments. Furthermore, proteomics study revealed that the maximum number of differentially expressed proteins were detected in S-22 (EBL + H2O2); while treatment with EBL + H2O2 + low temperature lost expression of 20 proteins. Overall, three proteins (O80577, Q9FJQ8, and Q9SKL2) took a substantial part in the biosynthesis of citrate cycle pathway and enhanced the growth and photosynthetic efficiency of tomato plants under low-temperature stress.

24-epibrassinolide (EBL) and iron (Fe) individually are well recognized for their significant role in various biological functions of plants but their interactive effect on iron transport, stress biomarkers, photosynthetic and biochemical parameters in Brassica juncea is poorly investigated. Therefore, this study was conducted to reveal the effect of Fe in the presence of 24-epibrassinolide (EBL), an analogue of brassinosteroids (BRs) on Brassica juncea plants. Fe in the form Fe-EDTA (1, 5 or 50 µM) was supplied with nutrient solution for 5 days followed by the foliar spray with deionised water (control) or EBL (0.01 µM) on 16-day-old plants for 5 days. Plant samples of 30-day-old plants were collected for the assessment of growth and photosynthetic performance and antioxidant parameters. Results clearly indicated that Fe altered plant metabolism. Lower concentration of Fe (5 µM) increased the growth biomarkers, SPAD (soil plant analysis development) chlorophyll level and photosynthetic rate, whereas higher concentration of Fe (50 µM) proved toxic to Brassica juncea and showed reduced growth, biomass of plant, SPAD chlorophyll level, and photosynthetic traits. However, the application of EBL to Fe-stressed plants reversed the deleterious effects caused by the Fe (50 µM) by improving the activities of antioxidant enzymes and increasing the proline accumulation in plant cells that are reflected in increased plant growth and other physiological parameters. It is concluded that lower concentration of Fe could be exploited as micronutrients whereas combined application of Fe with EBL acts as a stress alleviator for the toxic effects caused by Fe alone.

Glucose is recognized as signaling molecule that regulates growth and development of plants under various environmental cues, but their effect in regulation of copper induced toxicity in plants is not yet investigated. This study revealed the effect of exogenously sourced glucose on Cucumber plants exposed to increasing concentration of copper. Glucose mediated response on growth performance, photosynthetic efficiency, antioxidant enzymes, oxidative stress markers, ion uptake were analyzed in the presence and absence of copper. Glucose alone and in combination with lower concentration of copper improved the growth, photosynthetic performance, and antioxidant capacity of cucumber plants. However, higher concentrations of copper alone showed oxidative damage through increased electrolyte leakage, H2O2 accumulation, lipid peroxidation and reduced uptake of macronutrients. Application of glucose to copper-stressed plants enhanced activities of Rubisco, antioxidant enzymes, proline accumulation and maintained copper level in aerial parts of plants. These enhanced activities of antioxidant enzymes, proline accumulation, uptake of NPK and maintained equilibrium of copper in plants, leading to detoxification of copper stress in cucumber plants. This study provides an understanding that exogenous application of glucose can be employed as vital biochemical approach in alleviating copper-induced toxicity and could be utilized as phytoremediation technique for removal of excess transition metal from polluted soil.

The contribution of nanoparticles (NPs) in physiology of the plants became the new area of interest for the physiologists; as it is very much cost effective compared to the phytohormones. Our present investigation was also based on this interest in which the same doses (50 mg/L) of four different NPs were sprayed on stressed and non-stressed foliage. The experiment was conducted to assess the impact of four NPs viz., zinc oxide (ZnO), silicon dioxide (SiO2), titanium dioxide (TiO2), and ferric oxide (Fe2O3) on the morphology and physiology of linseed in the presence of sodium chloride (NaCl). Plants responded positively to all the treated NPs and improved the growth, carbon and nutrient assimilation, while salt stress increased the content of proline, hydrogen peroxide and superoxide anion. Application of NPs over the stressed plants further increased the antioxidant enzymatic system and other physiochemical reactions. Results indicate that application of NPs increased the growth and physiology of the plant and also increased the salt tolerance capacity of the plant.

Silicon (Si) and 24-Epibrassinolide (EBL) were exogenously applied to assess the photosynthetic efficiency in Brassica juncea under salt stress and to correlate it with the antioxidant system. Seeds of B. juncea were sown in pots and supplemented with NaCl at 15-day stage. Si and EBL treatments were given at 20 and 25-day stage, respectively. Net photosynthetic rate and stomatal conductance reduced significantly in the presence of NaCl. The spray of Si and EBL alone or in combination significantly increased the growth and photosynthetic traits in the presence/absence of NaCl stress. The antioxidant activity (catalase, peroxidase and superoxide dismutase) and proline content got enhanced by salt stress which was further enhanced upon follow-up treatment with 24-epibrassinolide and silicon alone or in combination. A combined effect of Si and EBL counters the damaged caused by the salt stress.

The present experiment was conducted to investigate the promotive effects of exogenous glucose (Glc) on the morpho-physiology in Brassica juncea. L. cv. RGN-48. The plants were treated with the different concentrations (0, 2, 4, and 8%) of glucose as foliar spray at 25 days after sowing (DAS) for 5 days consecutively. The plants were collected to analyze various growth and photosynthetic parameters at 30, 45, and 60 DAS. After 5 days exposure to Glc, the level of carbohydrate, total reducing sugars, proline, plant water status, chlorophyll content, as well as that of activities of peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6), and superoxide dismutase (EC 1.15.1.1) were increased. Glc application also enhanced the gaseous exchange parameters, i.e., stomatal conductance (gs), internal CO2 concentration (Ci), transpiration rate (E), and net photosynthetic rate (PN) in intact leaf. Other enzymes, such as nitrate reductase (EC 1.7.99.4) and carbonic anhydrase (EC 4.2.1.1) were also increased. Additionally, microscopic studies further reveal a remarkable increase in the stomatal aperture on Glc exposure. Moreover, exogenous Glc decreases the levels of malondialdehyde (MDA), superoxide radical (O2·−) and hydrogen peroxide (H2O2). This indicates that exogenous Glc application has a positive effect on Brassica juncea plants.

The present study was carried out to assess the role of zinc oxide nanoparticles (ZnO-NPs) in tomato plants on growth, photosynthetic efficiency, and antioxidant system. At 20-d stage of growth, roots of tomato plants were dipped into 0, 2, 4, 8, or 16 mg(ZnO-NPs) L–1 for 15, 30, and 45 min and then seedlings were transplanted in their respective cups and allowed to grow under natural environmental conditions. At 45-d stage of growth, the ZnO-NPs treatments significantly increased growth, photosynthetic efficiency together with activities of carbonic anhydrase and antioxidant systems in a concentration- and duration-dependent manner. Moreover, the treatment by 8 mg(ZnO-NPs) L–1 for 30 min proved to be the most effective and resulted in maximum activities of antioxidant enzymes, proline accumulation and the photosynthetic rate. We concluded that presence of ZnO-NPs improved the antioxidant systems and speeded up proline accumulation that could provide stability to plants and improved photosynthetic efficiency.

This study was conducted to unravel the EBL mediated changes on the enzymes of proline metabolism under combined stress of aluminum and salt through varied mode of application. The results of the study revealed that application of EBL through different mode significantly increased the activities of P5CS and δ-OAT, proline content, photosynthetic efficiency and various enzymes of antioxidant system whereas, these parameters were further accelerated in the plants exposed to combined stress of aluminum and salt followed by EBL treatment. These findings indicate that exogenous application of EBL modified the activity of enzymes of proline metabolism and also scavenges the excess reactive oxygen species through improved activities of antioxidant enzymes which could have provided the ability to confer tolerance in wheat plants under combination of aluminum and salt stress.

The present study was carried out to screen out the best concentration of proline, applied exogenously as foliar spray, which will have beneficial effects on growth and physio-biochemical parameters in two varieties of Brassica juncea (‘Varuna’ and ‘RH-30’). The proline concentrations tested in this experiment were 0, 10, 20 or 30 mM. The foliar spray was done at 29 days after sowing (DAS) and sampling at 60 DAS. Out of these concentrations, 20 mM proline was found best. The proline treatment significantly increased the growth, net photosynthetic rate and related attributes, SPAD value of chlorophyll, leaf carbonic anhydrase activity and quantum yield of photosystem II, as well as proline content and activity of antioxident enzymes also increased in both the varieties at 60 d stage of growth. The result was more pronounced in the ‘Varuna’ than in ‘RH-30’.

The present investigation was conducted to evaluate the silicon (Si) mediated responses in different cultivars of Indian mustard (Brassica juncea) and to evaluate if Si could be used as an essential, beneficial, or quasi-essential element for growth and development of these cultivars. Surface sterilized seeds were sown in pots and allowed to germinate under natural environmental conditions. At 10, 12, 14, 16, and 18 days after germination, a range of Si concentrations (0.0, 0.2, 0.4, 0.8 and 1.6 mM) was administered to the soil and at 30 days post germination the plants were sampled to assess growth and development, leaf gas exchange traits and plant biochemical parameters, including activities of carbonic anhydrase, catalase, peroxidase, superoxide dismutase, and protein and proline content. The results demonstrate a dual response to Si concentration: 0.8 mM of Si significantly increased plant growth and development (length of root and shoot, fresh and dry biomass, and leaf area) and photosynthetic efficiency, and enhanced the antioxidant response in T-59 over all the other cultivars tested, whereas, 1.6 mM of Si significantly reduced the above parameters. It is therefore concluded that low levels of Si could be used as a quasi-essential element for enhanced photosynthetic efficiency and antioxidant response ofBrassica junceaplants; however, the response is cultivar specific and concentration dependent.

The effects of foliar application of proline (20 mM) on growth, physio-biochemical, and yield parameters were assessed in two Brassica juncea (L.) Czern & Coss cultivars, namely, Varuna and RH-30, at different levels (2.8, 4.2, or 5.6 dsm(-1)) of NaCl in soil. At 29 days after sowing (DAS), plants were sprayed with either 20 mM proline or water in the presence or absence of NaCl stress. The NaCl negatively affected parameters related to growth, photosynthesis, and yield in both varieties but more in RH-30 than in Varuna. Exogenous application of proline counteracted the effects of salt stress in Varuna only, by increasing the antioxidative capacity of the plants. Moreover, proline was not effective in alleviating the detrimental effects of higher salt concentrations on the studied parameters. Proline application to unstressed plants increased growth, photosynthesis, and yield parameters in both varieties; however, the effects were more prominent in Varuna than in RH-30.

Soil salinity is one of the major abiotic stress factors that hampers plant growth and productivity by limiting photosynthesis and other related metabolic processes. In this study we investigated whether treatment with proline and/or 24-epibrassinolide (EBL) to two contrasting cultivars of Brassica juncea (L.) Czern and Coss viz. Varuna and RH-30 could counteract with the adverse effects of salinity on photosynthesis and seed yield. Plants were treated with proline and/or 24-epibrassinolide (EBL) at 28 and 29d-stages of growth. Salt stress reduced plant growth, photosynthetic attributes, efficiency of PSII (Fv/Fm), leaf water potential and finally seed yield, at harvest but improved the activity of antioxidant enzymes in both the cultivars in a concentration dependent manner. Exogenous application of EBL with proline completely neutralised the adverse effects of salt at 78 mM or 117 mM stress levels whereas the treatment partially neutralised the impact of highest salt concentration of 156 mM, through the upregulation of the antioxidant system.

Cadmium, a non-essential and toxic metal, negatively affects plant growth and productivity, and alters the plant’s physiological processes necessary for its survival. The present study was designed to explore the individual and combined effects of calcium and salicylic acid (SA) on the morphology and physiology of Brassica juncea L. cv. Varuna under cadmium stress. The application of calcium (2 mM) through the soil and/or SA (10-5 M) as foliar spray enhanced the growth, photosynthetic parameters, and proline content determined after 45 days of treatment. The application of cadmium (6 mg kg-1) through the soil was toxic and decreased both growth and the photosynthetic parameters. The application of calcium and SA in combination was most effective in alleviating the harmful effects of cadmium on growth and photosynthesis. Calcium and SA clearly induced plant protection mechanisms by enhancing proline and chlorophyll accumulation in the leaves.

Increasing contamination and higher enrichment ratio of non-essential heavy metal cadmium (Cd) induce various toxic responses in plants when accumulated above the threshold level. These effects and growth responses are genotype and Cd level dependent. An experiment was conducted to analyze the effect of Cd toxicity in Brassica juncea [L] Czern and Coss by selecting its two varieties Varuna and RH-30. Cadmium (0, 25, 50 or 100mg CdCl2kg−1 of soil) fed to soil decreased the values of growth characteristics, activity of nitrate reductase and leaf water potential, whereas activities of antioxidant enzymes and proline content increased with the increasing concentration of Cd, observed at 30 and 60day stages of growth, in both the varieties. Moreover, Cd uptake by the roots was higher in RH-30 than Varuna. Also the activity of antioxidant enzymes and proline accumulation were higher in Varuna with increasing soil level of Cd. Out of the two varieties, Varuna was more tolerant than RH-30 to Cd stress.

This study examines the impact of 28-homobrassinolide (HBL) in alleviating the effects of cadmium (Cd) and salinity (NaCl) on wheat plants solely and against the synergy. The surface sterilized seeds of Triticum aestivum cv. PBW-373 were sown in the soil amended either with salinity or cadmium or both. The foliage in was sprayed at 20d after sowing (DAS) both in stressed and non-stressed plants. The spray of HBL at 20 DAS increased almost all the parameters while decreased the H2O2 content and lipid peroxidation in the leaves. The presence of cadmium and/or salinity decreased the values for all the growth and photosynthetic parameters but improved the activity of antioxidant enzymes and proline content in 30d old plants. However, the ill effects observed under NaCl and/or Cd treatment were completely overcomed by the spray of HBL to the plants at 20d stage. The spray of HBL to stressed plants further increased the antioxidant enzyme activities and proline content thereby giving tolerance to the plants against the stress.

Cowpea (Vigna unguiculata L.) is an important legume well grown in semiarid and arid environment. Hydrogen peroxide solutions (0.1, 0.5, 1.0, and 1.5 mM) have been used to optimize growth and photosynthetic performance of cowpea plant at two growth stages [30 and 45 DAS (days of sowing)]. Foliar application of H2O2 at 0.5 > 1.0 mM solution at 29 DAS optimally promoted the photosynthetic attributes [leaf chlorophyll content, net photosynthetic rate (PN), water use efficiency, and maximum quantum yield of PSII (Fv/Fm)] and growth performance [root and shoot length; fresh and dry weight] of plants where the responses were more significant at the later growth stage. It was favored by activity of enzymes as carbonic anhydrase [CA; E.C. 4.2.1.1] and nitrate reductase [NR, E.C. 1.6.6.1] and those of antioxidant enzymes viz. peroxidase [POX; EC 1.11.1.7], catalase [CAT; EC 1.11.1.6], and superoxide dismutase [SOD; EC 1.15.1.1] and leaf proline content. Strengthened root system and antioxidant activity, particularly leaf proline level appeared to be the key factor for efficient photosynthesis and growth responses.

Seeds of chickpea were sown in the pots supplemented with 0, 25, 50 or 100 mg of cadmium per kg of soil. At the stage of 30 days after sowing (DAS), the raised plants were sprayed with 20 mM proline except for the control plants which received double distilled water (DDW). The increasing degree of damage caused by the increasing concentration of Cd in soil was partially overcome by proline application. The treatment of 25 mg Cd fed plants with 20 mM proline increased significantly the nodulation parameters, leghemoglobin and carbohydrate content, leaf nitrogen and root nitrate content, activity of enzymes nitrogenase (E.C 1.18.6.1), nitrate reductase (E.C. 1.6.6.1), glutamine synthetase (GS) (E.C 6.3.1.2), glutamate synthase (GOGAT) (E.C 1.4.7.1) and glutamate dehydrogenase (GDH) (E.C 1.4.1.3) over that of the control. The value of these parameters was found to be at par with that of the control in the plants exposed to 50 mg Cd per kg of soil and also treated with 20 mM proline. However, the treatment was not found to be effective in alleviating the adverse effects of 100 mg Cd per kg of soil.

The present study was carried out to elucidate the protective role of sodium nitroprusside (SNP) against salt (NaCl) stress given as seed soaking in tomato (Solanum lycopersicum Mill. cv. K-21). For this experiment prior to sowing, the surface sterilized tomato seeds were soaked in different concentrations of NaCl solution (50, 100, and 150 mM) for 8 hours. Some NaCl soaked seeds were then transferred to the 10−5 M of SNP solution for 8 hours. The plants were sampled at 60 DAS to assess the nitrate reductase activity, proline content and the activities of antioxidant enzymes. The antioxidant enzyme activity and proline content increased in the plants where SNP was applied as a follow up treatment of the NaCl as seed soaking over the control plants thereby providing stress tolerance to the plants. In case of the nitrate reductase activity the toxic effects generated by the lowest concentration of NaCl (50 mM) was completely neutralized by SNP and partly at higher concentrations (100/150 mM). These results suggest that nitric oxide can be used as a stress alleviator in plants which are grown in the soil contaminated with salinity stress.

When exposed to stressful conditions, plants accumulate an array of metabolites, particularly amino acids. Amino acids have traditionally been considered as precursors to and constituents of proteins, and play an important role in plant metabolism and development. A large body of data suggests a positive correlation between proline accumulation and plant stress. Proline, an amino acid, plays a highly beneficial role in plants exposed to various stress conditions. Besides acting as an excellent osmolyte, proline plays three major roles during stress, i.e., as a metal chelator, an antioxidative defense molecule and a signaling molecule. Review of the literature indicates that a stressful environment results in an overproduction of proline in plants which in turn imparts stress tolerance by maintaining cell turgor or osmotic balance; stabilizing membranes thereby preventing electrolyte leakage; and bringing concentrations of reactive oxygen species (ROS) within normal ranges, thus preventing oxidative burst in plants. Reports indicate enhanced stress tolerance when proline is supplied exogenously at low concentrations. However, some reports indicate toxic effects of proline when supplied exogenously at higher concentrations. In this article, we review and discuss the effects of exogenous proline on plants exposed to various abiotic stresses. Numerous examples of successful application of exogenous proline to improve stress tolerance are presented. The roles played by exogenous proline under varying environments have been critically examined and reviewed.

Brassinosteroids (BRs) are a class of polyhydroxysteroid plant hormones. The sensitivity of a crop to abiotic/biotic stress is a functional aspect of its response as regulated by the efficient internal buildup of hormones like BRs. A better understanding of how the brassinosteroid isomers differentially affect plant responses in tomato (Solanum lycopersicum L.) is necessary to improve production. Plants of cv. K-21 were grown in a net house and foliage was treated with brassinosteroid isomers 28-homobrassinolide (HBL) and 24-epibrassinolide (EBL) at concentrations of 10−6, 10−8, or 10−10 M. Plants responded more to EBL than to HBL. All treatments increased nitrate reductase activity and the antioxidant system with respect to the control. However, the 10−8 M concentration of EBL produced higher nitrate reductase activity and better stimulated the antioxidant system in tomato. In physiological experiments, different concentrations/modes of stress/hormone(s) were tested and justified in biosynthetic or signa...

The present study was conducted with an aim to gain better insight of brassinosteroid generated response on the effects of cadmium on photosynthetic machinery and active oxygen metabolism in two tomato cultivars (K-25 and Sarvodya). These tomato cultivars were subjected to graded cadmium levels in soil (0, 3, 6, 9 or 12 mg kg(-1) soil) with their foliage being sprayed with 0 or 10(-8) M of 28-homobrassinolide/24-epibrassinolide (HBL/EBL) at 59 d stage. The results suggested that photosynthetic parameters, leaf water potential and activity of several enzymes (nitrate reductase and carbonic anhydrase) decreased significantly in both the cultivars, to a lesser extent in K-25 than Sarvodya with the increasing levels of cadmium in the soil. However, the activity of antioxidant enzymes and proline content increased in response to metal treatment as well as the application of brassinosteroids (HBL/EBL). Overall, exogenous application of brassinosteroids improved the activity of photosynthetic machinery and that of antioxidant defense system in both the cultivars, and also nullified the damaging effect of metal on these parameters.

The present experiment was conducted to evaluate salt tolerance in varieties of Indian mustard (Brassica juncea). Sterilized seeds were grown under natural environment in pots containing soil amended with 1.4 (control), 2.8, 4.2 and 5.6 dSm−1 NaCl and sampled at 30 days after sowing. Growth was recorded in terms of length, fresh mass, dry mass and leaf area of plants, which was drastically reduced in Chapka Rohini, while there was little effect of NaCl treatment on Varuna. In Chapka Rohini, a rise in the level of proline was observed which followed the decline in protein content. The declines in net photosynthesis and other related parameters have been attributed to this decline. From the results, it could be suggested that Varuna is salt-tolerant while Chapka Rohini is the salt-sensitive variety of mustard among the screened genotypes. Photosynthetic capacity is a major factor in conferring the salt-sensitiveness and tolerance in plant varieties.

Surface-sterilized seeds of two tomato cultivars (cv. K-25 and Sarvodya) were soaked in 100 microM CdCl(2) for 8 h (shotgun approach). The resulting 59-day-old seedlings were sprayed with 10(-8) M of 28-homobrassinolide (HBL) or 24-epibrassinolide (EBL) to their foliage. Both cultivars showed significantly different response to Cd stress. Cadmium severely restricted the growth, photosynthetic efficiency, and activity of nitrate reductase (E.C. 1.6.6.1) and carbonic anhydrase (E.C. 4.2.1.1) in Sarvodya as compared to K-25. However, the activities of antioxidative enzymes were significantly higher in K-25. This result may be considered an indication of better tolerance of the K-25 cultivars to Cd stress. Moreover, the spray of both the brassinosteroids (HBL/EBL) were found very effective in neutralizing the adverse effects generated by metals that reflect in better photosynthetic performance by the cultivars. An interesting aspect of this study is that HBL or EBL spray caused a further increase in proline content and antioxidative enzyme activities, which were already enhanced by Cd stress. This effect of brassinosteroids (HBL/EBL) was more pronounced in K-25 than in Sarvodya, representing the tolerance and adoptable behavior of K-25.

A sand culture experiment was conducted to study ameliorative role of 28-homobrassinolide (HBL) in Brassica juncea seedlings raised from the seeds treated with water, or 10 −10 , 10 −8 and 10 −6 M 28-homobrassinolide (HBL) and grown in the presence of copper (50, 100 and 150 mg kg −1 sand) and sampled at 30 days after sowing. The plants grown in the presence of copper exhibited a significant decline in growth, chlorophyll and photosynthetic parameters. However, the activity of antioxidant enzymes: catalase (E.C. 1.11.1.6), peroxidase (E.C. 1.11.1.7) and superoxide dismutase (E.C. 1.15.1.1) and the content of proline increased in the plants grown under copper stress and/or raised from treatment with HBL. However, H 2 O 2 content increased significantly in copper-treated plants and decreased in plants given HBL treatment. Treatment of seeds with HBL improved the growth, photosynthetic parameters and antioxidant enzymes and also improved in the plants grown under copper stress. The elevated antioxidant enzyme and proline might be responsible to overcome the toxic effects of copper in B. juncea .

To investigate the effect of exogenously applied 28-homobrassinolide (HBL) on drought-stressed plants, photosynthesis and antioxidant systems were examined in Indian mustard (Brassica juncea L.). Seedlings of Indian mustard were subjected to drought stress for 7 days at the 8–14 (DS1)/15–21 (DS2) days’ stage of growth and then returned to normal conditions of growth. These seedlings were sprayed with HBL (0.01 μM) at the 30-day stage and were sampled at 60 days to assess the changes in growth, photosynthesis and antioxidant enzymes. Plants exposed to stress at either of the stages of growth exhibited a significant decrease in growth and photosynthesis. The exposure of plants to stress at an earlier stage (DS1) was more inhibitory than that at a later stage (DS2). However, the follow-up treatment with HBL significantly improved the values of these parameters and also overcame the inhibitory effect of water stress. The activity of antioxidant enzymes [catalase (E.C. 1.11.1.6), peroxidase (E.C. 1.11.1.7) and superoxide dismutase (E.C. 1.15.1.1)] and proline content in leaves exhibited an increase in response to both the treatment factors, where their interaction had an additive effect. It was, therefore, concluded that the elevated antioxidant system, at least in part, was responsible for amelioration of the drought stress.

Pots holding 7 day-old seedlings of Indian mustard (Brassica juncea L.) were subjected to differential temperature stress by exposing plants to 30 or 40ºC for 24 h. Seedlings were sprayed with double distilled water (DDW) or 10-5M salicylic acid (SA) at the 8-day stage and were sampled at 30 DAS. The plants exposed to temperature stress exhibited a significant (p < 0.05) decline in growth, and in levels of chlorophyll, nitrate reductase and carbonic anhydrase activities and photosynthetic parameters. A follow-up treatment with SA protected against the stress generated by temperature and significantly improved the above parameters. Antioxidative enzymes and levels of proline significantly increased in response to SA as well as to temperature stress.

Plants of Lycopersicon esculentum L. cv. K-25 were subjected to water stress by withholding water for 10 days at 20 (WS I) and 30 (WS II) days after sowing (DAS). Seedlings were sprayed with double distilled water (DDW) or 10−5M salicylic acid (SA) at 45 DAS. The water stress at earlier stage of growth (20 day stage) was more inhibitory as compared to the later stage (30 day stage). The plants exposed to water stress exhibited a significant (p

Brassinosteroids (BRs) elicit diverse physiological responses and ameliorate various biotic and abiotic stresses. With an aim to further explore and elaborate their role in plants subjected to abiotic stress, more specifically the heavy metal stress, the seedlings of mung bean were grown in a plant growth chamber under controlled conditions, on a sandy substratum. The seedlings were subjected to aluminium (0.0, 1.0 or 10.0 mM) stress, at 1-week-old stage and were sprayed with 0 or 10−8 M of 24-epibrassinolide (EBL) or 28-homobrassinolide (HBL) at 14-day stage. The analysis of the plants at the completion of 3 weeks of growth revealed that the presence of aluminium in the nutrient medium caused a sharp reduction in growth (length, fresh and dry mass of root and shoot), the activity of carbonic anhydrase (E.C. 4.2.1.1), relative water content, water use efficiency, chlorophyll content and the rate of photosynthesis. However, the activity of antioxidative enzymes [catalase (E.C. 1.11.1.6), peroxidase (E.C. 1.11.1.7) and superoxide dismutase (E.C. 1.15.1.1)] in leaves and the content of proline, both in leaves and roots increased in the aluminium-stressed plants. The spray of EBL or HBL, in absence of aluminium strongly favoured the above parameters and also improved them, in the plants grown under aluminium stress. Moreover, it is also noteworthy that EBL and HBL caused a further stimulation of antioxidative enzymes and proline content, which were already enhanced by aluminium stress. This led us to the conclusion that the elevated level of proline in association with antioxidant system, at least in part, was responsible for the amelioration of Al stress in mung bean seedlings.

The response of chickpea ( Cicer arietinum L.) cv. KPG-59 to pre-sowing seed treatment with 28-homobrassinolide (HBR) and/or sodium chloride (NaCl) was investigated. The seeds imbibed in aqueous solution of 10 −10 or 10 −8 M of HBR for 8 h, resulted in an increase in the values for most of the characteristics of shoot and root at 90-day stage and seed yield, at harvest. The plants resulting from the seeds soaked in HBR (10 −8 M) possessed 23% and 31% higher leaf nitrate reductase (E.C. 1.6.6.1) and carbonic anhydrase (E.C. 4.2.2.1) activities, 34% more dry mass, 30% higher nodule number, 31% and 18% more nodule fresh and dry mass, compared with water soaked, control. Leghaemoglobin content and nitrogenase activity (E.C. 1.7.99.2) were 28% and 30% higher while nodule nitrogen and carbohydrate contents decreased by 5% and 6%, compared with the control. Moreover, seed yield increased by 26% over the control, at harvest. The values for all the above characteristics declined significantly, in the plants raised from the seeds soaked in NaCl. However, this ill effect was overcome, if NaCl treatment was given before or after HBR treatment.

Plants of Brassica juncea L. cv. T-59 were supplied with 50 or 100 µM nickel (Ni50, Ni100) at 10 d after sowing (DAS), and sprayed with 28-homobrassinolide (HBR) at 20 DAS. The plants treated with Ni alone exhibited reduced growth, net photosynthetic rate, content of chlorophyll, and the activities of nitrate reductase (E.C.1.6.6.1) and carbonic anhydrase (E.C. 4.2.1.1) at observed 40 DAS, whereas, the contents of peroxidase (PER), catalase (CAT), and proline were increased. However, the spray of HBR partially neutralized the toxic effect of Ni on most of the parameters. Moreover, the treatment of HBR in association with either of the Ni concentration boosted the contents of PER and CAT in leaves and that of proline both in leaves and roots.

Seeds of chickpea inoculated with Rhizobium were sown in pots supplemented with different doses of cadmium (0, 25, 50 or 100 mg per kg of soil). At the stage of 30 days after sowing (DAS), the plants were sprayed with 20 mM solution of proline and were sampled at 90 DAS to assess the various parameters. The foliar treatment of proline resulted in the alleviation of the adverse effects generated by metal exposure, which was expressed in terms of the increase in plant growth. The activity of carbonic anhydrase in the cadmium-fed plants sprayed with proline was higher than that of control. The proline applied as foliar spray increased the photosynthetic attributes and yield characteristics in the cadmium-stressed plants. The activity of antioxidative enzymes increased with increasing concentration of cadmium. Maximum values were recorded in the plants exposed to 100 mg cadmium per kg of soil.

Among various environmental stresses, salt stress is extensively damaging to major crops all over the world. An experiment was conducted to explore the role of exogenously applied 28 homobrassinolide (HBL) and salicylic acid (SA) on growth, photosynthetic parameters, transpiration and proline content of Brassica juncea L. cultivar Varuna in presence or absence of saline conditions (4.2 dsm −1 ). The leaves of 29d old plants were sprayed with distilled water, HBL and/or SA and plant responses were studied at 30 days after sowing (24 h after spray) and 45 days after sowing. The salinity significantly reduced the plant growth, gas exchange parameters but increased proline content and electrolyte leakage in the leaves. The effects were more pronounced at 30 DAS than 45 DAS. Out of the two hormones (HBL/SA) HBL excelled in its effects at both sampling stages. Toxic effects generated by salinity stress were completely overcome by the combination of the two hormones (HBL and SA) at 45 DAS.

Cobalt (Co) affords both beneficial as well as toxic effects to plants. The present study was performed with an aim to find out the varietal differences among five tomato cultivars against the Co induced changes in growth, photosynthesis, nitrate reductase (E.C.1.6.6.1), carbonic anhydrase (E.C.4.2.1.1), antioxidative enzymes i.e. peroxidase (E.C.1.11.1.7), catalase (E.C.1.11.1.6), superoxide dismutase (E.C.1.15.1.1) and that of proline content. Seeds of tomato (varieties, K-25, NTS-9, NBR-Uday, Sarvodya, and Malti) were soaked in 0, 100, 200 or 300 µM CoCl2 for 0, 4, 8, 12 h (shotgun approach) and sampled at 30 days after sowing. All the varieties showed significantly different response to different treatment combinations. Despite substantial varietal difference, increased Co concentration caused concomitant decrease in growth, photosynthesis and the activity of nitrate reductase and carbonic anhydrase. However, the activity of antioxidant enzymes and that of proline content increased with the increased concentration of Co as well as duration of soaking in all the varieties. Out of the varieties, K-25 possessed maximum antioxidative enzyme and proline content that represent its most resistant nature against the toxic effect of Co. The order of susceptibility/sensitivity was K-25 > NTS-9 > NBR-Uday > Sarvodya > Malti.

The present paper deals with the effect of exogenous application of proline as a shotgun approach on growth, photosynthesis, and antioxidative system in 25-day-old plants of two different cultivars of Brassica juncea L. (Varuna and RH-30) under natural conditions. Exogenous application of proline significantly increased plant growth, photosynthetic rate, and the activities of antioxidant enzymes, compared with untreated seedlings. Pre-sowing seed soaking in 20 mM proline, for 8 h, proved best among all the other concentrations used.

Seeds of five wheat (Triticum aestivum) cultivars (PBW-373, UP-2338, DL-LOK-01, DL-373, and HD-2338) were sown in earthen pots and 10-day-old seedlings were exposed to 0, 50, and 100 μM of nickel (Ni) in the form of nickel chloride. At the 20-day stage, seedlings were sprayed with 0.01 μM of 28-homobrassinolide (HBL). The results of the experiment at the 30-day stage revealed a decline in the dry mass per plant, leaf area, leaf water potential, and net photosynthetic rate with concomitant decline in the activities of various enzymes (viz. carbonic anhydrase and nitrate reductase) with an increasing concentration of Ni. However, an increase in proline content and the activities of catalase, peroxidase, and superoxide dismutase was observed as a result of an increase in Ni concentration. Moreover, the treatment of these stressed plants with HBL enhanced the activities of carbonic anhydrase and nitrate reductase, catalase, peroxidase, and superoxide dismutase. The proline content in the leaves also increased, which is known to act as an osmolyte and reactive oxygen species scavenger. The toxic effects generated by Ni were ameliorated by HBL through an improved antioxidant system and osmolyte. Moreover, improvement of photosynthetic parameters and growth characteristics further strengthen our belief that HBL acted as a potent stress alleviator.

Seeds of Indian mustard (Brassica juncea (L.) Czern. et Coss.) were exposed to 0, 50, 100 and 150 mmol/L NaCl for 8 h and seeds were sown in an earthen pot. These stressed seedlings were subsequently sprayed with 10 micromol/L salicylic acid (SA) at 30 d and were sampled at 60 d to assess the changes in growth, photosynthesis and antioxidant enzymes. The seedlings raised from the seeds treated with NaCl had significantly reduced growth and the activities of carbonic anhydrase, nitrate reductase and photosynthesis, and the decrease was proportional to the increase in NaCl concentration. However, the antioxidant enzymes (catalase, peroxidase and superoxide dismutase) and proline content was enhanced in response to NaCl and/or SA treatment, where their interaction had an additive effect. Moreover, the toxic effects generated by the lower concentration of NaCl (50 mmol/L) were completely overcome by the application of SA. It was, therefore, concluded that SA ameliorated the stress generated by NaCl through the alleviated antioxidant system.

The plants of Brassica juncea (L) were grown in the presence of NaCl and/or NiCl 2 and were sprayed with 1 μM of 24-epibrassinolide (EBL) at 15 days after sowing (DAS) and were sampled at 30 DAS. The plants exposed to NaCl and/or NiCl 2 exhibited a significant decline in growth, the level of pigments and photosynthetic parameters. However, the follow up treatment with EBL detoxified the stress generated by NaCl and/or NiCl 2 and significantly improved the above parameters. The NaCl and/or NiCl 2 increased electrolyte leakage and lipid peroxidation, and decreased the membrane stability index (MSI) and relative water content. However, the EBL treatment in absence of the stress improved the MSI and relative water content but could not influence electrolyte leakage and lipid peroxidation. The antioxidative enzymes and the level of proline exhibited a significant increase in response to EBL as well as to NaCl and/or NiCl 2 stress.

An experiment was conducted to examine the extent of low-temperature stress during early seed germination and to investigate the mitigating effects of brassinosteroids. Sterilized Cicer arietinum seeds were soaked in distilled water for 24 h then placed in three sets of cotton-lined petri dishes. These three sets of seeds were exposed to different temperatures: 25°C (control), 0°C and -10°C. Another experiment was conducted using the same set of conditions but included a 24 h soaking step in 28-homobrassinolide (HBL) under controlled conditions. The seedlings were evaluated after 72 h. The results clearly indicated that seed germination, the activities of nitrate reductase and carbonic anhydrase, the accumulated levels of proline and protein decreased in response to low-temperature stress. HBL partially ameliorated the stress at 0°C but failed to overcome the -10°C stress. Based on our observations, it could be concluded that brassinosteroids could partially overcome the stress generated by 0°C during the seed germination stage but could not overcome the stress generated by -10°C.

The present study was carried out to examine salt-induced modulation in growth, photosynthetic characteristics and antioxidant system in two cultivars of Brassica juncea Czern and Coss varieties (Varuna and RH-30). The surface sterilized seeds of these varieties were sown in the soil amended with different levels (2.8, 4.2 or 5.6 dsm(-1)) of sodium chloride under a simple randomized block design. The salt treatment significantly decreased growth, net photosynthetic rate and its related attributes, chlorophyll fluorescence, SPAD value of chlorophyll, leaf carbonic anhydrase activity and leaf water potential, whereas electrolyte leakage, proline content, and activity of catalase, peroxidase and superoxide dismutase enzymes increased in both the varieties at 30 d stage of growth. The variety Varuna was found more resistant than RH-30 to the salt stress and possessed higher values for growth, photosynthetic attributes and antioxidant enzymes. Out of the graded concentrations (2.8, 4.2 or 5.6 dsm(-1)) of sodium chloride, 2.8 sm(-1) was least toxic and 5.6 dsm(-1) was most harmful. The variation in the responses of these two varieties to salt stress is attributed to their differential photosynthetic traits, SPAD chlorophyll value and antioxidant capacity, which can be used as potential markers for screening mustard plants for salt tolerance.