Abiotic stresses (such as metals/metalloids, salinity, ozone, UV-B radiation, extreme temperatures, and drought) are among the most challenging threats to agricultural system and economic yield of ...crop plants. These stresses (in isolation and/or combination) induce numerous adverse effects in plants, impair biochemical/physiological and molecular processes, and eventually cause severe reductions in plant growth, development and overall productivity. Phytohormones have been recognized as a strong tool for sustainably alleviating adverse effects of abiotic stresses in crop plants. In particular, the significance of salicylic acid (SA) has been increasingly recognized in improved plant abiotic stress-tolerance via SA-mediated control of major plant-metabolic processes. However, the basic biochemical/physiological and molecular mechanisms that potentially underpin SA-induced plant-tolerance to major abiotic stresses remain least discussed. Based on recent reports, this paper: (a) overviews historical background and biosynthesis of SA under both optimal and stressful environments in plants; (b) critically appraises the role of SA in plants exposed to major abiotic stresses;
Proline content and ethylene production have been shown to be involved in salt tolerance mechanisms in plants. To assess the role of nitrogen (N) in the protection of photosynthesis under salt ...stress, the effect of N (0, 5, 10, 20mM) on proline and ethylene was studied in mustard (Brassica juncea). Sufficient N (10mM) optimized proline production under non-saline conditions through an increase in proline-metabolizing enzymes, leading to osmotic balance and protection of photosynthesis through optimal ethylene production. Excess N (20mM), in the absence of salt stress, inhibited photosynthesis and caused higher ethylene evolution but lower proline production compared to sufficient N. In contrast, under salt stress with an increased demand for N, excess N optimized ethylene production, which regulates the proline content resulting in recovered photosynthesis. The effect of excess N on photosynthesis under salt stress was further substantiated by the application of the ethylene biosynthesis inhibitor, 1-aminoethoxy vinylglycine (AVG), which inhibited proline production and photosynthesis. Without salt stress, AVG promoted photosynthesis in plants receiving excess N by inhibiting stress ethylene production. The results suggest that a regulatory interaction exists between ethylene, proline and N for salt tolerance. Nitrogen differentially regulates proline production and ethylene formation to alleviate the adverse effect of salinity on photosynthesis in mustard.
ABSTRACT
Sulphur (S) assimilation leads to the formation of glutathione (GSH) and alleviation of cadmium (Cd) stress. GSH is synthesized from its immediate metabolite cysteine, which also serves as a ...metabolite for ethylene formation through S‐adenosyl methionine. To assess the role of ethylene in S‐induced alleviation of Cd stress on photosynthesis, the effects of S or ethephon (ethylene source) on GSH and ethylene were examined in mustard (Brassica juncea L. cv. Varuna). Sufficient‐S at 100 mg S kg−1 soil alleviated Cd‐induced photosynthetic inhibition more than excess‐S (200 mg S kg−1 soil) via ethylene by increased GSH. Under Cd stress, plants were less sensitive to ethylene, despite high ethylene evolution, and showed photosynthetic inhibition. Ethylene sensitivity of plants increased with ethephon or sufficient‐S, triggering the induction of an antioxidant system, and leading to increased photosynthesis even under Cd stress. The effects of ethephon and S under Cd stress were similar. The effects of S were reversed by ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG), suggesting that ethylene plays an important role in S‐induced alleviation of Cd stress on photosynthesis.
Sulfur (S) alleviates cadmium (Cd)‐induced photosynthetic inhibition by upregulation of glutathione (GSH) synthesis. Ethylene may play a role in S‐mediated alleviation of Cd stress as ethylene and GSH are formed from a common metabolite. Sufficient‐S was found more effective than excess‐S in inducing Cd tolerance and alleviated photosynthetic inhibition through ethylene by maintaining high GSH.
The influence of salicylic acid (SA) in alleviation of salt stress in mungbean (Vigna radiata L.) through modulation of glycinebetaine (GB) and ethylene was studied. SA application at 0.5 mM ...increased methionine (Met) and GB accumulation in plants concomitant with the suppression of ethylene formation by inhibiting 1-aminocyclopropane carboxylic acid synthase (ACS) activity more conspicuously under salt stress than no stress. The increased GB accumulation together with reduced ethylene under salt stress by SA application was associated with increased glutathione (GSH) content and lower oxidative stress. These positive effects on plant metabolism induced by SA application led to improved photosynthesis and growth under salt stress. These results suggest that SA induces GB accumulation through increased Met and suppresses ethylene formation under salt stress and enhances antioxidant system resulting in alleviation of adverse effects of salt stress on photosynthesis and growth. These effects of SA were substantiated by the findings that application of SA-analogue, 2, 6, dichloro-isonicotinic acid (INA) and ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG) resulted in similar effects on Met, GB, ethylene production, photosynthesis and growth under salt stress. Future studies on the interaction between SA, GB and ethylene could be exploited for adaptive responses of plants under salt stress.
•Salicylic acid modulates glycinebetaine and ethylene production.•Salicylic acid regulates ethylene synthesis to increase salt tolerance.•Salicylic acid increases plants' sensitivity to ethylene.•Salicylic acid improves photosynthesis and growth under salt stress.
Major abiotic stress factors such as salt and drought adversely affect important physiological processes and biochemical mechanisms and cause severe loss in crop productivity worldwide. Plants ...develop various strategies to stand healthy against these stress factors. The accumulation of proline (Pro) is one of the striking metabolic responses of plants to salt and drought stress. Pro biosynthesis and signalling contribute to the redox balance of cell under normal and stressful conditions. However, literature is meager on the sustainable strategies potentially fit for modulating Pro biosynthesis and production in stressed plants. Considering the recent literature, this paper in its first part overviews Pro biosynthesis and transport in plants and also briefly highlights the significance of Pro in plant responses to salt and drought stress. Secondly, this paper discusses mechanisms underlying the regulation of Pro metabolism in salt and drought-exposed plant via phytohormones, mineral nutrients and transgenic approaches. The outcome of the studies may give new opportunities in modulating Pro metabolism for improving plant tolerance to salt and drought stress and benefit sustainable agriculture.
•Proline serves as osmoprotectants in plants.•Phytohormones and nutrients play role in modulating proline metabolism.•Proline induces salt and drought tolerance.
The complex juvenile/maturity transition during a plant's life cycle includes growth, reproduction, and senescence of its fundamental organs: leaves, flowers, and fruits. Growth and senescence of ...leaves, flowers, and fruits involve several genetic networks where the phytohormone ethylene plays a key role, together with other hormones, integrating different signals and allowing the onset of conditions favorable for stage progression, reproductive success and organ longevity. Changes in ethylene level, its perception, and the hormonal crosstalk directly or indirectly regulate the lifespan of plants. The present review focused on ethylene's role in the development and senescence processes in leaves, flowers and fruits, paying special attention to the complex networks of ethylene crosstalk with other hormones. Moreover, aspects with limited information have been highlighted for future research, extending our understanding on the importance of ethylene during growth and senescence and boosting future research with the aim to improve the qualitative and quantitative traits of crops.
Ascorbate (AsA)-glutathione (GSH) cycle metabolism has been regarded as the most important defense mechanism for the resistance of plants under stress. In this study the influence of salicylic acid ...(SA) was studied on ascorbate-glutathione pathway, S-assimilation, photosynthesis and growth of mustard (Brassica juncea L.) plants subjected to 100 mM NaCl. Treatment of SA (0.5 mM) alleviated the negative effects of salt stress and improved photosynthesis and growth through increase in enzymes of ascorbate-glutathione pathway which suggest that SA may participate in the redox balance under salt stress. The increase in leaf sulfur content through higher activity of ATP sulfurylase (ATPS) and serine acetyl transferase (SAT) by SA application was associated with the increased accumulation of glutathione (GSH) and lower levels of oxidative stress. These effects of SA were substantiated by the findings that application of SA-analog, 2,6, dichloro-isonicotinic acid (INA) and 1 mM GSH treatment produced similar results on rubisco, photosynthesis and growth of plants establishing that SA application alleviates the salt-induced decrease in photosynthesis mainly through inducing the enzyme activity of ascorbate-glutathione pathway and increased GSH production. Thus, SA/GSH could be a promising tool for alleviation of salt stress in mustard plants.
Salicylic acid (SA) is known to affect photosynthesis under normal conditions and induces tolerance in plants to biotic and abiotic stresses through influencing physiological processes. In this ...study, physiological processes were compared in salt-tolerant (Pusa Vishal) and salt-sensitive (T44) cultivars of mungbean and examined how much these processes were induced by SA treatment to alleviate decrease in photosynthesis under salt stress. Cultivar T44 accumulated higher leaf Na
+ and Cl
− content and exhibited greater oxidative stress than Pusa Vishal. Activity of antioxidant enzymes, ascorbate peroxidase (APX) and glutathione reductase (GR) was greater in Pusa Vishal than T44. Contrarily, activity of superoxide dismutase (SOD) was greater in T44. The greater accumulation of leaf nitrogen and sulfur through higher activity of their assimilating enzymes, nitrate reductase (NR) and ATP-sulfurylase (ATPS) increased reduced glutathione (GSH) content more conspicuously in Pusa Vishal than T44. Application of 0.5
mM SA increased nitrogen and sulfur assimilation, GSH content and activity of APX and GR. This resulted in the increase in photosynthesis under non-saline condition and alleviated the decrease in photosynthesis under salt stress. It also helped in restricting Na
+ and Cl
− content in leaf, and maintaining higher efficiency of PSII, photosynthetic N-use efficiency (NUE) and water relations in Pusa Vishal. However, application of 1.0
mM SA resulted in inhibitory effects. The effect of SA was more pronounced in Pusa Vishal than T44. These results indicate that SA application alleviates the salt-induced decrease in photosynthesis mainly through inducing the activity of NR and ATPS, and increasing antioxidant metabolism to a greater extent in Pusa Vishal than T44.
•Salinity tolerance strategies are required for sustainable plant development.•Proline may act as target tool for salinity tolerance.•Phytohormones provide signals for proline accumulation and ...salinity tolerance.
Salinity is one of the most challenging problems that adversely affects growth and development of plants. Plants adopt various strategies to overcome the adverse effects of salinity stress. In recent years, phytohormones and osmolytes have been involved in reducing the adverse effect of salinity stress. Under salinity stress, osmolyte such as proline maintains cellular homeostasis through osmotic regulation and induces physiological processes favorably. The role of phytohormones under salinity stress is critical in modulating physiological responses that eventually lead to adaptation of plants to an unfavorable environment. The individual role of both proline and phytohormones has been extensively studied, but a comprehensive study on the interaction of phytohormones with proline under salinity stress is lacking. The present review focuses on enhancing our understanding on the mechanism of salinity tolerance via proline and phytohormones with emphasis on phytohormones interaction with proline under salinity stress.
We investigated the potential of salicylic acid (SA) in alleviating the adverse effects of heat stress on photosynthesis in wheat (Triticum aestivum L.) cv WH 711. Activity of ribulose ...1,5-bisphosphate carboxylase (Rubisco), photosynthetic-nitrogen use efficiency (NUE), and net photosynthesis decreased in plants subjected to heat stress (40°C for 6 h), but proline metabolism increased. SA treatment (0.5 mM) alleviated heat stress by increasing proline production through the increase in γ-glutamyl kinase (GK) and decrease in proline oxidase (PROX) activity, resulting in promotion of osmotic potential and water potential necessary for maintaining photosynthetic activity. Together with this, SA treatment restricted the ethylene formation in heat-stressed plants to optimal range by inhibiting activity of 1-aminocyclopropane carboxylic acid (ACC) synthase (ACS). This resulted in improved proline metabolism, N assimilation and photosynthesis. The results suggest that SA interacts with proline metabolism and ethylene formation to alleviate the adverse effects of heat stress on photosynthesis in wheat.
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