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Drought stress is becoming a major threat to plant productivity loss in agricultural system. The present study was carried out to evaluate the physiological and biochemical alterations induced by salicylic acid (SA) in mustard plant under moderate drought stress conditions. Therefore, a pot culture experiment was conducted to test whether SA application at concentration of 0.5 mM through foliar spray could protect the mustard (Brassica juncea L.) cultivar Pusa Jai Kisan subjected to drought stress on the basis of growth and photosynthesis. The treatments were as follows: (i) 100% FC + 0 mM SA, (ii) 50% FC + 0 mM SA, (iii) 100% FC + 0.5 mM SA and (iv) 50% FC + 0.5 mM SA. The control treatment received 100% field capacity (FC) irrigation, whereas moderate drought stress corresponded to 50% field capacity. Plants subjected to drought stress caused significant reduction in growth and photosynthetic parameters, activity of ribulose 1,5-bisphosphate carboxylase (Rubisco), nitrate reductase (NR), ATP-sulfurylase (ATPS) which accounted for decreased nitrogen (N) and sulfur (S) assimilation. Whereas, a pronounced increase was observed in proline metabolism. Exogenously applied 0.5 mM SA alleviated the stress by increasing the proline production through the increase in γ-glutamyl kinase (GK) and decrease in proline oxidase (PROX) activity. In addition SA application restricted the ethylene formation by inhibiting the 1-aminocyclopropane carboxylic acid synthase (ACS) activity more conspicuously under moderate drought stress than no stress. These findings reflect that SA application alleviates the drought-induced decrease in growth and photosynthesis through increased proline content. Higher proline content was a result of increased N and S assimilation and increased synthesis of proline synthesizing enzyme which lowers the oxidative stress in mustard.

Heat stress is a major abiotic stress of global concern, affecting plant growth and production of plants, particularly crops worldwide. It occurs due to disturbance in plant metabolism as a consequence of excess generation of reactive oxygen species (ROS), which leads to oxidative stress. Plants adopt different strategies to overcome the adverse effects of heat stress. The molecular mechanism of the heat stress responses and breeding of heat-tolerant plants is essential to protect the food production. Recently, the role of salicylic acid has received attention in the regulation of numerous developmental processes under heat stress condition and has emerged through cross talk between chemical signaling pathways. The present review focuses on improving our understanding on the mechanism to induce thermotolerance in plants by salicylic acid interaction and gives an insight into some scientific approaches to modulate plants’ responses for high temperature tolerance.

Cadmium (Cd) stress is one of the most challenging environmental problems that adversely affects growth and development of plants. Plants adopt various strategies to overcome the adverse effects of Cd stress. Among these, recently phytohormones and osmolytes have been involved in overcoming the adverse effects of Cd stress. Proline is an important osmolyte that maintains cellular homeostasis through osmotic regulation and regulates physiological processes under Cd stress. The role of phytohormones under Cd stress is critical in modulating physiological responses that eventually leads 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 Cd is lacking. The present study focuses on enhancing our understanding on the mechanism of Cd tolerance via proline and phytohormones with emphasis on phytohormones’ interaction with proline under Cd stress.

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.