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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.

Plants are severely affected by salinity due to its high magnitude of adverse impacts and worldwide distribution. Among various strategies, nutrient management may be an important aspect in alleviating stress under varied environmental conditions. The uptake and assimilation of sulfur plays an inevitable and imperative role in determining plant growth and development and is a fundamental part of several important compounds, such as glutathione, co-enzymes, vitamins, phytohormones and reduced sulfur compounds that decipher growth and vigour of plants under optimal and stressful environments. Assimilatory sulfate reduction may induce salt tolerance by coordinating various physiological processes and molecular mechanisms which are likely to be induced b y phytohormones. Among phytohormones salicylic acid (SA) could provide tolerance against salinity stress by enhancing physiological processes and can improve salinity tolerance by its effect on sulfur assimilation pathway as biochemically or molecular mechanisms. The present review critically evaluates the recent studies on the modulation of sulfur assimilation and gives an insight into the role of glutathione to maintain redox state and their cumulative significance in plants’ tolerance to salinity by SA in inducing various physiological responses in plants under salinity stress.

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.

In this study, we have shown that application of ethephon (an ethylene source) resulted in increased activity of nitrate reductase (NR, EC 1.6.6.1) and ATP-sulfurylase (ATPS, EC 2.7.7.4), which accounted for enhanced nitrogen (N) and sulfur (S) assimilation, resulting in increased photosynthetic responses in two mustard ( Brassica juncea L.) cultivars that differ in photosynthetic capacity. These results were further substantiated by the effects of 100 μM norbornadiene (NBD; an ethylene action inhibitor) treatment. The application of NBD to ethephon-treated plants reduced ethylene sensitivity of plants and inhibited ethylene action by binding to the ethylene receptors, suppressing ethylene-induced N and S assimilation and photosynthetic responses in both the cultivars. Ethylene could be potentially used to increase available N and S resources, photosynthetic-NUE and -SUE and photosynthesis of mustard.

Ethylene is involved in various aspects of plant growth and development. We studied ethylene sensitivity in four mustard ( Brassica juncea L. Czern and Coss.) cultivars, Pusa Jai Kisan, Alankar, Basanti and SS2 using chemicals that modify ethylene production and examined its role in determining photosynthesis and growth. Pusa Jai Kisan showed maximum sensitivity to ethylene and was more responsive to ethylene modulators than SS2, which exhibited minimum sensitivity to ethylene. In the presence of ethephon (ethylene-source), Pusa Jai Kisan exhibited greatest increase in growth and the activity of ribulose-1,5-bisphosphate carboxylase (Rubisco), net photosynthesis, stomatal conductance and intercellular CO 2 concentration, and maximal decrease in these characteristics with ethylene action inhibitor, norbornadiene (NBD). Glucose treatment did not inhibit Rubisco activity, net photosynthesis and growth in ethylene-sensitive plants, but these characteristics were maximally inhibited in ethylene-insensitive plants. Our results show that ethylene sensitivity has a role in determining photosynthesis and growth of mustard plants. The selection of an ethylene-sensitive mustard type would help in augmenting photosynthesis and growth and also provide new insight into the ethylene-mediated physiological responses.

Cadmium (Cd) is a toxic heavy metal that enters the environment through various anthropogenic sources, and inhibits plant growth and development. Cadmium toxicity may result from disturbance in plant metabolism as a consequence of disturbance in the uptake and translocation of mineral nutrients. Plant nutrients and Cd compete for the same transporters and, therefore, presence of Cd results in mineral nutrients deficiency. The optimization of mineral nutrients under Cd stress could reduce Cd toxicity by greater availability at the transport site resulting in reduced accumulation of Cd, and could also alleviate Cd-induced toxic effects by enhancing biochemical reactions and physiological processes in plants. In the present review the role of plant macro, micro and beneficial elements in alleviating Cd stress in crop plants is discussed.

Salinity is a major abiotic stress factor affecting plant growth and productivity worldwide. The salinity-induced reduction in photosynthesis, growth and development of plants is associated with ionic/osmotic effects, nutritional imbalance or oxidative stress. Plants develop several mechanisms to induce tolerance to overcome salinity effects. Of the several possible mechanisms to reduce the effects of salinity stress, management of mineral nutrients status of plants can be the efficient defense system. Sulfur (S) is an important plant nutrient involved in plant growth and development. It is considered fourth in importance after nitrogen, phosphorus, and potassium. It is an integral part of several important compounds, such as vitamins, co-enzymes, phytohormones and reduced sulfur compounds that decipher growth and vigor of plants under optimal and stress conditions. The present review focuses on improving our understanding on the salinity effects on physiology and metabolism of plants and the importance of sulfur in salinity tolerance.

Mustard (Brassica juncea L.) cultivars Alankar (salt-tolerant) and PBM16 (salt-sensitive) plants were grown with 50 mM NaCl and were sprayed with 0.1, 0.5, and 1.0 mM salicylic acid (SA) to study the physiological processes determining salt tolerance and to observe the influence of SA application on the alleviation of NaCl-induced adverse effects. The content of leaf Na+, Cl−, H2O2, TBARS, and electrolyte leakage and the activity of SOD were higher in PBM16 than Alankar. In contrast, nutrients content, activity of APX and GR, glutathione content, photosynthetic and growth characteristics were higher in Alankar. Treatment of 50 mM NaCl resulted in increase of Na+ and Cl−, oxidative stress, activity of antioxidant enzymes and glutathione content, while nutrients content, photosynthetic, and growth characteristics decreased in both the cultivars. Application of 0.5 mM SA alleviated the negative effects of 50 mM NaCl maximally, but 1.0 mM SA proved inhibitory. The effect of SA was more conspicuous in Alankar than PBM16. It is concluded that the higher tolerance of Alankar was due to its lower leaf Na+ and Cl− content, higher nutrients content, and efficient antioxidant metabolism. The application of 0.5 mM SA substantially alleviated salt-induced adverse effects in Alankar.

Two mustard (Brassica juncea L. Czern and Coss.) cultivars, Pusa Jai Kisan and SS2 differing in cadmium (Cd) tolerance were treated with 0, 25 and 50 μmol L^(-1) Cd to study the physiological basis of difference in Cd tolerance. Cultivar SS2 (Cd sensitive) accumulated greater Cd in leaves than Pusa Jai Kisan (Cd tolerant). Further, SS2 also exhibited higher contents of thiobarbituric acid reactive substances (TBARS) and H2O2 and electrolyte leakage. However, the activities of antioxidant enzymes, catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were higher in Pusa Jai Kisan than those in SS2. Contrarily, the activity of superoxide dismutase (SOD) was higher in SS2 than that in Pusa Jai Kisan and was the greatest at 25 μmol L^(-1) Cd. Treatment of 25 μmol L^(-1) Cd induced the maximum activity of enzymes. However, the activity of GR increased up to 50 μmol L^(-1) Cd in both the cultivars. The non-enzymatic antioxidants ascorbate (AsA) and glutathione (GSH) were higher in Pusa Jai Kisan than that in SS2, whereas dehydroascorbate (DHA) and oxidized glutathione (GSSG) were higher in SS2. Photosynthesis and growth were adversely and maximally decreased by 50 μmol L^(-1) Cd treatment in both the cultivars, but SS2 exhibited greater reductions. The protection of photosynthesis and growth and lesser reduction in Pusa Jai Kisan were associated with its capacity to restrict accumulation of Cd in leaves resulting in lower level of TBARS and H2O2 and electrolyte leakage. Moreover, Pusa Jai Kisan exhibited efficient antioxidant metabolism for removal of Cd-induced reactive oxygen species.

Salinity is one of the major environmental factors limiting crop productivity. The effect of increasing salinity levels (0, 50, 100 mM NaCl) on growth, photosynthetic traits, leaf water potential, oxidative stress, enzymatic and non-enzymatic antioxidants was studied in Pusa Jai Kisan and SS2 cultivars of mustard (Brassica juncea L. Czern & Coss.) differing in ATP-sulfurylase activity at 30 days after sowing (DAS). The cultivar SS2 (low ATP-sulfurylase activity) accumulated higher content of Na+ and Cl− in leaf than root. SS2 also showed greater content of thiobarbituric acid reactive substances (TBARS) and H2O2 and higher decrease in growth, photosynthetic traits and leaf water potential than Pusa Jai Kisan with increasing salinity levels. Contrarily, Pusa Jai Kisan (high ATP-sulfurylase activity) exhibited higher Na+ and Cl− content in root than leaf, lower TBARS and H2O2 content and higher activity of catalase, ascorbate peroxidase and glutathione reductase. However, the activity of superoxide dismutase was greater in SS2 than Pusa Jai Kisan. Higher activity of ATP-sulfurylase in Pusa Jai Kisan resulted in increased content of glutathione, a reduced form of inorganic sulfur and an essential component of cellular antioxidant defense system. The lesser decrease in growth and photosynthesis in Pusa Jai Kisan was the result of lesser Na+ and Cl− in leaf, higher turgidity and increased activity of antioxidant enzymes and glutathione content.

Cadmium is known to reduce photosynthesis and overall growth of plants. Plants adopt several mechanisms of Cd detoxification, such as accumulation of sulfur-rich compounds, like glutathione (GSH) and its precursor cysteine. The accumulation of GSH is regulated by the activity of ATP-sulfurylase, a rate-limiting enzyme in sulfur assimilation. The carbon of Cys is provided through photosynthesis. Thus, a plant with the higher photosynthetic potential and ATP-sulfurylase activity may have the higher contents of Cys and GSH and therefore may provide for a greater tolerance to Cd stress. Mustard (Brassica juncea L. Czern and Coss.) cvs. Varuna (high photosynthetic potential) and RH30 (low photosynthetic potential) were subjected to 0 and 200 mg Cd/kg soil, and the activity of ATP-sulfurylase, the contents of Cys and GSH, oxidative stress, and activities of antioxidant enzymes were studied. Under 200 mg Cd/kg soil, cv. Varuna showed an increased ATP-sulfurylase activity, the higher contents of Cys and GSH, and the net photosynthetic rate than cv. RH30. In contrast, the activity of superoxide dismutase, the contents of thiobarbituric acid-reactive substances, and H2O2, and electrolyte leakage were found to be greater in cv. RH30 showing an increased oxidative stress than cv. Varuna. However, the activities of ascorbate peroxidase and glutathione reductase were greater in cv. Varuna than cv. RH30. The results show that a greater ATP-sulfurylase activity, an enhanced production of Cys and GSH, and an efficient antioxidant enzyme system in the high photosynthetic mustard cv. Varuna helped to the reduce the oxidative stress maintaing high photosynthesis.

To examine the possible relationship between the activity of 1-aminocyclopropane carboxylic acid synthase (ACS; EC 4.4.1.14) and growth of mustard (Brassica juncea L.), ACS activity, ethylene and plant growth were studied in the presence of ACS activity modulators in no-defoliation and defoliated plants. Growth of plants was greatest when subjected to defoliation of 50% lower leaves in the plant axis compared to defoliation of 25% lower leaves or no-defoliation. The activity of ACS in no-defoliation and defoliated plants was correlative with growth of plants. ACS activity and ethylene evolution in no-defoliation plants treated with 10 μM indole-3-acetic acid (IAA) and defoliated plants treated with water were equal and resulted in maximum plant growth. On the contrary, the application of 10 μM IAA on defoliated plants resulted in the increase in ACS activity and ethylene evolution to an extent that inhibited the growth. The application of 100 μM IAA on no-defoliation and defoliated plants increased ACS activity and ethylene evolution maximally and proved inhibitory for the plant growth. The association of ACS activity, ethylene evolution and growth of plants was further substantiated with the use of 50 μM aminoethoxyvinyl glycine (AVG) applied alone or in combination with 10 or 100 μM IAA. The application of AVG resulted in the inhibition of ACS activity and the growth of no-defoliation or defoliated plants. The results indicate that there exists a correlation between ACS activity, ethylene and the growth of mustard plants.

Mustard (Brassica juncea L.) is characterized by oblong-shaped leaves on the lower layers of axis. These leaves are poorly illuminated, remain below light photosynthetic compensation point and abscise at maturity. Earlier research has shown that the removal of these shaded leaves improves photosynthetic potential of the rest of the leaves, the overall growth and yield of the crop. Now we show that 50% removal of these leaves at pre-flowering stage, i.e. 40 days after sowing (DAS) enhances nitrogen assimilation in the leaves more substantially than defoliation at post-flowering stage, i.e. 60 DAS. Further, the changes in N assimilation were concurrent with the ethylene evolution. It is suggested that strategies that lead to the abscission of lower leaves at early stage of growth may be adopted for efficient N utilization, and ethylene may be considered as an important physiological tool.

Leaf carbonic anhydrase (CA) activity, net photosynthetic rate (PN), stomatal conductance (gS) and plant dry mass (DM) exhibited a dose-dependent response to cadmium (Cd) in wheat (Triticum aestivum L.) grown under low and sufficient zinc (Zn) levels at 30 d after seedling emergence in sand culture. Cadmium at 10 µM concentration enhanced CA, PN and DM at low Zn level but these remain unaltered at sufficient Zn. Stomatal conductance decreased with increasing CdCl2 concentration at both the Zn levels. Cd higher than 10 µM inhibited the characteristics irrespective of Zn level. The activity of superoxide dismutase (SOD) was not saturated the with highest Cd concentration (50µM) at both the Zn levels. However, the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) increased up to 25 µM Cd and decreased at 50 µM Cd at both the Zn levels. It is suggested that CA activity was induced at low Cd (10 µM) under low Zn level increasing the photosynthesis. The synergies among the activit...

The increasing concentration of cadmium (Cd) in agricultural soil has resulted in crop productivity loss. The activation of the antioxidative enzyme system and its synergy with sulphur assimilation may be required as one of the mechanisms for the alleviation of the effects of Cd. In the present study the activities of antioxidative enzymes and sulphur assimilation were studied in Cd-treated wheat (Triticum aestivum) cultivars to assess their involvement in determining yield potential. The cultivar WH542 (low yielding type) accumulated Cd to a greater amount in both root and leaf, and also exhibited higher contents of H 2 O 2 and thiobarbituric acid reactive substance and the activity of superoxide dismutase (EC 1.15.1.1) than cultivar PBW343 (high yielding type). The activities of other antioxidative enzymes, catalase (EC 1.11.1.6), ascorbate peroxidase (EC 1.11.1.11), glutathione reductase (EC 1.6.4.2) and glutathione peroxidase (EC 1.11.1.9), activity of ATP-sulfurylase (EC 2.7.7.4), sulphur content, photosynthetic, growth and yield characteristics were higher in PBW343 than in WH542 in Cd treatment compared to the control. The results suggest that the efficient functioning of enzymes of the antioxidative system and sulphur assimilation helped in alleviating the effects of Cd in PBW343, protected photosynthetic ability and maintained high yielding potential of the cultivar.

Soil salinity is a major problem effecting plant growth and production at a considerable rate. Alleviation of the adverse effects of salinity stress is desirable for development of salinity tolerant crops. Salinity causes osmotic stress, ionic stress and oxidative stress in plants and disturbs cellular homeostasis. Plants’ ability to tolerate osmotic stress depends on multiple biochemical pathways that facilitate retention of water and maintains ion homeostasis. Osmolytes are compounds found to increase under salinity stress and help in osmoregulation and in protection of enzyme activity, detoxification of reactive oxygen species and protection of membrane integrity. Organic osmolytes are the most talked about and are nontoxic even at high concentration. Manipulating the concentration of these osmolytes is an important strategy to develop salinity tolerant crops. The present study focuses on the importance of osmolytes in salinity tolerance with emphasis on major organic osmolytes.

Sulfur (S) assimilation results in the synthesis of cysteine (Cys), a common metabolite for the formation of both reduced glutathione (GSH) and ethylene. Thus, ethylene may have regulatory interaction with GSH in the alleviation of salt stress. The involvement of ethylene in the alleviation of salt stress by S application was studied in mustard (Brassica juncea cv. Pusa Jai Kisan). First, the effects of 0, 0.5, 1.0 and 2.0 mM SO4 (2) (-) were studied on photosynthetic and growth parameters to ascertain the S requirement as sufficient-S and excess-S for the plant. In further experiments, the effects of sufficient-S (1 mM SO4 (2) (-) ) and excess-S (2 mM SO4 (2) (-) ) were studied on the alleviation of salt stress-induced by 100 mM NaCl, and ethylene involvement in the alleviation of salt stress by S. Under non-saline condition, excess-S increased ethylene with less content of Cys and GSH and adversely affected photosynthesis and growth. In contrast, excess-S maximally alleviated salt stress due to high demand for S and optimal ethylene formation, which maximally increased GSH and promoted photosynthesis and growth. The involvement of ethylene in S-mediated alleviation of salt stress was further substantiated by the reversal of the effects of excess-S on photosynthesis by aminoethoxyvinylglycine (AVG), ethylene biosynthesis inhibitor. The studies suggest that plants respond differentially to the S availability under non-saline and salt stress and excess-S was more potential in the alleviation of salt stress. Further, ethylene regulates plants' response and excess S-induced alleviation of salt stress and promotion of photosynthesis.

Phytohormones are organic compounds that in small amount promote, inhibit, or modify physiological processes in plants. Researchers have recognized salicylic acid (SA) and jasmonic acid (JA) as a potential hormone. Application of SA and JA could provide tolerance against biotic and abiotic stresses such as salinity, temperature stress, heavy metal stress, etc. The role of SA and JA in the protection against abiotic stress is played by its ability to induce expression of genes coding proteins. A low concentration of SA and JA appears to be effective in tolerance to stress by enhancing physiological processes and improving salt tolerance by its effect on biochemical and molecular mechanisms. The present review gives an insight into the role of SA and JA in inducing various physiological responses in plants under salinity stress, and an interaction between these two phytohormones is also discussed.

The toxicity of cadmium (Cd) is an emerging environmental problem that has attracted the attention of plant scientists all over the world. It deteriorates soil, plant and human health. Researchers have focused their attention in evolving strategies to reduce its toxicity at cellular, molecular and/or whole plant level. Sulfur is an important plant nutrient that takes part in plant metabolism and provides vigor to plants under stressful environments. This nutrient element could be used in agricultural system for reducing Cd toxicity and increasing sustainability. Sulfur uptake results in the formation of the first stable product cysteine through a cascade of enzymatic reactions. The formation of cysteine leads to the synthesis of glutathione, a nonenzymatic antioxidant known to be involved in Cd detoxification either through quenching reactive oxygen species or formation of phytochelatin that binds Cd and sequester it into vacuole. Manipulation of sulfur-assimilating enzymes, cysteine, glutathione and/or phytochelatin content could possibly lead to Cd detoxification. The present work gives insight into the role of sulfur in the alleviation of Cd stress.

In order to ascertain the stomatal and photosynthetic responses of mustard to ethylene under varying N availability, photosynthetic characteristics of mustard grown with optimal (80 mg N kg(-1) soil) or low (40 mg N kg(-1) soil) N were studied after the application of an ethylene-releasing compound, ethephon (2-chloroethyl phosphonic acid) at 40 days after sowing (DAS). The availability of N influenced ethylene evolution and affected stomatal conductance and photosynthesis. The effect of ethylene was smaller under deficient N where plants contained higher glucose (Glc) sensitivity, despite high ethylene evolution even in the absence of ethephon, potentially because the plants were less sensitive to ethylene per se. Ethephon application at each level of N increased ethylene and decreased Glc sensitivity, which increased photosynthesis via its effect on the photosynthetic machinery and effects on stomatal conductance. Plants grown with sufficient-N and treated with 200 μl l(-1) ethephon exhibited optimal ethylene, the greatest stomatal conductance and photosynthesis, and growth. These plants made maximum use of available N and exhibited the highest nitrogen-use efficiency (NUE).

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.

Ethephon (2-chloroethyl phosphonic acid), an ethylene-releasing compound, influences growth and photosynthesis of mustard (Brassica juncea L. Czern & Coss.). We show the effect of nitrogen availability on ethylene evolution and how this affects growth, photosynthesis and nitrogen accumulation. Ethylene evolution in the control with low N (100 mg N kg(-1) soil) was two-times higher than with high N (200 mg N kg(-1) soil). The application of 100-400 microl x l(-1) ethephon post-flowering, i.e. 60 days after sowing, on plants receiving low or high N further increased ethylene evolution. Leaf area, relative growth rate (RGR), photosynthesis, leaf nitrate reductase (NR) activity and leaf N reached a maximum with application of 200 microl x l(-1) ethephon and high N. The results suggest that the application of ethephon influences growth, photosynthesis and N accumulation, depending on the amount of nitrogen in the soil.

Sulfur (S) is an essential nutrient element required in a large quantity by mustard. S regulates photosynthesis and plant growth through improving nitrogen (N) acquisition. Mustard cultivars Alankar, Varuna, Pusa Jai Kisan, and SS2 differing in S accumulation capacity calculated as sulfate transport index (STI) were tested for ATP-sulfurylase activity, S and N accumulation, photosynthesis, and shoot dry mass (DM) at 30 and 60 d after sowing (DAS). The activity of ATP-sulfurylase, shoot N content, net photosynthetic rate (P N), leaf area, and shoot DM of the cultivars were in the order: Pusa Jai Kisan>Alankar>Varuna>SS2. ATP-sulfurylase activity was strongly and positively correlated with P N and shoot DM in all the cultivars. Hence ATP-sulfurylase activity may be used as a physiological trait for augmenting photosynthesis and shoot DM.

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.