Excess sulfur supplementation improves photosynthesis and growth in mustard under salt stress through increased production of glutathione

• Role of sulfur was assessed in photosynthesis of plants with/without salt.
• Sufficient-S and excess-S were equally effective in plants with no salt.
• Excess-S improved photosynthesis of salt grown mustard.
• The effects of excess-S was through increased GSH production.

Sulfur (S) assimilation leads to synthesis of reduced glutathione (GSH), a thiol compound known for its involvement in abiotic stress tolerance. In this study, the influence of sufficient-S (100 mg S kg−1 soil) and excess-S (200 mg S kg−1 soil) was studied on photosynthesis and growth of mustard (Brassica juncea L.) plants grown with or without 100 mM NaCl. Both the S levels equally promoted photosynthesis and growth of plants under no salt stress, while excess-S more conspicuously alleviated the negative effects of salt stress and improved photosynthesis and growth compared to the control plants. Excess-S mediated increase in photosynthesis and growth of salt grown plants was through increased production of GSH. The exogenous 1 mM GSH treatment and excess-S produced similar results on photosynthesis and growth of plants establishing that excess-S improves photosynthesis and growth under salt stress through increased GSH production. Thus, excess-S/GSH may be used as potential tool for alleviation of salt stress in mustard plants.