Ethylene-stimulated photosynthesis results from increased nitrogen and sulfur assimilation in mustard types that differ in photosynthetic capacity

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.

► The role of ethylene in regulating photosynthesis at the whole plant level is not clear.
► Ethylene increases photosynthesis via its influence on N and S assimilation enzymes and subsequent incorporation of N and S into photosynthetic machinery.
► The influence of ethylene was on stomatal response and photosynthetic machinery.
► The differential photosynthetic capacity of genotypes was a result of variation in ethylene sensitivity.