Variation in photosynthesis and growth of mustard cultivars: Role of ethylene sensitivity

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.