Changes in photosynthetic pigments, osmolytes and antioxidants of Indian mustard by drought and exogenous polyamines.

A pot experiment was performed as factorial based on randomized complete block design with three replications, to assess the effects of 1 mM spermidine (SPD) and 1 mM putrescine (PUT) on Indian mustard (Brassica Juncea L.) under different levels of watering (100, 75, 50 and 25% of field capacity). Chlorophyll a and b contents decreased, but the ratio of Chl a/b and carotenoid content increased with decreasing water supply. Foliar sprays of polyamines improved chlorophylls a and b and carotenoid contents, while the ratio of Chl a/b was reduced by these growth regulators. Relative water content, glycine betaine, proteins and soluble sugars contents were increased, but proline content was decreased by exogenous polyamines under limited water supply. Antioxidant enzyme (POX, CAT, SOD and APX) activities were enhanced by drought stress and polyamine treatments. This resulted in lower electrolyte leakage and lipid peroxidation (less MDA) under stressful conditions. The present results indicate that exogenous polyamines such as putrescine and spermidine can alleviate some of the deleterious impacts of water limitation on Indian mustard.