Effects of Salinity and Potassium Application on Antioxidant Enzyme Activities and Physiological Parameters in Pearl Millet

A plot culture experiment was conducted in a greenhouse at University of Zabol, Iran, to study the effects of different salinity levels and potassium supply on pearl millet. The experiment was laid out in a completely randomized factorial design with three replicates. Potassium sulfate was used as the potassium source. The rates of potassium treatments were 0, 100, and 200 kg ha(-1). Pearl millet was subjected to different salinity levels (0, 4, 8, and 12 ds m(-1)) through addition of NaCl to irrigation water. Results showed that the increase in the salt concentration from control to 12 ds m(-1) decreased grain yield (38.7%) of millet plants. In this study, we found a negative relationship between potassium and proline accumulation at vegetative (r(2)=-0.75**) and reproductive stage (r(2)=-0.66**) in millet plants. Salt stress remarkably elevated the activities of CAT and GPX antioxidant enzymes at vegetative and reproductive stages. Furthermore, potassium application had significant effect on grain yield and increased it about 10.6% at the highest salinity treatment (12 ds m(-1)). Though, potassium treatment increased antioxidant activity in millet plants, it had no significant effect on proline content in leaves. Salinity treatment decreased potassium uptake but application potassium increased potassium content in leaves at two stages.