Effects of drought stress on Non-enzymatic antioxidants and photosynthetic pigments of cotton plant species (Gossypium spp.)

To evaluate physiological responses of cotton genotypes to drought stress, this study was carried out in the 2015 cropping season at Garmsar agricultural research station. The experimental design was carried out in a factorial based on RCBD with 3 replications. The main plots were four cotton genotypes (G) including termus 14 (G. barbedense, tetraploid), varamin (G. herbaseum, tetraploid), Sorkhe and Garmsar landraces (G. herbaseum, Diploid). Factorial subplots (S×D) assigned to drought stress levels (S1: control or irrigation at 85% Fc and S2: irrigation at 40% Fc) and three levels of sampling time (D: 7, 14, and 21 days after final irrigation). Drought stress leads to an increase in photosynthetic pigments including chlorophyll a, chlorophyll b, and carotenoids. Drought stress also caused to increase in proline and soluble sugar contents so that Garmsar and Sorkhe varieties were superior to tetraploid ones. proline and carotenoids increased with time from the last irrigation. Drought stress leads to membrane lipid peroxidation that is demonstrated by increased amounts of Malonedialdhyde. Tetraploid genotypes, Varamin and Termuz 14 were more sensitive to drought stress than diploid ones. results showed that Sorkhe and Garmsar landraces possess physiological potentials for mitigation of drought effects. Integration of this potential with higher yields of superior commercial varieties will increase yield at water limiting conditions.