Effect of Pix regulator on growth parameters of antioxidant enzymes and oxidative indices of seedlings of two cultivars of Sahel and Shayan cotton plant (Gossypium spp.) under different drought levels

Mepiquat chloride (PIX) is an important management tool to reduce stress damage in cotton plants during germination. In this study, the effects of different drought levels and the amount of mepiquat chloride (PIX) were investigated on growth indices and antioxidant enzymes as well as the malondialdehyde and hydrogen peroxide contents of seedlings in two cotton cultivars under laboratory conditions. The study was laid in a completely randomized design using 0, 5, and 10 g/l Pix and also under different drought levels using 0, -4, and -8 bar polyethylene glycol 6000 in petri dishes on two cultivars of cotton plant, namely Sahel (drought sensitive) and Shayan (drought resistant). Germination indices as well as physiological parameters of seedlings were measured under drought and Pix treatment after 4 days. Results showed that the use of Pix increased the germination percentage, root length, dry and fresh weights of seedlings, and the activity of peroxidase and catalase enzymes of cotton cultivars under drought stress while drought stress alone reduced these parameters. Drought also increased oxidative indices such as malondialdehyde and hydrogen peroxide in seedlings of Sahel and Shayan cultivars while Pix application reduced these indices. In general, the results of this study showed that the use of Pix improved growth responses and antioxidant system of the two cotton cultivars and the response of cultivar Shayan was better than Sahel.