Interaction of phytohormones with the antioxidant and pro-oxidant systems of cotton under salt stress

Despite extensive studies on the physiological effects of salinity in cotton, the combined regulatory roles of phytohormones in modulating the plant antioxidant and pro-oxidant systems under salt stress remain poorly understood. The biochemical responses of cotton plant varieties with different salt tolerances were studied through the exogenous application of phytohormones. The study used cotton plants of Gossypium hirsutum L. species developed by classical cotton breeding (Gulistan and C-4727), two gene knockout cultivars (Porlok-1 and Porlok-4) and two cultivars developed through DNA marker-assisted introgression into local varities (Ravnak-1 and Ravnak-2). Based on the results obtained, the exogenous application of abscisic acid (ABA) was found to alleviate the negative effects of salinity in all varieties. Under laboratory conditions, in saline models with 1 % and 4 % NaCl (sodium chloride), significant biochemical indicators including antioxidant enzyme activities, as well as concentrations of endogenous ABA and proline were observed to increase respectively in Porlok-1, Porlok-4 and Gulistan cotton cultivars. The biochemical resistance of gene knockout cotton varieties such as Porlock varieties to abioticstresses has been confirmed by molecular studies. When these varieties were compared with unmodified cotton varieties, the modified lines exhibited higher antioxidant enzyme activity and greater synthesis of free proline, reducing sugars and phytohormones, indicating enhanced stress adaptation.