Physiological Response of Cotton to Salinity at Various Growth and Development Stages

Response of cotton (Gossypium hirsutum) variety LH 1556 was studied in pot experiment at different levels of salinity. Salt stress was applied by adding NaCI to a salinity level of E.C. 0, 4, 8 and 12 ds m⁻¹ at five stages of growth viz. sowing, emergence of seedling, square formation, flowering and boll formation. Seedling stage was observed to be the most sensitive to salinity. Chlorophyll and protein content decreased while soluble sugars and catalase activity increased. Changes in metabolism led to synthesis of large amounts of protein which contributed towards membrane formation and soluble sugars to maintain the osmotic pressure. In high salt treatment, higher constitutive levels of catalase, indicate higher capacity for the decomposition of H₂O₂. The reduction in dry matter at higher salinity could be due to the toxic effect of added salts, physiological scarcity of water or altered carbon and nitrogen metabolism.