IONOMIC AND ANTIOXIDANT SYSTEM RESPONSES TO Na2SO4 STRESS OF TWO COTTON CULTIVARS DIFFERING IN SALT TOLERANCE

Understanding the impact of salt stress on cotton growth, the antioxidant system, and ionomic responses is of great importance for maintaining cotton productivity and sustainability in arid regions. In this study, we investigated the physiological and ionomic responses of different cotton cultivars (salt-sensitive X45 and salt-tolerant L24) to Na2SO4 stress under greenhouse conditions. We found a low concentration of Na2SO4 mainly inhibited cotton shoot growth, whereas high concentrations of Na2SO4 significantly inhibited cotton shoot and root growth. The growth inhibition rate of Na2SO4 stress was higher for X45 than for L24. Na2SO4 stress increased relative electrical conductivity (REC) and malondialdehyde (MDA) and proline (Pro) contents. The REC and MDA content in L24 leaves were significantly lower than those in X45 leaves. As the Na2SO4 stress increased, the SOD, POD, and CAT activities increased first and then decreased; Pro in L24 continued to increase, but in X45, it first increased and then decreased. The activities of SOD, POD, and CAT, and the PRO content in L24 leaves were significantly higher than those in X45. The contents of Ca, Cu, B, and Mo in roots and Ca in leaves in both cultivars decreased significantly; L24 stored Na in cotton leaves under salt stress and transported more mineral elements to leaves (P, Cu, Ca, Mg, Zn, and B). However, X45 tended to accumulate more mineral elements in roots (Ca, Fe, and Mo). Correlation analysis showed that cotton mainly absorbed mineral elements in roots to resist Na2SO4 stress. It was concluded that cotton cultivars showed different reaction to Na2SO4 stress, and salt-tolerant cotton has a stronger antioxidant enzyme system, which allows ion homeostasis through root absorption of more mineral elements.