Comparative Effects of Salt and Alkali Stress on Antioxidant System in Cotton (Gossypium Hirsutum L.) Leaves

This pot experiment was to evaluate how salts (NaCl, Na2SO4) and alkali (Na2CO3+NaHCO3) affect the physiological and biochemical characteristics during the seedling stage of two cotton cultivars (salt-tolerant, L24; salt-sensitive, X45). Salt and alkali stress reduced seedling emergence rate, relative biomass, and chlorophyll content, however, the REC and MDA content increased. Salt and alkali stress increased markedly superoxide dismutase (SOD) activity. Peroxidase (POD) activity increased first and then decreased as the increase of salt and alkali stress. Catalase (CAT) activity initially increased and then decreased as NaCl stress increased. In addition, the SOD activity, REC, and MDA content was markedly higher in salt stress than that in alkali stress. The proline content of L24 was higher than that of X45 under salt and alkali stress. However, glycine betaine and soluble sugar content of 124 was lower than that of X45 under alkali stress. The REC and MDA content of 124 were lower than those of X45, however, the relative biomass, chlorophyll content, SOD, POD, CAT, and Pro were higher than those of X45. In conclusion, salt tolerant cotton cultivars may possess a superior protection effect by increasing antioxidant enzymes activity under salt and alkali stress.