Drought stress tolerance mediated by zinc-induced antioxidative defense and osmotic adjustment in cotton (Gossypium Hirsutum)

Zinc, as one of the essential microelements in crop plant, plays a crucial role in resistance to drought stress. To acquire a comprehensive of the physiological mechanism of resistance to drought stress enhanced by supplemental Zn in cotton, a hydroponic trial was conducted to investigate the changes in antioxidants and osmoregulation substances under zinc deficient and zinc sufficient conditions after 0, 3, 6 and 48 h of polyethylene glycol 6000-simulated drought stress. The present research showed that supplemental Zn significantly enhanced photosynthetic rate, chlorophyll a, chlorophyll b and dry matter of cotton under polyethylene glycol 6000 simulated drought stress, indicating that supplemental zinc improved the cotton growth. The antioxidant enzymes activities such as catalase, ascorbate peroxidase and superoxide dismutase, and non-enzymatic antioxidants such as carotenoid, reduced glutathione and ascorbic acid were all significantly enhanced and malonaldehyde content was remarkably reduced by supplemental zinc under polyethylene glycol 6000 simulated drought stress, indicating that the capacity of scavenging active oxygen species was improved by supplemental zinc in cotton. The osmoregulation substances such as soluble sugar, proline and soluble protein were all enhanced by supplemental zinc under Polyethylene glycol 6000 simulated drought stress, suggesting that zinc enhanced the osmotic adjustment capacity of cotton. It is implied that supplemental zinc could enhance the resistance to drought stress by inducing the buildup of antioxidative defences and osmotic adjustment ability in cotton.