Regulation of leaf and root physiology of sweet potato (Ipomoea batatas [L.] Lam.) with exogenous hormones under potassium deficiency stress

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ABSTRACTThe present study investigated the roles of exogenous hormones in mitigating the loss caused by potassium (K+) deficiency stress in terms of plant growth and physiology in sweet potato (Ipomoea batatas L. [Lam.]). Two cultivars, Xushu 32 (tolerant to K+ deficiency) and Ningzishu 1 (sensitive to K+ deficiency) were used for the study. Exogenous hormones (indole-3-acetic acid, IAA; gibberellin 3, GA3; abscisic acid, ABA) were applied foliarly on the 14th day of K+ deficiency stress (–K). After 5 days of application, the exogenous hormones significantly increased the chlorophyll content (Chl) and net photosynthetic rate (Pn), as well as the activities of antioxidant enzymes (superoxide dismutase, SOD; peroxidase, POD; catalase, CAT) in leaves, while reduced the lipid peroxidation levels (hydrogen peroxide, H2O2 and malondialdehyde, MDA). Application of hormones also significantly increased the root activity and alleviated the root tip cell damage. All these changes led to the enhancement of the plant dry weight, K+ content and K+ accumulation under – K condition, indicating that exogenous hormones can be used as potential tools to improve the K+ deficiency tolerance of sweet potato. However, exogenous IAA has a better effect on Xushu 32 than GA3 and ABA, while ABA is the best for Ningzishu 1.