Studying the mechanism of drought stress in potato leaves at tuber expansion period by exogenous uniconazole revealed new insights into potato stress physiology. Therefore, a completely random pot experiments with time gradients of 5, 10 and 15 d of drought treatment. were carried out with uniconazole (40 mg L− 1) with respect to photosynthesis, active oxygen metabolism, antioxidant enzyme activity and the ascorbate-glutathione (AsA-GSH) cycle on varieties kexin No 1 (drought-tolerant, KX 1) and Atlantic (drought-sensitive, Atlantic). The results showed that uniconazole can effectively alleviate the degradation of chlorophyll under drought stress, Compared with CK, drought significantly inhibited the Pn, Tr, Gs and Ci of the leaves of the two potato varieties. Exogenous uniconazole effectively alleviated the inhibition of drought on the photosynthetic parameters of potato leaves, compared with D treatment, uniconazole reduced malondialdehyde (MDA), the rate of superoxide radical (O2−) and hydrogen peroxide (H2O2) content in leaves of KX 1 and Atlantic, and increased the activity of antioxidant enzymes in antioxidant defense system to remove excessive accumulation of reactive oxygen species (ROS) and reduce membrane lipid peroxidation, effectively alleviated the loss of yield factors caused by drought stress, and the drought-tolerant variety KX 1 was less damaged by drought than the drought-sensitive variety Atlantic, in addition, under drought stress, the antioxidant enzyme activity and non-enzymatic antioxidant content of the two varieties increased to adapt to the stress response caused by drought stress, D + S treatment could further increase the contents of osmotic adjustment substances (soluble protein and proline) and AsA-GSH cycle products and substrates, including ascorbic acid (AsA), dehydroascorbate (DHA), glutathione (GSH) and oxidized glutathione (GSSG), and increase the ratio of AsA/DHA and GSH/GSSG under drought stress in two potato varieties, so as to improve the level of reducing power and antioxidant capacity in leaves, thus reducing the damage of reactive oxygen species to cell membrane. The drought-tolerant variety KX 1 recovered better than the drought-sensitive variety Atlantic. These results provided a reference for the mechanism of drought resistance in potato and the effect of uniconazole on alleviating drought stress.
