Physiological response of potato leaves to uniconazole under drought stress during the tuber expansion period

Long-term drought stress has irreversible effects on potato growth and reduces yield. Uniconazole can alleviate the growth inhibition and plant damage resulting from drought stress. In the current study, the effects of drought stress on the leaf physiology and yield of two potato varieties (Kexin No. 1, drought-tolerant, and Atlantic, drought-sensitive) and the ability of uniconazole to promote growth and productivity under drought conditions were studied. The results showed that uniconazole could effectively alleviate the degradation of chlorophyll under drought stress, and drought significantly inhibited the photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s), and intercellular CO₂ concentration (C_i) of the leaves of the two potato varieties. Exogenous uniconazole effectively alleviated the inhibitory effect of drought on the photosynthetic parameters of potato leaves. Compared with drought treatment, uniconazole treatment reduced malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and superoxide anion (O₂⁻) production in the leaves of Kexin No. 1 and Atlantic plants and increased the activity of antioxidant enzymes, alleviating the loss of yield factors caused by drought stress. In addition, the antioxidant enzyme activity and nonenzymatic antioxidant activity of both varieties increased in response to drought stress. Drought + uniconazole treatment further increased the contents of the osmotic adjustment substances soluble protein and proline and ascorbate-glutathione (ASA-GSH) cycle products and substrates, including ascorbic acid (ASA), dehydroascorbate (DHA), glutathione (GSH) and oxidized glutathione (GSSG). Drought + uniconazole treatment also increased the ratio of ASA/DHA and GSH/GSSG in the two potato varieties under drought stress. This enhancement elevated the levels of reducing power and antioxidant capacity in the leaves, thus reducing the impacts of reactive oxygen species on the cell membrane. The drought-tolerant variety Kexin No. 1 exhibited a greater recovery than did the drought-sensitive variety Atlantic. These results provide a valuable reference for understanding the mechanism of drought resistance in potato plants and the effectiveness of uniconazole in alleviating drought-induced stress.