Water scarcity is one of the major factors restricting grape cultivation in arid and semi-arid regions of China. Kaolin particle film (KPF) has shown great potential in alleviating crop stress and improving water use efficiency. To further investigate how KPF alleviate drought stress at physiological level, this study evaluated the drought index, leaf relative water content (RWC), photosynthesis, antioxidant properties, and osmotic adjustment ability of Cabernet-Sauvignon seedlings leaves in controlled greenhouse under three conditions: natural drought (ND), natural drought + KPF (ND + KPF) and normal irrigation (NI). Measurements were taken on 0, 5, 9, 13 and 17 days post drought treatment. The results indicated that foliar application of KPF during natural drought progression reduced the seedling drought index by 10.98–38.30%, increased net photosynthesis (An) by 48.40–134.75%, thereby partially alleviated drought stress. Concurrently, KPF decreased stomatal conductance (gs), leading to a reduction in leaf transpiration (E) by 24.05%-59.83% and an increase in leaf relative water content (RWC) by 5.12–10.03%. Furthermore, KPF treatment significantly lowered the leaf contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA) by 8.73–31.22% and 19.89–21.79%, respectively, indicating mitigated oxidative stress. KPF-treated plants exhibited lower activity of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), as well as reduced accumulation of glutathione (GSH), ascorbic acid (ASA), proline and soluble protein during the early and middle stages of stress. Meanwhile, it helped sustain essential metabolic activity at the peak of stress severity. These findings suggest that KPF does not primarily function by chemically activating defense responses, but rather through a physical mechanism. Specifically, KPF likely acts as an antitranspirant, reducing the adverse effects of drought by maintaining favorable cellular water status. This study provides new insights into the mechanisms by which KPF mitigates drought stress in crops.
Wang et al. (Fri,) studied this question.