Foliar water uptake (FWU) is one of the primary water sources for desert plants. Desert plants’ water uptake capacity is essential in maintaining the balance of carbon and water. However, there are few studies on FWU capacity in desert plants and the physiological and ecological characteristics that lead to differences in FWU capacity. In order to clarify FWU strategies and the influencing factors of plants in desert ecosystems, this study measured the contact angle, FWU parameters, and hydraulic parameters to explore six desert plants’ FWU capacity and the effects of leaf wettability and hydraulic parameters on FWU capacity. The results showed that all six plants had FWU capacity, among which the leaves of Nitraria sibirica Pall. and Halimodendron halodendron (Pall.) Voss had a high foliar water uptake rate (k) and high foliar water uptake accumulation (FWU storage), and the leaves of Glycyrrhiza uralensis Fisch. had a high k and low FWU storage. The leaves of Populus euphratica Oliv., Apocynum hendersonii Hook. f., and Alhagi sparsifolia Shap. had a low k and low FWU storage. Additionally, FWU capacity was mainly affected by stomatal regulation compared with leaf wettability and leaf structure. The results of this study will help to improve the understanding of the physiological and ecological adaptability of desert plants.

Foliar water uptake (FWU) is considered to be a common phenomenon in most terrestrial plants. As a supplementary water source, it plays an important role in the growth and survival of plants in arid areas. However, there is no research to explain the water absorption of plant leaves from the perspective of gender specificity. To this end, we carried out a leaf water absorption capacity experiment and in situ wetting field experiment, respectively, in the early (Initial), middle (Mid) and end (End) of the growth season of male and female Populus euphratica. The results of the leaf water absorption capacity experiment showed that the FWU capacity of male and female P. euphratica showed an increasing trend with the growth period and reached the maximum at the End period. The FWU capacity of female P. euphratica was significantly greater than that of male P. euphratica after the Initial stage. The water absorption speed (k) of male and female leaves also increased with the growth period, but the increase was not significant. The increase in leaf water content per mg of water absorbed per unit of leaf area (LWC_A) of male P. euphratica was always greater than that of female P. euphratica. Specific leaf area (SLA), leaf water saturated deficit (WSD) and water absorption parameters (FWU capacity, k) were significantly correlated. The results of the in situ wetting field experiment show that humidification significantly increased the predawn water potential (Mid period) of female and male P. euphratica leaves and the net photosynthetic rate (Mid period) of male P. euphratica leaves, but had no significant effect on chlorophyll fluorescence parameters and anatomical structure. The MFA results show that the water status of male and female P. euphratica leaves was significantly correlated with photosynthetic parameters, fluorescence parameters and anatomical parameters. Our results show that the foliar water uptake capacity of female P. euphratica leaves was stronger than that of male P. euphratica and shows significant dynamic changes during the growing season. This was because female P. euphratica has a developed water storage structure. Foliar water uptake can effectively improve the water status and photosynthetic capacity of male and female P. euphratica, and this improvement was more significant during the most intense period of soil water stress. These findings will deepen our understanding of the ecological adaptation of dioecious plants to foliar water uptake.

The absorption of atmospheric water by plants through their leaves, known as leaf water uptake, plays a crucial role in sustaining plant growth and survival in arid regions. Condensate is one of the important sources of water for plants in arid zones and plays an important role in alleviating the physiological state of plant water. In order to clarify the ecological role of the leaf absorption of condensation water, we took the dominant species of the desert Dugay forest plant, Populus euphratica, as the research object, and based on in situ leaf humidification field experiments, we comprehensively analyzed the effect of condensation water on the physiological state of P. euphratica and the ecological benefit of leaf water absorption on the arid zone by determining the parameters of the physiological indexes of the leaf, the leaf wettability, and the water-absorbing capacity of the leaf. The results showed that P. euphratica leaves have a water-absorbing ability on both sides, and under the condensation water treatment, the water potential of dawn leaves in the TR group (−1.75 ± 0.12 MPa) was significantly higher than that in the CK group (−1.41 ± 0.13 Mpa); the net photosynthetic rate of leaves in the TR group (13.08 ± 0.68 μmol·m⁻²·s⁻¹) was significantly higher than that in the CK group (10.42 ± 0.57 μmol·m⁻²·s⁻¹); the proline content of the TR group (22.82 ± 0.8 μg·g⁻¹) was significantly lower than that of the CK group (68.67 ± 6.14 μg·g⁻¹); and the leaf photosynthetic capacity, leaf osmotic adjustment, and stress tolerance affected by condensation water were significantly different (p < 0.05). A leaf’s water-absorbing ability is mainly affected by leaf wettability, the proline content, and other influencing factors. The mean FWU rate was positively correlated with the mean transpiration rate. Within the Ebinur Lake watershed, the water absorption rate of P. euphratica leaves accounts for 10.92% of the maximum transpiration rate (T_r); in 2022, the total summer leaf surface water uptake by P. euphratica was about 220.5 mol, a value that represents about 0.25% of the average annual evapotranspiration from Ebinur Lake. This study helps to improve the understanding of the impact of condensation water on the physiological ecology of the desert plant P. euphratica and provides a scientific basis for the ecological benefits of leaf water absorption in arid regions.