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Different groundwater conditions affect leaf hydraulic conductance and leaf pressure-volume parameters in Populus euphratica at the extremely arid zone in the northwest of China.

Efficient water transport inside leaves constitutes a major determinant of plant function, especially in drought-stressed plants. The previous researches have reported the correlation between leaf hydraulic properties and water availability. In this study, we tested the hypothesis that water relation parameters of Populus euphratica in an extremely arid zone of China are sensitive and acclimated to groundwater depth. We measured leaf hydraulic conductance (K (leaf)) using rehydration kinetics methods (RKM), pressure-volume (P-V) curves, and leaf vulnerability curves of P. euphratica growing at four groundwater depth gradients. We also assessed the hydraulic safety margins across groundwater depth gradients. We found that K (leaf-max) shows an increasing trend as the groundwater depth increases, while osmotic potential at full turgor (pi(ft)) and turgor loss point (I-tlp) exhibits a decreasing trend, suggesting that increased tolerance to drought is formed as the groundwater depth increases. Furthermore, safety margins showed positive and negative variations under different groundwater depths, indicating that P. euphratica has formed special drought survival strategies, which can be summarized as a "conservative" strategy in favorable water conditions or a "risk" strategy in severe drought stress.