Drought compromises plant's ability to replace transpired water vapor with water absorbed from the soil, leading to extensive xylem dysfunction and causing plant desiccation and death. Short-term plant responses to drought rely on stomatal closure, and on the plant's ability to recover hydraulic functioning after drought relief. We hypothesize a key role for abscisic acid (ABA) not only in the control of stomatal aperture, but also in hydraulic recovery. Young plants of Populus nigra L. were used to investigate possible relationships among ABA, non-structural carbohydrates (NSC) and xylem hydraulic function under drought and after re-watering. In Populus nigra L. plants subjected to drought, water transport efficiency and hydraulic recovery after re-watering were monitored by measuring the percentage loss of hydraulic conductivity (PLC) and stem specific hydraulic conductivity (K_stem). In the same plants ABA and NSC were quantified in wood and bark. Drought severely reduced stomatal conductance (g_L) and markedly increased the PLC. Leaf and stem water potential, and stem hydraulic efficiency fully recovered within 24 h after re-watering, but g_L values remained low. After re-watering, we found significant correlations between changes in ABA content and hexoses concentration both in wood and bark. Our findings suggest a role for ABA in the regulation of stem carbohydrate metabolism and starch mobilization upon drought relief, possibly promoting the restoration of xylem transport capacity.

中文翻译：

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干旱期间和干旱后脱落酸含量的变化与杨树茎中的碳水化合物动员和水力恢复有关。

干旱损害了植物用从土壤吸收的水代替蒸发的水蒸气的能力，导致广泛的木质部功能障碍，并导致植物干燥和死亡。植物对干旱的短期反应取决于气孔关闭，以及植物在干旱缓解后恢复水力功能的能力。我们推测脱落酸（ABA）的关键作用不仅在气孔孔径的控制中，而且在水力恢复中。年轻的植物黑杨L.用于研究在干旱之后再浇水ABA，非结构性碳水化合物（NSC）和木质部液压功能之间可能的关系。在黑杨通过测量水力传导率（PLC）和茎的比水力传导率（K _stem）的损失来监测遭受干旱，再浇水后水力输送和水力恢复的L.植物。在相同的植物中，ABA和NSC在木材和树皮中定量。干旱严重降低了气孔导度（g _L），并显着增加了PLC。再浇水后24 h，叶片和茎水势和茎水力效率完全恢复，但g _L值仍然很低。重新浇水后，我们发现木材和树皮中ABA含量的变化与己糖浓度之间存在显着相关性。我们的研究结果表明ABA在干旱缓解时调节干碳水化合物代谢和淀粉动员中的作用，可能促进木质部转运能力的恢复。