Drought tolerance is defined by several morpho-physiological mechanisms that together improve plant development under water-limiting conditions. Previously, we found root hydraulic redistribution is one of those mechanisms for water stress avoidance. Herein, we aimed to verify the physiological mechanisms associated with root hydraulic redistribution and its consequences for leaf gas exchange and plant growth. Valencia sweet orange scions were grafted onto either Rangpur lime or Swingle citrumelo rootstock. Each plant had two root systems of the same rootstock in distinct pots, which allowed partial irrigation. Our results revealed that citrus species redistribute water under drought and this varies when comparing rootstocks, with Rangpur lime showing higher ability to redistribute water than Swingle citrumelo. For the first time, root hydraulic redistribution in Rangpur lime was associated with osmotic adjustment in well-watered roots of plants facing water deficit. Rangpur lime also presented an effective stomatal regulation of water loss and decreases in leaf transpiration likely allowed water transport to roots under water deficit. As conclusion, we found that root hydraulic redistribution, osmotic adjustment and stomatal control of leaf gas exchange are important physiological mechanisms associated with drought tolerance induced by Rangpur lime rootstock.

中文翻译：

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缺水条件下柑橘砧木根系渗透调节和叶片气体交换的气孔控制依赖于柑橘砧木

耐旱性由几种形态生理机制定义，这些机制共同改善了水分限制条件下的植物发育。以前，我们发现根系水力再分配是避免水分胁迫的机制之一。在此，我们旨在验证与根系水力再分配相关的生理机制及其对叶片气体交换和植物生长的影响。将瓦伦西亚甜橙接穗嫁接到 Rangpur 酸橙或 Swingle 柑橘砧木上。每株植物在不同的盆中都有两个相同砧木的根系，这允许部分灌溉。我们的结果表明，柑橘物种在干旱条件下会重新分配水分，并且在比较砧木时这种情况会有所不同，朗布尔石灰显示出比 Swingle citrumelo 更高的重新分配水分能力。首次，Rangpur 石灰中的根系水力再分配与面临缺水的植物的浇水良好的根部的渗透调节有关。Rangpur 石灰还表现出对水分流失的有效气孔调节，并且叶片蒸腾作用的减少可能允许水分在缺水情况下输送到根部。总之，我们发现根系水力再分配、渗透调节和叶片气体交换的气孔控制是与 Rangpur 石灰砧木诱导的耐旱性相关的重要生理机制。