Abstract This study aimed at determining the role of aquaporins (AQPs) in the anisohydric behavior of sunflower. Deactivation of AQPs by mercury revealed that they could play vital role in the stomatal regulation and this role was not time-dependent under the control conditions. Sunflower seedlings were exposed to drought or to osmotic or ionic factor of NaCl and KCl. Under control and optimal conditions, sunflower leaves behaved in an anisohydric manner (maintaining high stomatal conductance (gs) at 13:00 compared to 9:00). At 13:00: 1) the upregulation of PIP1;1 could improve the mesophyll conductance to CO2, leading to enhancement of the photosynthetic rate (A) and consequently increasing the gs and 2) PIP2s were downregulated in the leaves, perhaps to decrease the hydraulic conductance and control excess water loss via transpiration but at the same time these genes were upregulated in the roots to improve root to leaf hydraulic conductance and maintain the positive water balance of the whole plant. Under drought, the decrease in gs and A at 13:00 could imply a shift towards near-isohydric behavior. The downregulation of PIP1s and further downregulation of PIP2s could indicate their involvement in this shift by decreasing CO2 permeability and avoiding the possible loss of water from the plant roots to soil, respectively. The anisohydric behavior of leaves treated with KCl, but not NaCl, (25 or 150 mM) could be due to the positive impact of K+ on stomata and the regulation of PIP1s and PIP2s. The anisohydric behavior could be achieved by a synchronized regulation of leaf and root AQPs.

中文翻译：

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根叶PIP1和PIP2的互补作用驱动了向日葵的无等水行为

摘要 本研究旨在确定水通道蛋白 (AQP) 在向日葵的脱水行为中的作用。汞对 AQP 的失活表明它们在气孔调节中起着至关重要的作用，并且在控制条件下，这种作用不是时间依赖性的。向日葵幼苗暴露于干旱或NaCl和KCl的渗透或离子因子。在控制和最佳条件下，向日葵叶子以非等水体方式表现（与 9:00 相比，在 13:00 保持高气孔导度 (gs)）。13:00: 1) PIP1;1 的上调可以提高叶肉对 CO2 的电导，导致光合速率提高 (A) 从而增加 gs 和 2) PIP2s 在叶片中被下调，也许是为了降低水力传导度并通过蒸腾作用控制过量水分流失，但同时这些基因在根部上调以改善根叶水力传导度并维持整个植物的正水分平衡。在干旱情况下，13:00 时 gs 和 A 的减少可能意味着向近等水行为的转变。PIP1s 的下调和 PIP2s 的进一步下调可能表明它们分别通过降低 CO2 渗透性和避免水分从植物根部流失到土壤中参与了这种转变。用 KCl 而不是 NaCl (25 或 150 mM) 处理的叶片的缺水行为可能是由于 K+ 对气孔的积极影响以及 PIP1s 和 PIP2s 的调节。叶和根 AQP 的同步调节可以实现不等水行为。