Cramer Michael D, Hawkins Heidi-Jayne, Verboom G Anthony
Department of Botany, University of Cape Town, Rondebosch, South Africa.
Oecologia. 2009 Aug;161(1):15-24. doi: 10.1007/s00442-009-1364-3. Epub 2009 May 16.
Transpiration is generally considered a wasteful but unavoidable consequence of photosynthesis, occurring because water is lost when stomata open for CO(2) uptake. Additionally, transpiration has been ascribed the functions of cooling leaves, driving root to shoot xylem transport and mass flow of nutrients through the soil to the rhizosphere. As a consequence of the link between nutrient mass flow and transpiration, nutrient availability, particularly that of NO(3)(-), partially regulates plant water flux. Nutrient regulation of transpiration may function through the concerted regulation of: (1) root hydraulic conductance through control of aquaporins by NO(3)(-), (2) shoot stomatal conductance (g(s)) through NO production, and (3) pH and phytohormone regulation of g(s). These mechanisms result in biphasic responses of water flux to NO(3)(-) availability. The consequent trade-off between water and nutrient flux has important implications for understanding plant distributions, for production of water use-efficient crops and for understanding the consequences of global-change-linked CO(2) suppression of transpiration for plant nutrient acquisition.
蒸腾作用通常被认为是光合作用的一种虽浪费但不可避免的结果，其发生是因为气孔打开以吸收二氧化碳时会失水。此外，蒸腾作用还具有冷却叶片、驱动根部到地上部木质部运输以及使养分通过土壤向根际进行质量流等功能。由于养分质量流与蒸腾作用之间的联系，养分有效性，尤其是硝酸盐（NO₃⁻）的有效性，会部分调节植物的水分通量。蒸腾作用的养分调节可能通过以下协同调节发挥作用：（1）通过硝酸盐（NO₃⁻）对水通道蛋白的控制来调节根部水力传导率；（2）通过一氧化氮的产生来调节地上部气孔导度（gs）；（3）pH值和植物激素对gs的调节。这些机制导致水分通量对硝酸盐（NO₃⁻）有效性呈现双相响应。水分通量与养分通量之间的这种权衡对于理解植物分布、培育水分利用效率高的作物以及理解全球变化相关的二氧化碳抑制蒸腾作用对植物养分获取的影响具有重要意义。
