Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy.
Tree Physiol. 2010 May;30(5):628-35. doi: 10.1093/treephys/tpq017. Epub 2010 Mar 25.
This study reports experimental evidence for light-mediated changes of stem hydraulic conductance (K(stem)) in field-grown laurel plants. Field measurements based on the evaporative flux method revealed that sun-exposed branches had 60% higher K(stem) with respect to shade-exposed branches. Xylem sap potassium concentration was approximately 3 mM as recorded in shaded branches and up to 12 mM in illuminated ones. Such a difference in [K(+)] proved to induce significant increase in xylem hydraulic conductance of excised twigs when artificially perfused with various solutions, as a likely consequence of the interaction of cations with the pectic matrix of pit membranes (the so-called 'ionic effect'). We propose that this mechanism provides plants with a large potential for fine regulation of water flow towards different parts of the canopy exposed to different environmental conditions with the result of optimizing light and water utilization.
本研究报告了田间生长的月桂植物中，光介导的茎水力传导度（K(stem)）变化的实验证据。基于蒸发通量法的田间测量表明，与遮荫部位相比，暴露于阳光下的树枝的 K(stem) 增加了 60%。在遮荫部位记录到的木质部汁液钾浓度约为 3mM，而在光照部位则高达 12mM。这种 [K(+)] 的差异被证明在通过各种溶液人工灌注时会显著增加离体嫩枝的木质部水力传导度，这可能是阳离子与纹孔膜果胶基质相互作用的结果（所谓的“离子效应”）。我们提出，这种机制为植物提供了一种很大的潜力，可以精细调节流向树冠不同部位的水流，以适应不同的环境条件，从而优化光和水的利用。
