Institute of Forest Botany, Mendel University of Agriculture and Forestry, Brno, Czech Republic.
New Phytol. 2009 Dec;184(4):932-43. doi: 10.1111/j.1469-8137.2009.03024.x. Epub 2009 Sep 14.
*Increasing evidence about hydraulic redistribution and its ecological consequences is emerging. Hydraulic redistribution results from an interplay between competing plant and soil water potential gradients. In this work, stem-mediated hydraulic redistribution was studied in a 53-year-old Douglas-fir tree during a period of drought. *Sap flux density measurements using the heat field deformation method were performed at four locations: in two large opposing roots and on two sides of the tree stem. Hydraulic redistribution was induced by localized irrigation on one of the measured roots, creating heterogeneous soil water conditions. *Stem-mediated hydraulic redistribution was detected during night-time conditions when water was redistributed from the wet side of the tree to the nonirrigated dry side. In addition to stem-mediated hydraulic redistribution, bidirectional flow in the dry root was observed, indicating radial sectoring in the xylem. *It was observed that, through stem-mediated hydraulic redistribution, Douglas-fir was unable to increase its transpiration despite the fact that sufficient water was available to one part of the root system. This resulted from the strong water potential gradient created by the dry soil in contact with the nonirrigated part of the root system. A mechanism of stem-mediated hydraulic redistribution is proposed and its possible implications are discussed.
越来越多的关于水力再分配及其生态后果的证据正在出现。水力再分配是植物和土壤水势梯度相互作用的结果。在这项工作中，在干旱期间研究了一棵 53 岁的道格拉斯冷杉中的茎介导水力再分配。使用热场变形法进行的 sap 通量密度测量在四个位置进行：在两个大的相对根系上和树干的两侧。通过在一个测量的根系上进行局部灌溉来诱导水力再分配，从而创造出不均匀的土壤水分条件。在夜间，当水从树木潮湿的一侧重新分配到未灌溉的干燥一侧时，检测到茎介导的水力再分配。除了茎介导的水力再分配外，还观察到干燥根系中的双向流动，表明木质部中的径向分区。尽管根系的一部分有足够的水，但观察到道格拉斯冷杉无法通过茎介导的水力再分配增加蒸腾作用，这是由于与根系未灌溉部分接触的干燥土壤产生的强烈水势梯度所致。提出了一种茎介导水力再分配的机制，并讨论了其可能的影响。
