A potential role for xylem-phloem interactions in the hydraulic architecture of trees: effects of phloem girdling on xylem hydraulic conductance.
A potential role for xylem-phloem interactions in the hydraulic architecture of trees: effects of phloem girdling on xylem hydraulic conductance.
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DOI：
10.1093/treephys/24.8.911
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发表时间：
2004-08
期刊：
影响因子：
4
通讯作者：
M. Zwieniecki;P. Melcher;T. Feild;N. Holbrook
中科院分区：
文献类型：
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作者：
M. Zwieniecki;P. Melcher;T. Feild;N. Holbrook
我们研究了红枫和糖枫沼泽中韧皮部与木质部的相互作用。我们的实验方法使我们能够通过测量在两个输送压力下供应到小侧枝切割端的水的流量来确定完整枝条的木质部电导率。我们发现，去除去离子水输送到树枝的点上游的树皮组织（韧皮部环剥）会导致树枝木质部水力传导率下降（红色A. 24%，A. saccharum 15%）。环剥水力传导率的下降伴随着木质部汁液渗透浓度的下降。韧皮部环剥后木质部汁液浓度的降低表明韧皮部的离子重新分布是造成观察到的水力传导率下降的原因。当对灌注KCl溶液（约140 mOsm kg(-1)）的树枝进行相同的测量时，韧皮部环剥对木质部水力传导没有影响。这些结果表明韧皮部和木质部水力系统之间存在功能联系，该联系是由细胞液离子含量的变化介导的。
We investigated phloem-xylem interactions in Acer rubrum L. and Acer saccharum Marsh. Our experimental method allowed us to determine xylem conductance of an intact branch by measuring the flow rate of water supplied at two delivery pressures to the cut end of a small side branch. We found that removal of bark tissue (phloem girdling) upstream of the point at which deionized water was delivered to the branch resulted in a decrease (24% for A. rubrum and 15% for A. saccharum) in branch xylem hydraulic conductance. Declines in hydraulic conductance with girdling were accompanied by a decrease in the osmotic concentration of xylem sap. The decrease in xylem sap concentration following phloem girdling suggests that ion redistribution from the phloem was responsible for the observed decline in hydraulic conductance. When the same measurements were made on branches perfused with KCl solution (approximately 140 mOsm kg(-1)), phloem girdling had no effect on xylem hydraulic conductance. These results suggest a functional link between phloem and xylem hydraulic systems that is mediated by changes in the ionic content of the cell sap.