Branch junctions and the flow of water through xylem in Douglas-fir and ponderosa pine stems.
Branch junctions and the flow of water through xylem in Douglas-fir and ponderosa pine stems.
复制标题
花旗松和黄松茎的分支连接处和水流穿过木质部。
DOI：
10.1093/jxb/erg169
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发表时间：
2003
影响因子：
6.9
通讯作者：
J. Brooks
中科院分区：
文献类型：
--
作者：
P. Schulte;J. Brooks
在大多数植物中，从根到叶的木质部中的水流必须经过从主茎上长出的分枝的连接处。这些路口已被研究作为流量限制和液压分割机制的组成部分，以保护工厂的主轴。分支连接处的水力性质也影响分支相互作用的程度，并可对流向其他分支的流量变化作出响应。研究了两种针叶树枝条的连接点，特别强调了下游枝条之间的耦合。通过迫使染色剂穿过连接处定性地观察到流动，并且所得图案显示进入分支的流动仅限于对向木质部的一部分，直到连接处下方相当大的距离。通过测量相邻分支中的流动停止之前和之后的分支中的流速以及通过测量连接部的组件的水力阻力来定量地研究连接部。在相邻分支中的血流停止后，流入剩余分支的血流增加，但远低于基于假设两个分支完全耦合的分支连接处的简单阻力模拟的预测。因此，连接点下游的分支似乎在其相互连接性方面受到限制，因此在其相互作用的能力方面受到限制。
Water flowing through the xylem from the roots to the leaves of most plants must pass through junctions where branches have developed from the main stem. These junctions have been studied as both flow constrictions and components of a hydraulic segmentation mechanism to protect the main axes of the plant. The hydraulic nature of the branch junction also affects the degree to which branches interact and can respond to changes in flow to other branches. The junctions from shoots of two conifer species were studied, with particular emphasis on the coupling between the downstream branches. Flow was observed qualitatively by forcing stain through the junctions and the resulting patterns showed that flow into a branch was confined to just part of the subtending xylem until a considerable distance below the junction. Junctions were studied quantitatively by measuring flow rates in a branch before and after flow was stopped in an adjacent branch and by measuring the hydraulic resistance of the components of the junction. Following flow stoppage in the adjacent branch, flow into the remaining branch increased, but considerably less than predicted based on a simple resistance analogue for the branch junction that assumes the two branches are fully coupled. The branches downstream from a junction, therefore, appear to be limited in their interconnectedness and hence in their ability to interact.