Hydraulic properties of individual xylem vessels of Fraxinus americana.
Hydraulic properties of individual xylem vessels of Fraxinus americana.
复制标题
美洲白蜡单个木质部导管的水力特性。
DOI：
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发表时间：
2001
影响因子：
6.9
通讯作者：
N. M. Holbrook
中科院分区：
文献类型：
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作者：
M. Zwieniecki;P. Melcher;N. M. Holbrook
木质部导管的水力特性的研究一直局限于整个植物或整个茎段的测量。这种方法可以确定茎内血管集合的纵向运输特性，但提供的径向运输信息很少。本文对美国白蜡（Fraxinus americana L.）已经使用一种新的方法进行了检查，该方法允许检查单个容器的传输特性。本研究的一个目标是量化与栓塞修复相关的运输参数。两端开口（即无端壁）的血管段的纵向电导率与Poietille方程预测的值一致。径向比电导（每单位面积的电导）比血管段的纵向电导（由血管腔的横截面积归一化）低约6个数量级。当输送压力超过0.4MPa时，先前充气的血管的径向比电导出现阶跃增加。这与栓塞修复所需的正压可以在血管内分隔的想法一致，如果有边界的窝室充满气体。气体从充满空气的加压容器中运动的扩散系数与空气通过水扩散的扩散系数具有相同的数量级（1.95 e（-9）m（2）s（-1））。估计从充气容器中排出所有气体所需的时间约为20分钟，这表明气体去除可能不是栓塞修复的主要限制。
Studies of the hydraulic properties of xylem vessels have been limited to measurements of whole plant or whole stem segments. This approach allows the longitudinal transport properties of the ensemble of vessels within a stem to be determined, but provides little information on radial transport. Here the xylem of Fraxinus americana L. has been examined using a new method that allows the transport properties of individual vessels to be examined. One goal of this study was to quantify transport parameters relevant to embolism repair. The longitudinal conductivity of vessel segments open at both ends (i.e. no end walls) agreed with values predicted by the Poiseuille equation. Radial specific conductance (conductance per unit area) was approximately six orders of magnitude lower than the longitudinal conductance of the vessel segment normalized by the cross-sectional area of the vessel lumen. There was a step increase in the radial specific conductance of previously gas-filled vessels when the delivery pressure exceeded 0.4 MPa. This is consistent with the idea that positive pressure, required for embolism repair, can be compartmentalized within a vessel if the bordered pit chambers are gas-filled. The diffusion coefficient for the movement of gas from a pressurized air-filled vessel was of the same order of magnitude as that for air diffusing through water (1.95 e(-9) m(2) s(-1)). Estimates of the time needed to displace all of the gas from an air-filled vessel were in the order of 20 min, suggesting that gas removal may not be a major limitation in embolism repair.