| 内聚力-张力学说的新证据(英文) |
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| 引用本文： | 李吉跃.内聚力-张力学说的新证据(英文)[J].中国林学,1999(2). |
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| 作者姓名： | 李吉跃 |
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| 作者单位： | 北京林业大学森林资源与环境学院!北京100083 |
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| 摘 要： | 虽然内聚力 -张力学说已经建立了一个多世纪 ,但要完全接受它仍有一些问题 ,因为它的一个推论是很难证实的 ,即木质部导管中存在大的负压 .特别是近年来木质部压力探针和Z型管试验的结果表明 ,引起空穴的木质部压力仅在 - 0 5MPa以上 .有人根据这一结果认为必须对木质部水分运输的内聚力 -张力学说加以修正 .但是 ,目前又有两个研究小组应用相似改良的Z型管方法测定了产生空穴的木质部压力 .他们的结果显示 ,不同树种木质部导管保持水分传导的压力范围在 - 1 2MPa到- 3 5MPa以下 .这表明树木木质部导管中存在较大负压 ,从而有力支持了内聚力 -张力学说
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| 关 键 词： | 内聚力-张力学说 负压 空穴 |
A New Evidence for the Cohesion\|tension Theory |
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| Li Jiyue.A New Evidence for the Cohesion\|tension Theory[J].Forestry Studies in China,1999(2). |
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| Authors: | Li Jiyue |
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| Abstract: | Although the cohesion\|tension theory has been well established for more than a century,some probelms have stood in the way of its complete acceptance because its corollary is difficult to prove:that large negative pressures exist in xylem conduits.Especially recent xylem pressure\|probe and Z\|tube experiments suggest that cavitation limits xylem pressures to above -0 5MPa,which may necessitate modification of the cohesion\|tension theory of xylem transport.Now another two research groups used a similar modified Z\|tube method to determine negative pressure causing cavitation in intact xylem conduits.This shows that xylem conduits of trees remained water\|filled and conductive to species\|specific pressures ranging from -1 2 to below -3 5 MPa,supporting the cohesion\|tension theory as the primary mechanism for water transport in trees. |
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| Keywords: | cohesion\|tension theory negative pressure cavitation |
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