Water transport in vesselless angiosperms: conducting efficiency and cavitation safety
Water transport in vesselless angiosperms: conducting efficiency and cavitation safety
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DOI：
10.1086/520724
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发表时间：
2007-10-01
影响因子：
2.3
通讯作者：
Pittermann, J.
中科院分区：
文献类型：
--
作者：
Hacke, U. G.;Sperry, J. S.;Pittermann, J.
对被子植物无导管木材的两种结构-功能假说进行了检验。首先，无导管被子植物木材应该比针叶树木材具有更高的流动阻力，因为被子植物管胞缺乏低阻力的环面-边缘凹坑。第二，无导管木材应该是非常安全的空蚀，如果小累积面积的纹孔之间的管胞赋予安全（纹孔面积假说）。数据来自19种无导管被子植物的分支木材：Amborella sputterpoda，Trochodendron aralioides，Tetracentron sinense，以及来自Tasmannia，Zygogynum，Bubbia，Pseudowintera和Drimys的16种Winteraceae。与第一个假设相反，无导管和针叶树种与狭窄的管胞（低于约。18 μ m）具有相似的区域特异性。原因是无导管被子植物的管胞间纹孔阻力（平均16 +/- 2 MPa s m（-1））几乎与针叶树的管胞间纹孔阻力（6 +/- 1 MPa s m（-1））一样低，而远低于真双子叶植物的管胞间纹孔阻力（336 +/- 81 MPa s m（-1））。低抗点蚀性与从扫描电子显微镜观察和硅胶渗透推断的较大点蚀膜孔隙率相关，可能代表初期点蚀膜损失。孔阻力往往更大，在更广泛的被子植物管胞和掩盖任何下降木材电阻率与管胞宽度。为了支持第二个假设，无血管的木材平均空化压力为-3.4 +/- 0.3 MPa，这是低的潮湿的栖息地。在协议与坑面积假说，抗气蚀增加减少总坑面积之间的管道。然而，无导管被子植物更容易为一个给定的坑面积比真双子叶植物，符合其更具渗透性的坑膜。导管之间的小的总纹孔面积可能允许被子植物管胞具有更多的多孔膜以用于传导效率而不产生空化问题。
Two structure-function hypotheses were tested for vesselless angiosperm wood. First, vesselless angiosperm wood should have much higher flow resistance than conifer wood because angiosperm tracheids lack low-resistance torus-margo pits. Second, vesselless wood ought to be exceptionally safe from cavitation if the small cumulative area of pits between tracheids confers safety (the pit area hypothesis). Data were obtained from branch wood of 19 vesselless angiosperms: Amborella trichopoda, Trochodendron aralioides, Tetracentron sinense, and 16 Winteraceae from Tasmannia, Zygogynum, Bubbia, Pseudowintera, and Drimys. Contrary to the first hypothesis, vesselless and conifer species with narrow tracheids (below ca. 18 mu m) had similar area-specific resistivities. The reason was that vesselless angiosperms had an intertracheid pit resistance (mean 16 +/- 2 MPa s m(-1)) that was nearly as low as that of conifers (6 +/- 1 MPa s m(-1)) and much lower than that of eudicot intervessel pits ( 336 +/- 81 MPa s m(-1)). Low pit resistance was associated with greater pit membrane porosity inferred from scanning electron microscopy observations and silicone penetration and may represent incipient pit membrane loss. Pit resistance was often greater in wider angiosperm tracheids and obscured any drop in wood resistivity with tracheid width. In support of the second hypothesis, vesselless woods averaged a cavitation pressure of -3.4 +/- 0.3 MPa, which is low for their wet habitats. In agreement with the pit area hypothesis, resistance to cavitation increased with decreasing total pit area between conduits. However, vesselless angiosperms were more vulnerable for a given pit area than eudicots, consistent with their more permeable pit membranes. Small total pit area between conduits may allow angiosperm tracheids to have more porous membranes for conducting efficiency without creating a cavitation problem.