Scaling of angiosperm xylem structure with safety and efficiency
Scaling of angiosperm xylem structure with safety and efficiency
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DOI：
10.1093/treephys/26.6.689
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发表时间：
2006-06-01
期刊：
影响因子：
4
通讯作者：
Castro, L
中科院分区：
文献类型：
--
作者：
Hacke, UG;Sperry, JS;Castro, L
我们测试的假设，即更大的抗气蚀性与每艘船（坑面积假设）的总面积较小的船间坑面积相关，并评估了空化安全性和运输效率之间的权衡。14种不同的生长形式（藤本植物，环和散孔乔木，灌木）和家庭的亲和力被添加到已发表的数据主要是从蔷薇科（共29种）。结果表明，环孔树木和藤本植物的渗透系数随负压的增加而急剧下降，而散孔树木的渗透系数则随负压的增加而逐渐下降。环形多孔型曲线不是离心法的伪影，因为它也是用空气注射技术获得的。在物种之间比较曲线时，安全与效率的权衡是显而易见的：对于给定的压力，最佳脆弱性曲线的范围有限。在增加的抗空化性和减少的每个血管的孔膜面积（A（p））之间的强关系（r（2）= 0.77）支持孔面积假设。小Ap与小血管表面积相关，因此血管直径（D）较窄，血管长度（L）较短-与血管流阻增加和抗空化性一致。这种权衡放大在组织水平上的木质部/导管面积比的增加与空化阻力。环多孔物种比扩散多孔物种在导管的基础上，但不是在木质部的基础上，由于较高的木质部/导管面积比在环多孔解剖更有效。在四个数量级上，管腔和端壁电阻率保持相对紧密的比例，端壁中总血管电阻率的接近最佳平均值为56%。这与物种间L至D-3/2的基本比例一致。坑流阻力没有增加与空化安全，这表明空化压力是不相关的平均坑膜孔隙率。
We tested the hypothesis that greater cavitation resistance correlates with less total inter-vessel pit area per vessel (the pit area hypothesis) and evaluated a trade-off between cavitation safety and transport efficiency. Fourteen species of diverse growth form (vine, ring- and diffuse-porous tree, shrub) and family affinity were added to published data predominately from the Rosaceae (29 species total). Two types of vulnerability-to-cavitation curves were found. Ring-porous trees and vines showed an abrupt drop in hydraulic conductivity with increasing negative pressure, whereas hydraulic conductivity in diffuse-porous species generally decreased gradually. The ring-porous type curve was not an artifact of the centrifuge method because it was obtained also with the air-injection technique. A safety versus efficiency trade-off was evident when curves were compared across species: for a given pressure, there was a limited range of optimal vulnerability curves. The pit area hypothesis was supported by a strong relationship (r(2) = 0.77) between increasing cavitation resistance and diminishing pit membrane area per vessel (A(p)). Small Ap was associated with small vessel surface area and hence narrow vessel diameter (D) and short vessel length (L)-consistent with an increase in vessel flow resistance with cavitation resistance. This trade-off was amplified at the tissue level by an increase in xylem/vessel area ratio with cavitation resistance. Ring-porous species were more efficient than diffuse-porous species on a vessel basis but not on a xylem basis owing to higher xylem/vessel area ratios in ring-porous anatomy. Across four orders of magnitude, lumen and end-wall resistivities maintained a relatively tight proportionality with a near-optimal mean of 56% of the total vessel resistivity residing in the end-wall. This was consistent with an underlying scaling of L to D-3/2 across species. Pit flow resistance did not increase with cavitation safety, suggesting that cavitation pressure was not related to mean pit membrane porosity.