Department of Forest Ecology, University of Helsinki, PO Box 27, FI-00014 Helsinki, Finland.
Tree Physiol. 2010 Nov;30(11):1433-47. doi: 10.1093/treephys/tpq085.
We studied the effect of tree architecture on xylem anatomy in three Betula pendula Roth., three Picea abies (L.) H. Karst. and three Pinus sylvestris (L.) trees (mean age 35 years). First, the analysis of conduit anatomy in different tree parts showed that conduits tapered and their frequency increased from roots (≥ 2 mm) to stem, from stem to branches and further to leaf petioles in B. pendula. Conduit anatomy in lateral and main roots, as well as lateral and main branches, significantly differed from each other in all the studied species. The increase in conduit diameter and decrease in frequency from the pith to the bark were clear aboveground, but variable patterns were observed belowground. In the leaf petioles of B. pendula, conduit diameter increased and conduit frequency decreased with increasing individual leaf area. Second, the results concerning the scaling of conduit diameter were compared with the predictions of the general vascular scaling model (WBE model) and Murray's law. The scaling parameter values at the tree level corresponded with the predictions of the WBE model in all the studied trees except for one tree of both conifer species. However, the scaling parameter values changed from one tree compartment to another rather than remaining uniform inside a tree, as assumed by the WBE model. The assumptions of the WBE model of a constant conductivity ratio, constant tapering and an unchanged total number of conduits were not fulfilled. When the conductivity ratio and relative tapering were plotted together, the results aboveground corresponded quite well with Murray's law: the conductivity ratio increased when relative tapering decreased. Our results support the theory that trees adjust both their macro- and microstructure to maximize their water transport efficiency, but also to prevent embolism and ensure mechanical safety.
我们研究了 3 株欧洲白桦（Betula pendula Roth.）、3 株欧洲云杉（Picea abies (L.) H. Karst.）和 3 株欧洲赤松（Pinussylvestris (L.)）的树木结构对木质部解剖结构的影响（平均年龄 35 年）。首先，对不同树木部位导管解剖结构的分析表明，在欧洲白桦中，导管从根部（≥2 毫米）到茎干、从茎干到树枝、再到叶叶柄逐渐变细，其频率逐渐增加。在所有研究的树种中，侧根和主根以及侧枝和主枝的导管解剖结构都存在显著差异。导管直径从髓心到树皮逐渐增大，频率逐渐减小，这一现象在地上部分较为明显，但地下部分的变化模式则有所不同。在欧洲白桦的叶柄中，导管直径随个体叶面积的增加而增大，导管频率则随之减小。其次，导管直径的缩放结果与通用血管缩放模型（WBE 模型）和 Murray 定律的预测进行了比较。除了两种针叶树的一棵树外，所有研究树种的树木水平缩放参数值均与 WBE 模型的预测相符。然而，与 WBE 模型所假设的那样，缩放参数值在树木的不同部位之间发生了变化，而不是在树木内部保持一致。WBE 模型关于导管传导率比恒定、变细恒定和导管总数不变的假设并不成立。当将传导率比和相对变细率一起绘制时，地上部分的结果与 Murray 定律非常吻合：相对变细率降低时，传导率比增加。我们的研究结果支持这样一种理论，即树木会调整其宏观和微观结构，以最大限度地提高其水分运输效率，但也要防止栓塞并确保机械安全。
