Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
Proc Natl Acad Sci U S A. 2010 Dec 28;107(52):22722-7. doi: 10.1073/pnas.1012194108. Epub 2010 Dec 13.
Plant vascular networks are central to botanical form, function, and diversity. Here, we develop a theory for plant network scaling that is based on optimal space filling by the vascular system along with trade-offs between hydraulic safety and efficiency. Including these evolutionary drivers leads to predictions for sap flow, the taper of the radii of xylem conduits from trunk to terminal twig, and how the frequency of xylem conduits varies with conduit radius. To test our predictions, we use comprehensive empirical measurements of maple, oak, and pine trees and complementary literature data that we obtained for a wide range of tree species. This robust intra- and interspecific assessment of our botanical network model indicates that the central tendency of observed scaling properties supports our predictions much better than the West, Brown, and Enquist (WBE) or pipe models. Consequently, our model is a more accurate description of vascular architecture than what is given by existing network models and should be used as a baseline to understand and to predict the scaling of individual plants to whole forests. In addition, our model is flexible enough to allow the quantification of species variation around rules for network design. These results suggest that the evolutionary drivers that we propose have been fundamental in determining how physiological processes scale within and across plant species.
植物的维管网络是植物形态、功能和多样性的核心。在这里，我们提出了一个植物网络缩放的理论，该理论基于维管系统沿着最佳空间填充以及水力安全和效率之间的权衡。纳入这些进化驱动力会导致对液流、木质部导管半径从树干到末梢小枝的锥度以及木质部导管频率如何随导管半径变化的预测。为了验证我们的预测，我们使用了枫树、橡树和松树的全面的经验测量数据以及我们为广泛的树种获得的补充文献数据。我们对植物网络模型进行了稳健的种内和种间评估，结果表明，观察到的缩放特性的中心趋势比 West、Brown 和 Enquist (WBE) 或管道模型更能支持我们的预测。因此，我们的模型比现有的网络模型更准确地描述了血管结构，应该作为理解和预测个体植物到整个森林的缩放的基准。此外，我们的模型足够灵活，可以量化网络设计规则周围的物种变异。这些结果表明，我们提出的进化驱动力对于确定生理过程在植物物种内和物种间的缩放方式具有重要意义。
