Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131 USA.
Am J Bot. 2009 May;96(5):877-84. doi: 10.3732/ajb.0800380. Epub 2009 Apr 13.
Many characteristics of plants and animals scale with body size as described by allometric equations of the form Y = βM(α), where Y is an attribute of the organism, β is a coefficient that varies with attribute, M is a measure of organism size, and α is another constant, the scaling exponent. In current models, the frequently observed quarter-power scaling exponents are hypothesized to be due to fractal-like structures. However, not all plants or animals conform to the assumptions of these models. Therefore, they might be expected to have different scaling relations. We studied one such plant, Chamaesyce setiloba, a prostrate annual herb that grows to functionally fill a two-dimensional space. Number of leaves scaled slightly less than isometrically with total aboveground plant mass (α ≈ 0.9) and substantially less than isometrically with dry total stem mass (α = 0.82), showing reduced allocation to leaf as opposed to stem tissue with increasing plant size. Additionally, scalings of the lengths and radii of parent and daughter branches differed from those predicted for three-dimensional trees and shrubs. Unlike plants with typical three-dimensional architectures, C. setiloba has distinctive scaling relations associated with its particular prostrate herbaceous growth form.
许多动植物的特征与体型呈比例关系，这种关系可以用幂律方程 Y = βM(α)来描述，其中 Y 是生物体的一个属性，β是一个随属性变化的系数，M 是生物体大小的度量，α是另一个常数，即标度指数。在当前的模型中，经常观察到四分之一幂标度指数，据推测是由于分形样结构所致。然而，并非所有的植物或动物都符合这些模型的假设。因此，它们可能具有不同的标度关系。我们研究了一种这样的植物，Chamaesyce setiloba，这是一种匍匐的一年生草本植物，生长到能够充分占据二维空间。叶片数量与地上总植物质量的比例略小于等比（α≈0.9），与干总茎质量的比例远小于等比（α=0.82），表明随着植物大小的增加，叶片相对于茎组织的分配减少。此外，亲本和子枝的长度和半径的标度与三维树木和灌木的预测值不同。与具有典型三维结构的植物不同，C. setiloba 具有与其特定的匍匐草本生长形式相关的独特标度关系。
