Zhang Lirong, Wang Shiping, Yang Xiaoxia, Cui Xiaoyong, Niu Haishan
Department of Resources and Environment, Hebei Normal University for Nationalities, Chengde, China.
Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China.
Front Plant Sci. 2021 Apr 21;12:658702. doi: 10.3389/fpls.2021.658702. eCollection 2021.
A strong negative non-linear relationship exists between stomatal density (SD) and size (SS) or length (SL), which is of high importance in gas exchange and plant evolution. However, the cause of this relationship has not been clarified. In geometry, SD has an intrinsic relationship with SS or SL, which is defined as a geometric constraint here. We compiled global data to clarify the influence of this geometric constraint on the SD-SS relationship. The log-log scaling slope of the relationship between SD and SS and between SD and SL was not significantly different from -1 and -2, respectively. Although the non-geometric effect drove the SD-SS curve away from the power function with -1, a larger influence of the geometric constraint on SD was found. Therefore, the higher geometric constraint possibly causes the SD-SS relationship to be inevitably non-linear and negative. Compared to pteridophyta and gymnosperms, the geometric constraint was lower for angiosperm species, possibly due to most of them having smaller stomata. The relaxation of the geometric constraint seems to extend the upper range of SD in angiosperm species and hence enable them to exploit a wide range of environments.
气孔密度（SD）与大小（SS）或长度（SL）之间存在强烈的负非线性关系，这在气体交换和植物进化中具有高度重要性。然而，这种关系的成因尚未明确。在几何学中，SD与SS或SL存在内在关系，在此将其定义为一种几何约束。我们汇总了全球数据，以阐明这种几何约束对SD-SS关系的影响。SD与SS以及SD与SL之间关系的对数-对数缩放斜率分别与-1和-2无显著差异。尽管非几何效应使SD-SS曲线偏离了幂函数-1，但发现几何约束对SD的影响更大。因此，更高的几何约束可能导致SD-SS关系不可避免地呈非线性且为负相关。与蕨类植物和裸子植物相比，被子植物物种的几何约束较低，这可能是因为它们大多数气孔较小。几何约束的松弛似乎扩展了被子植物物种中SD的上限范围，从而使它们能够利用广泛的环境。
