An Intrinsic Geometric Constraint on Morphological Stomatal Traits

Lirong Zhang; Shiping Wang; Xiaoxia Yang; Xiaoyong Cui; Haishan Niu

doi:10.3389/fpls.2021.658702

An Intrinsic Geometric Constraint on Morphological Stomatal Traits

Front Plant Sci. 2021 Apr 21:12:658702. doi: 10.3389/fpls.2021.658702. eCollection 2021.

Authors

Lirong Zhang^{1

2

3}, Shiping Wang^{2

4

5}, Xiaoxia Yang^{6

7}, Xiaoyong Cui⁸, Haishan Niu³

Affiliations

¹ Department of Resources and Environment, Hebei Normal University for Nationalities, Chengde, China.
² Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China.
³ College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China.
⁴ CAS Center for Excellence in Tibetan Plateau Earth Science of the Chinese Academy of Sciences, Beijing, China.
⁵ Naqu Integrated Observation and Research Station of Ecology and Environment, Tibet University and Institute of Tibetan Plateau Research of the Chinese Academy of Sciences, Lasa, China.
⁶ State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xining, China.
⁷ Qinghai Provincial Key Laboratory of Adaptive Management on Alpine Grassland, Qinghai University, Xining, China.
⁸ College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China.

Abstract

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^-1 or SL^-2, 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.

Keywords: geometric constraint; plant evolution; stomatal density; stomatal index; stomatal length.