Stomatal shape described by a superellipse in four Magnoliaceae species

ABSTRACT

Stomata are essential for the exchange of water vapour and atmospheric gases between vascular plants and their external environments. The stomatal geometries of many plants appear to be elliptical. However, prior studies have not tested whether this is a mathematical reality, particularly since many natural shapes that appear to be ellipses are superellipses with greater or smaller edge curvature than predicted for an ellipse. Compared with the ellipse equation, the superellipse equation includes an additional parameter that allows generation of a larger range of shapes. We randomly selected 240 stomata from each of four Magnoliaceae species to test whether the stomatal geometries are superellipses or ellipses. The stomatal geometries for most stomata (943/960) were found to be described better using the superellipse equation. The traditional “elliptical stomata hypothesis” resulted in an underestimation of the area of stomata, whereas the superellipse equation accurately predicted stomatal area. This finding has important implications for the estimation of stomatal area in studies looking at stomatal shape, geometry, and function.

KEYWORDS:

• curve fitting
• Magnoliaceae
• stomatal geometry
• stomatal area
• superellipse

Acknowledgments

We are very grateful to Yabing Jiao, Xingjian Liu, Lin Wang and Yufeng Yang for their valuable help during the preparation of this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All the raw data can be freely accessible on Dryad, a public repository (see Li et al. 2023, doi:10.5061/dryad.c866t1gc2).

Author contribution

Qiying Li: Writing − original draft (equal); Formal analysis (equal), Investigation (equal). Karl J. Niklas: Formal analysis; Supervision (equal); Writing – review & editing (lead). Ülo Niinemets: Formal analysis; Supervision (equal); Writing – review & editing (lead). Liuyue Zhang: Investigation (equal). Kexin Yu: Investigation (equal). Johan Gielis: Writing – review & editing (equal). Jie Gao: Writing – review & editing (equal). Peijian Shi: original draft (equal); Formal analysis (equal); Supervision (equal).

Additional information

Funding

Jie Gao was supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region [2022D01A213].