From one side to two sides: the effects of stomatal distribution on photosynthesis

Abstract

Abstract The functions of stomata have been studied for a long time; however, a clear understanding of the influences of stomatal distribution on photosynthesis, especially the CO 2 diffusion, is still unclear. Here, we investigated the stomatal morphology, distribution on leaf surfaces, vein traits and gas exchange parameters of 61 species, of which 29 were amphistomatous, spanning 32 families. Photosynthesis ( A ) was tightly coupled with operational stomatal conductance ( g s ) and mesophyll conductance ( g m ) regardless of whether phylogenetic relationships were accounted for. Although the enhancement of g s from ferns and gymnosperms to angiosperms could largely be explained by the increase in leaf vein density (VLA) and stomatal density (SD), the g s was decoupled from VLA and SD across angiosperm species. Instead, A in angiosperms was further influenced by the allocation of stomatal pores on leaf surfaces, which dramatically increased g s and g m . Moreover, the ratio of g s to anatomically based maximum g s was, on average, 0.12 across species. Our results show that the shift of stomatal pores from one leaf side to both sides played an important role in regulating CO 2 diffusion via both stomata and mesophyll tissues. Modifications of stomata distribution have potential as a functional trait for photosynthesis improvement.

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