Stomatal patterning and development in grasses

Abstract

Grass stomata provide an exemplary model of how form can improve functionality and promote the success of a plant family. The four-celled grass stomata are composed of dumbbell-shaped guard cells, each flanked by a single parallel subsidiary cell–arguably the most derived and fastest stomatal morphotype. The grasses' breathing pores develop in a strictly linear gradient within a stereotypically patterned epidermis, making it a highly accessible and spatiotemporally predictable developmental study system. Here, we highlight our current understanding of how vein-associated establishment of stomatal identity, tightly regulated asymmetric and symmetric cell division programs and extraordinary morphogenetic processes orchestrate the development of these uniquely shaped graminoid stomata. The innovative geometry and cellular composition of grass stomata have been repeatedly linked to rapid stomatal opening and closing kinetics, thus contributing to the grasses’ water-use-efficient photosynthesis. Therefore, besides revealing fundamental aspects of plant development and plant cell biology, the dissection of the developmental processes forming grass stomata can also highlight strategies to engineer stomatal morphology for improved plant-atmosphere gas exchange.