Dovetailing the Genetic, Developmental and Functional Bases of the Adaptation of Stomatal Traits to Climate

Abstract

ABSTRACT Stomata, the micro‐valves on leaves, regulate CO2 uptake and water loss. Thus, the anatomical maximum stomatal conductance, g max, is a key influence on gas exchange, growth and productivity. For 145 geographically diverse ecotypes of Arabidopsis thaliana grown in a common garden we tested hypotheses for the drivers of variation in g max and a stomatal size‐density trade‐off, considering epidermal optimization, epidermal development and climate adaptation. Ecotypes native to colder and drier macroclimates had higher g max, consistent with leaf‐scale stress‐avoidance, despite having longer times to flowering. A high g max was achieved through greater epidermal allocation to stomata, via both increased guard cell initiation and smaller epidermal pavement cells. Stomatal traits showed polygenic associations with climate. A weak stomatal size‐density trade‐off was observed for only the abaxial surface, consistent with flexible constraints on stomatal development and independent trait adaptation. Dovetailing mechanisms influence stomatal adaptation to climate across a wide‐ranging species.