Résumé
Hydathodes are specialized structures found in many plant species, typically located at the tips of leaves and leaf serrations. They consist of xylem cells diving into a cluster of small inner cells, collectively known as the epithem, which lies beneath large, stomata-like cells called hydathode pores. Unlike regular stomata, hydathode pores never totally close, enabling guttation-the exudation of xylem-derived fluids-particularly when stomatal tran-spiration is limited. This process helps prevent excessive water accumulation in the leaf's intercellular spaces, also called leaf flooding, which could otherwise hinder photosynthesis. Consequently, hydathodes may play a crucial role in regulating water movement within plants and impact photosynthesis. However, their development remains poorly understood, as does their precise function in plant physiology, largely due to the absence of known mutants with disrupted hydathode function.</p><p>Here, we will report that hydathode formation in Arabidopsis thaliana is independent of leaf serration. Furthermore, we present a molecular and genetic framework governing hydathode development. Our findings indicate that differential regulation of the cell cycle contributes to the formation of both small epithem cells and large hydathode pores. Notably, we identify several mutants with impaired hydathode formation that exhibit environmentally induced leaf flooding. We characterize this flooding phenomenon and provide preliminary insights into its effects on leaf physiology and photosynthesis.</p></div>