Stomatal pores in the leaf surface are very likely to have played major importance during the evolution of land plants. The shoot of plants is normally covered by a waxy cuticle that prevents dehydration and thus allow them to survive in dry environments. Within this outer layer stomata can open to enable uptake of CO2 for synthesis and close to prevent excessive loss of water during dry spells. Consequently, stomata are commonly found in all aerial parts of vascular plants. In this project, we study how stomata evolved and obtained the ability to adapt the aperture of stomatal pores to changes in environmental conditions.
In non-vascular plants like mosses and hornworts, stomata are absent in the vegetative tissues that grow in moist environments. However, stomata often do occur in the sporophytes that grow on top of the vegetative tissue and protrude in the air. We will compare the properties of these stomata with those of fern and seed plants that appeared later during the evolution of land plants. The stomata of these evolutionary distant species will be tested for their ability respond to light and humidity. Thereafter the responsiveness of stomata will be linked to genes that are present in the respective species and are homologous to genes important for stomatal function in Arabidopsis. The project thus will link evolutionary changes in genes to the ability of plants to regulate CO2 uptake and water loss.