Viewing stomata in action: Autonomous in planta imaging of individual stomatal movement links morphology and kinetics

Stomata regulate plant gas exchange with the environment, balancing between water loss and CO ₂ uptake. Gas exchange dynamics are influenced by traits such as stomatal morphology, size and density, which are commonly investigated using imprints and manual microscopy, methods that are destructive and time consuming. Moreover, these microscopic properties are statically sampled and related to the dynamic ensemble behavior: gas exchange of an entire plant or part of a leaf. Knowledge on how morphology, size and density of stomata influence the movement of individual stomata is limited. We developed a compact microscope system that can measure the kinetics of tens of stomata in vivo simultaneously, with sub-minute time resolution. The system can be deployed in the plant’s growth environment, at minimal impact on leaf microclimate. The characteristics of our microscope and data analyses are described, and we demonstrate its capabilities on Chrysanthemum morifolium with novel insight into individual stomata’s contribution to water-use efficiency.