The physiological importance of developmental mechanisms thatenforce proper stomatal spacing in Arabidopsis thaliana

摘要

Genetic and cell biological mechanisms that regulate stomatal development are necessaryto generate an appropriate number of stomata and enforce a minimum spacing of one epidermalcell between stomata. The ability to manipulate these processes in a model plant systemallows us to investigate the physiological importance of stomatal patterning and changes indensity, therein testing underlying theories about stomatal biology. Twelve Arabidopsis thaliana genotypes that have varied stomatal characteristics as a resultof mutations or transgenes were analyzed in this study. Stomatal traits were used to categorizethe genotypes and predict maximum stomatal conductance to water vapor (Anatomicalgsmax) for individuals. Leaf-level gas-exchange measurements determined Diffusive gsmax, netcarbon assimilation (A), water-use efficiency (WUE), and stomatal responses to increasingCO2 concentration. Genotypes with proper spacing (< 5% of stomata in clusters) achieved Diffusive gsmax valuescomparable to Anatomical gsmax across a 10-fold increase in stomatal density, while lines withpatterning defects (> 19% clustering) did not. Genotypes with clustering also had reduced Aand impaired stomatal responses, while WUE was generally unaffected by patterning. Consequently, optimal function per stoma was dependent on maintaining one epidermalcell spacing and the physiological parameters controlled by stomata were strongly correlatedwith Anatomical gsmax.