Stomatal Crypts Have Small Effects on Transpiration: A Numerical Model Analysis

Stomata arranged in crypts with trichomes are commonly considered to be adaptations to aridity due to the additionaldiffusion resistance associated with this arrangement; however, information on the effect of crypts on gas exchange, relative tostomata, is sparse. In this study, three-dimensional Finite Element models of encrypted stomata were generated usingcommercial Computational Fluid Dynamics software. The models were based on crypt and stomatal architectural characteristicsof the species Banksia ilicifolia, examined microscopically, and variations thereof. In leaves with open or partially closedstomata, crypts reduced transpiration by less than 15% compared with nonencrypted, superficially positioned stomata. Alarger effect of crypts was found only in models with unrealistically high stomatal conductances. Trichomes inside the crypthad virtually no influence on transpiration. Crypt conductance varied with stomatal conductance, boundary layer conductance,and ambient relative humidity, as these factors modified the three-dimensional diffusion patterns inside crypts. It wasconcluded that it is unlikely that the primary function of crypts and crypt trichomes is to reduce transpiration.