Brassinosteroids: Fascinating Roles on Stomatal Mechanism, Physiological, and Anatomical Responses

Stomata control fundamental processes for crop development, such as carbon gain and water loss through transpiration. Understanding the processes involving brassinosteroid (BR) in regulating such structures can be an essential way to understand how plants control their physiological processes in defense of environmental stresses. Here, we will discuss the role of BR in stomatal regulation mechanisms and physiological benefits in plants under different types of abiotic stresses. BR negatively regulates stomatal development. Some studies suggest that drought tolerance responses involve increased BR levels, acting on stomatal closure. Stomatal regulation involving BR also involves other molecules at the cellular level, like hydrogen peroxide levels (H 2 O 2 ) and a direct relationship with starch metabolism. Exogenous application of BR in plants under different environmental stresses promoted improvements in physiological performance, like a vital control pathway in the balance between CO 2 gain and transpiration rate for plants under stress conditions.