Roles of stomata in gramineous crops growth and biomass production

Stomata, microscopic pores surrounded by two guard cells, play essential roles in the most important plant physiological processes: photosynthesis and transpiration. Unlike dicotyledons, grasses, including major gramineous crops, have distinctive dumbbell-shaped guard cells and specialized subsidiary cells, forming a more efficient stomatal complex. Stomata are capable of governing growth, development, and biomass production by means of regulating the transpiration and gas exchange process in a plant; that is, the main functions of stomata are to permit CO 2 entry and control H 2 O movement and supply nutrients for biomass accumulation via photosynthesis. However, little is known about the roles of stomata in gramineous crops growth and biomass production. Stomatal conductance (gs) proves to be a vital aspect for high-yield potential in crops by influencing all the key traits of a crop's life cycle, particularly its biomass accumulation. Furthermore, transpiration enables stomata to stimulate biomass allocation in the phloem tissue, facilitating the translocation of assimilates and signals from the designated source to the sink, further endorsing floral transition and biomass allocation to the reproductive organs including the seed yield characteristic. This review focuses on stomatal function of gramineous crops, like rice, wheat, maize, barley, and so on. While stomata enforce majority of the essential processes in crops, their performance remains highly prone to the effects of unfavorable environmental conditions. Thus, manipulation of stomatal regulation is useful for the promotion of crop growth and biomass production.