Stomatal Cavity Modulates the Gas Exchange of Sorghum Bicolor (L.) Moench. Grown Under Different Water Levels

This work aimed to evaluate the effects of lower water levels on leaf intercellular spaces and to assess their relations with the gas exchange, anatomy, and growth of Sorghum bicolor. Experiments were conducted in a greenhouse, in which plants were subjected to three water conditions (ten replicates, n = 30): well-irrigated, decreased irrigation, and limited irrigation. Lower water levels had no significant effect on the growth of S. bicolor but increased the biomass of the roots. Moreover, the number of leaves, leaf area, and leaf size as well as the chlorophyll content were not affected by lower water levels, and no significant changes were detected for whole plant photosynthesis, transpiration, or stomatal conductance. The water content of the plants and the water potential remained unchanged. However, compared with other treatments, the decreased irrigation decreased water loss and increased the water retention. Lower water levels increased the intercellular CO percentage, mesophyll area, and proportion of stomatal cavities and promoted minor changes in leaf tissue and stomatal traits. The increased stomatal cavities provided higher CO uptake and prevented excessive water loss. Thus, modifications to the intercellular spaces promoted conditions to avoid excessive water loss while concurrently improving CO uptake, which are important traits for drought-tolerant plants.