Increasing frequency and severity of drought events is motivating development of novel and diverse approaches to improve crop productivity under water stress. During periods of water limitation, plants conserve water by closing their stomata. However, water conservation comes at the risk of lowered carbon gain, as CO2 uptake is closely coupled with H2O release through stomata. Along with plant directed morphological and biochemical acclimation to drier conditions, soil microbial communities can alleviate drought stress through various mechanisms, such as extending the rhizosphere zone of water depletion. The rapid nature of soil microbiome response to altered environmental conditions might provide an additional tool to improve drought resistance. To assess whether microbial communities can alleviate drought stress in corn (Zea mays), we measured changes in stomatal closure point (SCP, the leaf water potential at which stomatal conductance declines to 12% of the maximum) across plant ontogeny and between generations, and investigated correlations between SCP and physiological traits. We grew corn in a greenhouse and measured SCP after two, six, and eleven weeks. After eleven weeks, plants were harvested and the soil microbiome was used to inoculate a second generation of corn, which was grown for six weeks before subsequent SCP measurements.
Results/Conclusions
SCP varied greatly between plants, where the spread between the highest and lowest SCP was approximately 1 MPa. SCP in the first generation also varied with plant ontogeny. SCP was similar between the two and six week measurements; however, SCP declined after eleven weeks. The drop in SCP after eleven weeks may correlate with the life stage where stomata remain open at reproductive maturity as the plant dries and reaches the end of its life cycle. SCP had no correlation with plant height or root mass but had a positive correlation with turgor loss point i.e., the leaf wilting point. After six weeks of growth, SCP was lower for generation two compared to generation one. The declined SCP after one generation suggests that the microbiome may have shifted to increase drought tolerance, possibly due to pot-restricted water limitation or through microbial shifts in the reproductively mature plants’ soil. Generational differences in soil structure and nutrients could have also influenced the second generation toward lower SCP. These results improve our understanding of corn resistance to drought and suggest that rapid shifts in soil microbiome might increase drought tolerance by allowing maintenance of stomatal conductance under lower leaf water potentials.