9. Sorghum

Sorghum (Sorghum bicolor L.) production systems encompass predominantly semiarid tropical regions of South Asia and Africa. Although sorghum is generally considered to be resilient when subjected to abiotic stresses, improved use of available soil water has the potential to increase yields. Substantial variation has been identified among sorghum genotypes in stomata closure both with early soil drying and elevated vapor pressure deficit. However, simulation study indicated that there would be little consistent impact on grain yield from early stomata closure with soil drying in the dryland areas in which sorghum is grown. Sensitivity to vapor pressure, on the other hand, could result in a high probability of consistent yield increase. Studies with sorghum lines expressing sensitivity of stomata closure to vapor pressure deficit showed linkages to plant hydraulic conductivity and aquaporin expression.