Avat Shekoofa, assistant professor with the University of Tennessee Department of Plant Sciences, said that identifying plant physiological traits that minimize the impact of drought appears to be the best bet in increasing yields under water deficit conditions. "One trait that shows great potential for conserving water among row crops is limited transpiration under high atmospheric vapor pressure deficit," he added.
Vapor pressure deficit (VPD) is the difference between the water vapor pressure inside the leaf and the water vapor pressure of the air at a certain temperature. When VPD is high, which typically occurs in the middle of the day, water transpires through plant tissue, specifically stomata. However, crops that exhibit the limited-transpiration trait will restrict transpiration during high VPD conditions by partially closing their stomata, thus conserving soil water levels for later use.
Shekoofa studied the response of transpiration rate with increasing VPD in several crop species, including soybean, corn, sorghum, and peanut. In a 2017 study at the West Tennessee AgResearch and Education Center, she tested six cotton cultivars for the expression of the limited transpiration trait and observed it in one (Phytogen 490 W3FE). This is the first time this trait has been observed in a commercially available cotton variety in the Mid-South.
For more details, read the news release from the University of Tennessee.