Water is the one ingredient that plants absolutely depend on. Farmers use
irrigation and other cultural practices to make the most of available
moisture, but crops are still vulnerable to heat and
[www.isaaa.org]
drought. Plants also lose water through transpiration, which accounts for
more than 98 percent of water taken up by plants.

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.

[ag.tennessee.edu].
aspx