Cotton leaf expansion under high vapor pressure deficit

Overview

Rising atmospheric water demand poses a significant threat to crop productivity, with climate models projecting approximately 20% increases in average vapor pressure deficit (VPD) over the next 50 years. VPD is a measure of how much moisture the air can pull from plants, and higher values accelerate water loss and can limit leaf expansion and growth. This research collaboration seeks to evaluate cotton cultivar responses to extreme VPD conditions by leveraging controlled-environment facilities capable of simulating future climate scenarios.

The work builds on prior findings that certain cotton cultivars can restrict water loss under high VPD through early stomatal closure—a trait linked to shoot hydraulic conductance (Kshoot). Cultivars exhibiting this water-saving behavior have previously yielded 37% higher than standard checks under stress conditions. By comparing leaf expansion and physiological responses under low and extreme VPD environments, the research aims to identify cultivars best suited to maintain productivity under intensifying atmospheric demand.

Technical specifications

Research approach:

• Two-week-old cotton cultivars will be exposed to low VPD (0.5–1.5 kPa) and high VPD (>3.5 kPa) environments over a 14-day period
• Leaf expansion and transpiration rate (TR) will be monitored in separate experimental sets
• Stomatal activity and physiological responses will be compared between VPD treatments
• Cultivars with known variation in TR sensitivity to water deficit and high temperature will be evaluated
• Controlled-environment facilities (such as Biosphere 2/SAM) will be used to create extreme VPD conditions representative of future climate projections

Key performance metrics:

• Leaf expansion rate under varying VPD
• Transpiration rate sensitivity to atmospheric demand
• Stomatal closure timing and shoot hydraulic conductance (Kshoot)
• Water-saving potential across cultivars

Technology readiness level

This research is at an early-to-mid stage of validation. Prior laboratory and field studies have established baseline cultivar variation in TR sensitivity and demonstrated yield advantages of water-saving cultivars under stress. The next phase requires access to specialized controlled-environment facilities capable of generating extreme VPD conditions to validate findings under projected future climate scenarios. The research team is actively seeking facility partnerships to enable these validation experiments.