Stomatal behaviour under terminal drought affects post-anthesis water use in wheat

Area of Science:

• Agricultural Science
• Plant Physiology
• Crop Science

Background:

• Post-anthesis water availability is critical for wheat grain yield, directly impacting grain filling.
• Understanding genotypic differences in water uptake capacity, particularly from deeper soil layers, is crucial for developing drought-resilient wheat varieties.

Purpose of the Study:

• To investigate genotypic variations in root water uptake capacity from deeper soil profiles in wheat under terminal drought conditions.
• To compare the stomatal behavior and its influence on post-anthesis water use and grain yield between two contrasting wheat genotypes.

Main Methods:

• Wheat cultivars (Drysdale and IGW-3262) were grown in deep pots under controlled glasshouse conditions.
• Three post-anthesis watering treatments were applied: well-watered (WW), bottom-layer watering (WB), and water withheld (WS).
• Measurements included stomatal conductance, post-anthesis water use, water use efficiency, and grain yield.

Main Results:

• Post-anthesis water use in Drysdale remained consistent across WW and WB treatments.
• IGW-3262 exhibited a 30% reduction in water use in the WB treatment compared to WW, indicating impaired uptake from deeper layers.
• Faster stomatal closure in IGW-3262 under drying topsoil conditions in the WB treatment limited its root capacity for deeper water uptake.

Conclusions:

• Genotypic differences in stomatal regulation significantly influence post-anthesis water uptake from deeper soil profiles under terminal drought.
• The breeding line IGW-3262's rapid stomatal closure compromised its ability to utilize available subsoil moisture, leading to reduced grain yield.
• Drysdale demonstrated a greater capacity to maintain water uptake from deeper soil layers, highlighting its potential for drought adaptation.