The Interrelationship Between Water Use Efficiency and Radiation Use Efficiency Under Progressive Soil Drying in...

Area of Science:

• Agricultural Science
• Plant Physiology
• Ecology

Background:

• Maximizing water use efficiency (WUE) and radiation use efficiency (RUE) is crucial for dryland farming.
• The association between WUE and RUE under water scarcity is not fully understood.

Purpose of the Study:

• To investigate the relationship between WUE and RUE in maize under varying water availability.
• To elucidate the underlying mechanisms of WUE and RUE interactions during drought stress.

Main Methods:

• A two-year field trial with maize subjected to five progressive soil drying regimes at early (three-leaf) and late (seven-leaf) growth stages.
• Measurement of environmental variables and maize growth traits at leaf and canopy levels.
• Analysis of aboveground biomass (AGB), leaf area index (LAI), fraction of absorbed photosynthetically active radiation (fAPAR), and light extinction coefficient (k).

Main Results:

• Leaf WUE increased with drought at the early stage but decreased at the later stage. Leaf RUE consistently decreased with drought.
• Water deficits significantly reduced AGB, LAI, fAPAR, and k regardless of drought timing.
• A positive linear WUE-RUE relationship was observed under early-stage drought, while a negative relationship occurred under late-stage drought.
• Canopy WUE and RUE interaction was more influenced by fAPAR than LAI.

Conclusions:

• The relationship between WUE and RUE in maize is dynamic and dependent on the timing of water deficit.
• fAPAR plays a critical role in mediating the interaction between water and radiation use under drought conditions.
• Findings offer new insights into optimizing water and radiation use in dryland agriculture and highlight the importance of fAPAR in drought impact assessments.