Response of crop photosynthetic product allocation under different water supply conditions: A global synthetic analysis

Context or problem

Photosynthetic product allocation is essential for crop development, but the rising frequency of extreme drought and flood events has disrupted biomass distribution and carbon storage in terrestrial ecosystems. Yet, the effects of seasonal drought stress on crop biomass allocation remain poorly understood.

Objective or research question

This study aims to quantitatively assess how drought stress influences the allocation patterns of photosynthetic products in maize and wheat, with particular attention to biomass partitioning and its implications for soil carbon dynamics and water use efficiency.

Methods

To address this gap, we conducted a meta-analysis and regression analysis based on 63 peer-reviewed studies comparing photosynthetic product allocation under well-watered (WW) and drought stress (DS) conditions in maize and wheat. We then employed regression analysis to explore the response of crop photosynthetic product allocation to water stress.

Results

Drought stress inhibits crop growth, crops allocate more biomass to their roots, resulting in a significant increase in the root to shoot ratio. Compared with wheat, maize demonstrates greater drought adaptability to water stress by allocating more photosynthetic products to its roots. Maize shows enhanced growth and water use efficiency under moderate to high water supply (300–800 mm), whereas wheat performs steadily under moderate water supply (300–650 mm).

Conclusions

Water availability strongly influences crop biomass allocation and water use efficiency. Drought promotes root-biased allocation, potentially increasing soil carbon input, which could increase organic carbon accumulation in soils. For optimal yield and root-derived carbon sequestration, moderate to high water supply is recommended for maize, while wheat benefits from a moderate supply to avoid the negative effects of overwatering.

Implications or significance

These findings revealed the significant effects of water supply on crop photosynthetic product allocation and water use efficiency, which can help optimize field management to improve crop productivity and irrigation efficiency.