Soil water status triggers CO₂ fertilization effect on the growth of winter wheat (Triticum aestivum)

Understanding the key processes and potential mechanisms of crops in response to elevated atmospheric CO2 concentration and drought may further shed lights on the impacts of climate change on the global agriculture ecosystems. This study examined the effects of elevated atmospheric CO2 concentration on the growth of winter wheat under different soil water conditions (full irrigation, mild water stress, moderate water stress, and severe water stress) with growth chambers where the CO2 concentration was controlled at 400 and 800 mu mol mol(-1) , respectively. We found a very strong CO2 fertilization effect on the growth of winter wheat under full irrigation condition, whereas this CO2 fertilization effect declined and eventually vanished with soil water stress, as evidenced by the decreased plant biomass and leaf photosynthesis of winter wheat independent of CO2 concentration. This adverse impact of water stress on the CO2 fertilization effect for plant growth may attribute to the changes in morphological characteristics of individual stoma and spatial distribution pattern of stomata as well as the non-structural carbohydrates of winter wheat. These results suggested that water stress may lower the CO2 fertilization effect on plant growth through altering stomatal traits, leaf photochemical processes, and biochemical compositions of winter wheat. Therefore, many current climate models based on earlier "double-CO2" experiment may overestimate the CO2 fertilization effect on crops, and meanwhile underestimate the impacts of climate change on global agriculture production when the elevated atmospheric CO2 concentration confounded with drought stress under future climate change.