Abstract
Root water uptake plays an important role in water transport and carbon cycle among Groundwater–Soil–Plant–Atmosphere–Continuum. The acclimation of crops under elevated carbon dioxide concentrations (eCO2) depends greatly on their capability to exploit soil water resources. Quantifying root water uptake and its relationship with crop growth under eCO2 remains challenging. This study observed maize growth subjected to current CO2 (400 ppm) and eCO2 (700 ppm) treatments via a device combined with a climate chamber and weighing lysimeters. Root water uptake patterns were determined based on the isotopic tracing technique. The main water uptake depth shifted from 0−20 cm under current treatment to 20−40 cm under eCO2 at the seedling growth stage. Maize took up 22.7% and 15.4% more soil water from a main uptake depth of 40−80 cm at jointing and tasseling stages in response to eCO2, respectively. More soil water (8.0%) was absorbed from the 80−140 cm layer at the filling stage under eCO2. Soil water contributions at the main uptake depth during seedling stage were negatively associated with leaf transpiration rate (Tr), net photosynthetic rate (Pn), and leaf area index (LAI) under both treatments, whereas significant positive correlations in the 40−80 cm layer under current treatment shifted to the 80−140 cm layer by eCO2. Deep soil water benefited to improve Tr, Pn and LAI under both treatments. No significant correlation between soil water contributions in each layer and leaf water use efficiency was induced by eCO2. This study enhanced our knowledge of crop water use acclimation to future eCO2 and provides insights into agricultural water management.
Highlights
Global food security is undergoing an increasing crisis, threatened by climate change
Soil water contributions at the main uptake depth during seedling stage were negatively associated with leaf transpiration rate (Tr ), net photosynthetic rate (Pn ), and leaf area index (LAI) under both treatments, whereas significant positive correlations in the 40−80 cm layer under current treatment shifted to the 80−140 cm layer by elevated CO2 (eCO2)
Our results demonstrated that increased CO2 concentration to 700 ppm shifted the water uptake depth of maize (Figure 6)
Summary
Global food security is undergoing an increasing crisis, threatened by climate change. Elevated atmospheric carbon dioxide concentrations (eCO2 ) have great impacts on water use, crop growth and yield [1,2,3]. Root water uptake is critical in water and carbon cycles in Groundwater–Soil–. Understanding the depth distribution and magnitude of root water uptake is important for planning irrigation and developing crop acclimation strategies to climate change [1,5]. The global CO2 concentration is predicted to reach 700 ppm by the end of the 21st century [6]. Maize is the most important food crop and is widely cultivated around the globe. Global demand for maize production is projected to double by 2050 facing a notable increase in CO2 [7,8].
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