Increased carbon uptake under elevated CO2 concentration enhances water-use efficiency of C4 broomcorn millet under drought

• Published in: Agricultural water management Vol. 245; p. 106631
• Main Authors: Zhang, Dongsheng, Li, Ali, Lam, Shu Kee, Li, Ping, Zong, Yuzheng, Gao, Zhiqiang, Hao, Xingyu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 28.02.2021
• Subjects: Antioxidative defense ability; Chlorophyll content; Evapotranspiration; Fluorescence; Photosynthesis; Fluorescence; Chlorophyll content; Photosynthesis; Antioxidative defense ability; Evapotranspiration
• ISSN: 0378-3774; 1873-2283
• DOI: 10.1016/j.agwat.2020.106631

Broomcorn millet (Panicum miliaceum L.) has been cultivated in arid or semi-arid area due to its high drought tolerance. Yet information on how elevated atmospheric CO2 concentration ([CO2]) affects the responses to drought of the productivity, photosynthesis, water-use efficiency and drought tolerance of broomcorn millet is lacking. We investigated the effects of elevated [CO2] and drought on gas exchange parameters, water-use efficiency, physiological indices related to drought tolerance, leaf area and aboveground biomass of broomcorn millet using an open-top chamber experimental facility in North China in 2015 and 2016. Broomcorn millet was grown in pots with or without drought stress under ambient or elevated [CO2]. Elevated [CO2] could compensate the negative effect of drought on the leaf area and aboveground biomass of broomcorn millet. This was attributed to the direct stimulation in photosynthesis due to increased carbon uptake under elevated [CO2]. Elevated [CO2] significantly enhanced the water-use efficiency of broomcorn millet at both leaf and plant levels, especially under drought condition. Elevated [CO2] did not significantly affect evapotranspiration, but increased water-use efficiency at the plant level by 15% (2015) and 35% (2016) of broomcorn millet under drought. Elevated [CO2] did not significantly affect PSII efficiency, antioxidative defense capacity (peroxidase, malondialdehyde) or osmotic adjustment (soluble sugar content and proline). We conclude that elevated [CO2] -induced increase in carbon uptake and water-use efficiency would increase the productivity of broomcorn millet in semi-arid areas under future high-CO2 climate. •Elevated CO2 concentration (E[CO2]) stimulated photosynthesis of broomcorn millet.•E[CO2] improved water-use efficiency of broomcorn millet, especially under drought.•E[CO2] did not improve antioxidative defense capacity of broomcorn millet.