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CO₂ ENRICHMENT IMPROVES RECOVERY OF GROWTH AND PHOTOSYNTHESIS FROM DROUGHT AND NITROGEN STRESS IN MAIZE

YUZHENG ZONG^1,2 AND ZHOUPING SHANGGUAN^2*

Abstract: In the context of the increasing risk of extreme drought as a result of climate change and increasing CO₂ in the future of northwest China, evaluation of crops’ ability to recover and survive droughts requires further attention. To test the effects of re-watering on plants suffering water and nitrogen limitations in the presence of elevated CO₂, maize (Zea mays) was planted to experience combined elevated CO₂ (380 or 750 µmolmol^-1, climate chamber), water stress (15% PEG-6000) and nitrogen limitation (5 or 15mM N in Hoagland solutions) and then re-watered at three levels (300mL, 600mL, 900mL per pot of distilled water). When plants were re-watered, drought stressed and N limited plants with ambient CO₂ increased their water content more than that of elevated CO₂, while the enhancement of growth rate were negatively related to the increasing plant water content. Elevated CO₂ could help re-watered seedlings to have higher photosynthetic capacity (F_v/F_m, Φ_PSII, P_n,P_n/T_r and P_n/G_s) and new leaf growth under low water content, apart from nitrogen deficiency. The results demonstrated that elevated CO₂ could help drought stressed seedlings to maintain higher carbon assimilation rates under low water content, as a result to improve leaf water use efficiency.

¹College of Agriculture, Shanxi Agricultural University, 030801 Taigu, Shanxi, People’s Republic of China

²State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, 712100 Yangling, Shaanxi, People’s Republic of China

*Corresponding author: shangguan@ms.iswc.ac.cn, Tel: 086-29-87019107, Fax: 086-29-87012210.