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

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 (Fv/Fm, ΦPSII, Pn,Pn/Tr and Pn/Gs) 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.