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Recovering from Drought and Nitrogen Stress in CO2-Enriched Air
Zong, Y. and Shangguan, Z. 2014. CO2 enrichment improves recovery of growth and photosynthesis from drought and nitrogen stress in maize. Pakistan Journal of Botany 46: 407-415.

The authors note that within the context of the presumed increasing risk of extreme drought as a result of climate change associated with atmospheric CO2 enrichment, the evaluation of a crop's ability to recover and survive droughts requires further attention, which they thus proceed to provide in the case of maize.

What was done
Maize (Zea mays L. cv. Zhengdan 958) seedlings were hydroponically cultured in sand within two climate-controlled chambers; and when more than 80% of the seedlings fully expanded their first leaf, the chambers were programmed to have CO2 concentrations of either 380 or 750 ppm CO2 until the end of the study. And when more than 80% of the seedlings expanded their third leaves, they were irrigated with Hoagland solutions, "as well as different N solutions (5 mM N as the nitrogen deficiency treatment and 15 mM N as the control), and then the seedlings were allowed to grow for 25 days." On the 12th day under drought stress, however, the seedlings were re-watered at different levels, while "all relevant gas exchange and chlorophyll a fluorescence parameters of the seedlings were measured on the fifth day during their re-watering, and they were harvested on the sixth day during re-watering."

What was learned
The two Chinese scientists report that "maize seedlings suffering combined N limitation and drought had a better recovery of new leaf photosynthetic potential than those suffering only drought with ambient CO2." But they say that with elevated CO2, "the plants were able to maintain favorable water content as well as enhance their biomass accumulation, photochemistry activity, leaf water use efficiency and new leaf growth recoveries."

What it means
As a result of what they learned, Zong and Shangguan conclude that "elevated CO2 could help drought-stressed seedlings to maintain higher carbon assimilation rates under low water content," noting that such was the case "even under N-limited conditions, which allow the plants to have a better performance under drought following re-watering."

Reviewed 10 September 2014