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Title: DIRECT EFFECTS OF ATMOSHPERIC CARBON DIOXIDE CONCENTRATION ON WHOLE CANOPY DARK RESPIRATION OF RICE

Author
item Baker, Jeffrey
item Allen Jr, Leon
item BOOTE, KENNETH - UNIVERSITY OF FLORIDA
item PICKERING, NIGEL - UNIVERSITY OF FLORIDA

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Global climate change involves rising levels of carbon dioxide in the earth's atmosphere. We conducted an experiment to test the effects of high levels of carbon dioxide and a wide range of air temperatures on nighttime dark respiration of rice plants. Rice was grown in outdoor plant growth chambers with daytime carbon dioxide treatments of 350 to 700 ppm. Respiration was measured across a wide range of both nighttime carbon dioxide concentrations and air temperatures. Nighttime respiration measurements were corrected for chamber leakage rates using a nitrous oxide leak detection system. Chamber leakage rate depended largely on both the inside and outside chamber carbon dioxide concentration. High carbon dioxide concentrations reduced respiration at temperatures above 21 C. Respiration increased with increasing temperature treatment and was always higher at night in the 700 ppm daytime treatment compared with that of the 350 ppm daytime treatment. These results indicate that both nighttime temperatures and carbon dioxide concentration of the air can affect respiration rates of rice plants.

Technical Abstract: The purpose of this study was to test for direct inhibition of rice canopy respiration by elevated atmospheric carbon dioxide concentration ([CO2]) across a range of short-term air temperature treatments. Rice (cv. IR-72) was grown in eight naturally sunlit, semi-closed, plant growth chambers at daytime [CO2] treatments of 350 and 700 ppm. Short-term nighttime air temperature treatments ranged from 21 to 40 C. Whole canopy respiration, expressed on a ground area basis (Rd), was measured at night by periodically venting the chambers with ambient air. This nighttime chamber venting and resealing procedure produced a range of increasing chamber [CO2] which we used to test for potential inhibitory effects of rising [CO2] on Rd. A nitrous oxide leak detection system was used to correct Rd measurements for chamber leakage rate (L) and also to determine if apparent reductions in nighttime Rd with rising [CO2] could be completely accounted for by L. The L was affected by both the chamber to ambient air CO2 concentration gradient and the inherent leakiness of each individual chamber. Even after correcting Rd for L, we detected a rapid and reversible, direct inhibition of Rd with rising chamber [CO2] for air temperatures above 21 C. This effect was larger for the 350 compared with the 700 ppm daytime [CO2] treatment and was also increased with increasing short-term air temperature treatments. These results suggest that naturally occurring diurnal changes in both ambient [CO2] and air temperature can effect Rd.