|Kakani, V -|
|Boote, K -|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 7, 2010
Publication Date: N/A
Technical Abstract: Corn (Saturn Yellow) and grain sorghum (DeKalb 28E) plants were grown in pots in outdoor, sunlit controlled environment chambers in Gainesville, Florida. Seeds were sown on 14 September 2007, and plants were grown for 39 days after sowing (DAS). Pots were placed on ground-cloth covered soil in each chamber. Pots were watered to slight excess daily with drainage into the chamber soil. Carbon dioxide (CO2) concentrations (ppm or micromole/mole) were 360 ppm (ambient) and 720 ppm (double ambient). For each crop, two chambers were maintained at each CO2 level, with one continuously well watered and one designated for water-limited treatment (eight chambers). Inadvertently, some roots grew through pot drainage holes into the soil below the ground cloth. Beginning 10 October (26 DAS) water was withheld from pots in four chambers having each crop exposed to ambient or double-ambient CO2. Within 3 days, chamber evapotranspiration decreased drastically, but did not cease entirely, in all water-limited treatments. Canopy photosynthetic rates also decreased noticeably in water-limited, ambient CO2 chambers, but, unexpectedly, photosynthetic rates remained high in water-limited, double-ambient CO2 chambers. As a result, water-use efficiency (WUE) and radiation-use efficiency (RUE) of water-limited plants in elevated CO2 exceeded WUE and RUE of well-watered plants. These unanticipated results imply that C4 crop yields might be maintained high even with limited irrigation management in a future high CO2 world. Stomatal gas-exchange physiology needs more study.