|Allen, Leon - Hartwell|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2009
Publication Date: N/A
Citation: N/A Interpretive Summary: none
Technical Abstract: Maize and grain sorghum were grown for 39 d in sunlit environment-controlled chambers at 360 (ambient) and 720 (double-ambient, high) µmol mol-1 [CO2]. The most enhancement by high [CO2] on canopy photosynthesis (Pg), measured at 1,200 µmol m-2 s-1 solar PPFD, occurred at early plant growth stage, 17-22 d after seed planting (DAP), when increases in Pg by high [CO2] were 5-22% for maize and 27-95% for sorghum. Drought stress, which was imposed at 26 DAP and became evident at 28-34 DAP for maize and 30-36 DAP for sorghum, caused Pg declines of 54-84% and 29-46% at ambient [CO2] and 17-31% and 1-20% at high [CO2] for the stressed maize and sorghum, respectively. The water-use efficiency (expressed as mmol [CO2] mol-1 H2O) during the drought-evident periods averaged 5.4, 3.4, 6.9 and 11.2 for maize, compared with 5.5, 6.6, 7.5 and 19.8 for sorghum, for the ambient-[CO2] well-watered, ambient-[CO2] stressed, high-[CO2] well-watered and high-[CO2] stressed plants, respectively. Although growth analyses of the young developing plants, performed at 34 DAP for maize and 39 DAP for sorghum, did not reveal a clear-cut difference in biomass between the ambient-[CO2] and high-[CO2] well-watered plants, above-ground dry weights of the ambient-[CO2] stressed plants were 70% for maize and 80% for sorghum, when compared with the high-[CO2] stressed plants. Thus, maize and sorghum used water more efficiently at high [CO2], and both plants grew better at high [CO2] than their counterparts at ambient [CO2] in the presence of drought.