Leakey Andrew D B, Uribelarrea Martin, Ainsworth Elizabeth A, Naidu Shawna L, Rogers Alistair, Ort Donald R, Long Stephen P
Institute for Genomic Biology , University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Plant Physiol. 2006 Feb;140(2):779-90. doi: 10.1104/pp.105.073957. Epub 2006 Jan 11.
While increasing temperatures and altered soil moisture arising from climate change in the next 50 years are projected to decrease yield of food crops, elevated CO2 concentration ([CO2]) is predicted to enhance yield and offset these detrimental factors. However, C4 photosynthesis is usually saturated at current [CO2] and theoretically should not be stimulated under elevated [CO2]. Nevertheless, some controlled environment studies have reported direct stimulation of C4 photosynthesis and productivity, as well as physiological acclimation, under elevated [CO2]. To test if these effects occur in the open air and within the Corn Belt, maize (Zea mays) was grown in ambient [CO2] (376 micromol mol(-1)) and elevated [CO2] (550 micromol mol(-1)) using Free-Air Concentration Enrichment technology. The 2004 season had ideal growing conditions in which the crop did not experience water stress. In the absence of water stress, growth at elevated [CO2] did not stimulate photosynthesis, biomass, or yield. Nor was there any CO2 effect on the activity of key photosynthetic enzymes, or metabolic markers of carbon and nitrogen status. Stomatal conductance was lower (-34%) and soil moisture was higher (up to 31%), consistent with reduced crop water use. The results provide unique field evidence that photosynthesis and production of maize may be unaffected by rising [CO2] in the absence of drought. This suggests that rising [CO2] may not provide the full dividend to North American maize production anticipated in projections of future global food supply.
预计未来50年气候变化导致的气温升高和土壤湿度改变会降低粮食作物产量，而二氧化碳浓度升高（[CO2]）则有望提高产量并抵消这些不利因素。然而，C4光合作用通常在当前的[CO2]水平下就已饱和，理论上在[CO2]升高时不应受到刺激。尽管如此，一些控制环境研究报告称，在[CO2]升高的情况下，C4光合作用和生产力会受到直接刺激，以及出现生理适应现象。为了测试这些效应是否会在露天环境和玉米带内出现，利用自由空气浓度增加技术，在环境[CO2]（376微摩尔/摩尔（-1））和升高的[CO2]（550微摩尔/摩尔（-1））条件下种植玉米（Zea mays）。2004年季节具有理想的生长条件，作物未经历水分胁迫。在没有水分胁迫的情况下，[CO2]升高时的生长并未刺激光合作用、生物量或产量。[CO2]对关键光合酶的活性或碳氮状态的代谢标志物也没有任何影响。气孔导度较低（-34%），土壤湿度较高（高达31%），这与作物水分利用减少一致。这些结果提供了独特的田间证据，即在没有干旱的情况下，玉米的光合作用和产量可能不受[CO2]升高的影响。这表明，[CO2]升高可能无法为未来全球粮食供应预测中预期的北美玉米生产带来全部益处。
