United States Department of Agriculture - Agricultural Research service, Center for Medical, Agricultural and Veterinary Entomology, Chemistry Research Unit, 1600/1700 SW 23rd Drive, Gainesville, FL 32608-1069, USA.
J Plant Physiol. 2011 Nov 1;168(16):1909-18. doi: 10.1016/j.jplph.2011.05.005. Epub 2011 Jun 14.
Maize and grain sorghum seeds were sown in pots and grown for 39 days in sunlit controlled-environment chambers at 360 (ambient) and 720 (double-ambient, elevated)μmol mol(-1) carbon dioxide concentrations [CO(2)]. Canopy net photosynthesis (PS) and evapotranspiration (TR) was measured throughout and summarized daily from 08:00 to 17:00h Eastern Standard Time. Irrigation was withheld from matched pairs of treatments starting on 26 days after sowing (DAS). By 35 DAS, cumulative PS of drought-stress maize, compared to well-watered plants, was 41% lower under ambient [CO(2)] but only 13% lower under elevated [CO(2)]. In contrast, by 35 DAS, cumulative PS of drought-stress grain sorghum, compared to well-watered plants, was only 9% lower under ambient [CO(2)] and 7% lower under elevated [CO(2)]. During the 27-35 DAS drought period, water use efficiency (WUE, mol CO(2)Kmol(-1)H(2)O), was 3.99, 3.88, 5.50, and 8.65 for maize and 3.75, 4.43, 5.26, and 9.94 for grain sorghum, for ambient-[CO(2)] well-watered, ambient-[CO(2)] stressed, elevated-[CO(2)] well-watered and elevated-[CO(2)] stressed plants, respectively. Young plants of maize and sorghum used water more efficiently at elevated [CO(2)] than at ambient [CO(2)], especially under drought. Reductions in biomass by drought for young maize and grain sorghum plants were 42 and 36% at ambient [CO(2)], compared to 18 and 14% at elevated [CO(2)], respectively. Results of our water stress experiment demonstrated that maintenance of relatively high canopy photosynthetic rates in the face of decreased transpiration rates enhanced WUE in plants grown at elevated [CO(2)]. This confirms experimental evidence and conceptual models that suggest that an increase of intercellular [CO(2)] (or a sustained intercellular [CO(2)]) in the face of decreased stomatal conductance results in relative increases of growth of C(4) plants. In short, drought stress in C(4) crop plants can be ameliorated at elevated [CO(2)] as a result of lower stomatal conductance and sustaining intercellular [CO(2)]. Furthermore, less water might be required for C(4) crops in future higher CO(2) atmospheres, assuming weather and climate similar to present conditions.
在 360（环境）和 720（双环境，升高）μmol mol(-1) 二氧化碳浓度 [CO(2)] 的阳光充足的控制环境室内，将玉米和高粱种子播种在盆中，并生长 39 天。从东八区 08:00 到 17:00 测量整个冠层净光合（PS）和蒸腾（TR），并进行每日总结。从播种后 26 天（DAS）开始，将配对处理的灌溉量减少。与水分充足的植株相比，在环境 [CO(2)] 下，干旱胁迫玉米的累积 PS 在 35 DAS 时降低了 41%，但在升高的 [CO(2)] 下仅降低了 13%。相比之下，在 35 DAS 时，与水分充足的植株相比，干旱胁迫高粱的累积 PS 在环境 [CO(2)] 下仅降低了 9%，在升高的 [CO(2)] 下降低了 7%。在 27-35 DAS 干旱期间，水分利用效率（WUE，mol CO(2)Kmol(-1)H(2)O）分别为 3.99、3.88、5.50 和 8.65，用于玉米和 3.75、4.43、5.26 和 9.94，用于高粱，分别用于环境-[CO(2)]水分充足、环境-[CO(2)]胁迫、升高-[CO(2)]水分充足和升高-[CO(2)]胁迫的植株。与环境 [CO(2)] 相比，在升高的 [CO(2)] 下，玉米和高粱幼株的水分利用效率更高，尤其是在干旱条件下。与在升高的 [CO(2)] 下相比，在环境 [CO(2)] 下，幼玉米和高粱植株的生物量因干旱而减少了 42%和 36%，分别为 18%和 14%。我们的水分胁迫实验结果表明，在蒸腾速率降低的情况下，维持相对较高的冠层光合速率提高了在升高的 [CO(2)] 下生长的植物的 WUE。这证实了实验证据和概念模型，即面对减少的气孔导度，细胞间 [CO(2)] 的增加（或持续的细胞间 [CO(2)]) 导致 C(4) 植物的生长相对增加。简而言之，由于气孔导度降低和维持细胞间 [CO(2)]，在升高的 [CO(2)] 下，C(4) 作物的干旱胁迫可以得到缓解。此外，假设天气和气候与目前条件相似，未来在更高的 CO(2) 大气中，C(4) 作物可能需要更少的水。
