Increasing canopy photosynthesis in rice can be achieved without a large increase in water use-A model based on free-air CO2 enrichment
Increasing canopy photosynthesis in rice can be achieved without a large increase in water use-A model based on free-air CO2 enrichment
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DOI：
10.1111/gcb.13981
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发表时间：
2018-03-01
影响因子：
11.6
通讯作者：
Hasegawa, Toshihiro
中科院分区：
文献类型：
--
作者：
Ikawa, Hiroki;Chen, Charles P.;Hasegawa, Toshihiro
实现更高的冠层光合速率是增加未来作物产量的关键之一;然而，这通常需要额外的水投入，因为通过气孔的水分损失增加。低地水稻冠层目前消耗大量的水，用水量的任何进一步增加都可能严重影响当地的水资源。随着大气CO2浓度（[CO2]）上升等环境条件的变化，这种状况变得更加复杂。在这里，我们模拟和比较了一个高产水稻品种（Oryza sativa L。CV.高成）与一个共同的品种（CV。Koshihikari）在环境和高浓度[CO2]（A-CO2和E-CO2，分别）通过叶生理生态参数来自自由空气CO2富集（FACE）实验。在A-CO2和E-CO2条件下，高成的蒸散量均比越光高4%~ 5%，E-CO2使两品种的蒸散量降低4%~ 6%。因此，如果在未来的[CO2]条件下栽培高成，水的成本可以保持在与当前[CO2]条件下栽培越光相同的水平，冠层光合作用增加36%。敏感性分析表明，气孔导度是一个重要的生理因素，负责更大的冠层光合作用在高成越光。高成的气孔导度比越光高30%~ 40%，但由于高成在自然条件下具有较高的空气动力学阻力，冠层温度比越光低，导致蒸散量差异较小。尽管品种之间的蒸散量差异很小，但模型模拟显示，与越光相比，高成明显降低了行星边界层内的冠层和空气温度。我们的研究结果表明，低地水稻品种的特点是高气孔导度可以发挥关键作用，在未来几十年内，提高生产力和缓和热引起的损害粮食质量，而不显着增加作物用水。
Achieving higher canopy photosynthesis rates is one of the keys to increasing future crop production; however, this typically requires additional water inputs because of increased water loss through the stomata. Lowland rice canopies presently consume a large amount of water, and any further increase in water usage may significantly impact local water resources. This situation is further complicated by changing the environmental conditions such as rising atmospheric CO2 concentration ([CO2]). Here, we modeled and compared evapotranspiration of fully developed rice canopies of a high-yielding rice cultivar (Oryza sativa L. cv. Takanari) with a common cultivar (cv. Koshihikari) under ambient and elevated [CO2] (A-CO2 and E-CO2, respectively) via leaf ecophysiological parameters derived from a free-air CO2 enrichment (FACE) experiment. Takanari had 4%-5% higher evapotranspiration than Koshihikari under both A-CO2 and E-CO2, and E-CO2 decreased evapotranspiration of both varieties by 4%-6%. Therefore, if Takanari was cultivated under future [CO2] conditions, the cost for water could be maintained at the same level as for cultivating Koshihikari at current [CO2] with an increase in canopy photosynthesis by 36%. Sensitivity analyses determined that stomatal conductance was a significant physiological factor responsible for the greater canopy photosynthesis in Takanari over Koshihikari. Takanari had 30%-40% higher stomatal conductance than Koshihikari; however, the presence of high aerodynamic resistance in the natural field and lower canopy temperature of Takanari than Koshihikari resulted in the small difference in evapotranspiration. Despite the small difference in evapotranspiration between varieties, the model simulations showed that Takanari clearly decreased canopy and air temperatures within the planetary boundary layer compared to Koshihikari. Our results indicate that lowland rice varieties characterized by high-stomatal conductance can play a key role in enhancing productivity and moderating heat-induced damage to grain quality in the coming decades, without significantly increasing crop water use.