Abstract Understanding the processes and mechanisms of crops in response to elevated CO2 concentration and water stress is critical for accurately projecting the potential risk of climate change on global agriculture productivity. We examined effects of elevated CO2 concentration on plant growth, stomatal traits, leaf gas exchange, and biochemistry of bell peppers under water stresses with environmental growth chambers controlling CO2 concentration at ambient (400 μmol mol−1) or elevated (800 μmol mol−1) CO2 level along a soil water gradient including full irrigation (75–85 % FC), mild water stress (65–75 % FC), moderate water stress (55–65 % FC), and severe water stress (45–55 % FC). We found that rising atmospheric CO2 concentration dramatically enhanced the plant biomass of bell peppers through the strong CO2 fertilization effect even under the mild and moderate water stresses. The CO2 fertilization effect on plant growth under water stress was directly confirmed by the boosted leaf photosynthesis, which can be attributed to the increased stomatal number and the larger stomatal openness as well as the more regular spatial distribution patterns of bell pepper plants grown at high CO2 concentration and water stress. As a result, the leaf-level water use efficiency was enhanced due to the stimulated leaf photosynthesis and the reduced leaf transpiration under high CO2 concentration, even for these bell pepper plants are suffering water stresses. Nevertheless, this CO2 fertilization effect on plant growth and leaf photosynthesis were generally decreased along the soil water gradients, indicating that the CO2 fertilization effect may partially be mitigated or even offset by water availability as evidenced by the little impact of high CO2 concentration on the total biomass of pepper plants under severe water stress. Our results suggest that water stress may lower the CO2 fertilization effect on plant growth of bell pepper plants, thus current ecological processes models based on the strong CO2 fertilization effect may overestimate the benefits of plants from future rising CO2 concentration, and meanwhile underestimate the potential risk of climate change on global agricultural productivity, where elevated CO2 concentration is usually accompanied by regional drought events.

中文翻译：

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土壤水分胁迫下二氧化碳施肥对植物生长的影响与甜椒（Capsicum annuum L.）的气孔性状、叶片光合作用和叶面氮的变化有关

摘要 了解作物应对二氧化碳浓度升高和水分胁迫的过程和机制对于准确预测气候变化对全球农业生产力的潜在风险至关重要。我们通过环境生长室控制环境 (400 μmol mol−1) 或升高 (800 μmol mol−1) 的 CO2 浓度，研究了 CO2 浓度升高对植物生长、气孔性状、叶片气体交换和水分胁迫下的生物化学的影响) 土壤水分梯度的 CO2 水平，包括充分灌溉 (75-85 % FC)、轻度缺水 (65-75 % FC)、中度缺水 (55-65 % FC) 和严重缺水 (45-55 %) FC）。我们发现，即使在轻度和中度水分胁迫下，大气中 CO2 浓度的升高也会通过强大的 CO2 施肥效应显着提高甜椒的植物生物量。CO2 施肥对水分胁迫下植物生长的影响直接通过叶片光合作用的增强得到证实，这可归因于气孔数量增加和气孔开放度更大，以及在高 CO2 下生长的甜椒植物的空间分布格局更规则浓度和水分压力。因此，即使这些甜椒植物正遭受水分胁迫，在高 CO2 浓度下，由于刺激的叶片光合作用和减少的叶片蒸腾作用，叶片水平的水分利用效率得到提高。尽管如此，这种 CO2 施肥对植物生长和叶片光合作用的影响通常沿着土壤水分梯度下降，表明 CO2 施肥效应可能会被水分可用性部分减轻甚至抵消，这一点可以通过高 CO2 浓度对总生物量的影响很小来证明。严重水分胁迫下的辣椒植物。我们的研究结果表明，水分胁迫可能会降低 CO2 施肥对甜椒植物生长的影响，因此目前基于强 CO2 施肥效应的生态过程模型可能高估了未来 CO2 浓度升高对植物的益处，同时低估了潜在风险气候变化对全球农业生产力的影响，其中二氧化碳浓度升高通常伴随着区域干旱事件。