Attempts to identify crop genetic material with larger growth stimulation at projected elevated atmospheric CO₂ concentrations are becoming more common. The probability of reductions in photosynthesis and yield caused by short-term variation in CO₂ concentration within elevated CO₂ treatments in the free-air CO₂ enrichment plots raises the question of whether similar effects occur in glasshouse or indoor chamber experiments. These experiments were designed to test whether even the normal, modest, cyclic variation in CO₂ concentration typical of indoor exposure systems have persistent impacts on photosynthesis and growth, and to explore mechanisms underlying the responses observed. Wheat, cotton, soybeans, and rice were grown from seed in indoor chambers at a mean CO₂ concentration of 560 μmol mol⁻¹, with “triangular” cyclic variation with standard deviations of either 4.5 or 18.0 μmol mol⁻¹ measured with 0.1 s sampling periods with an open path analyzer. Photosynthesis, stomatal conductance, and above ground biomass at 20 to 23 days were reduced in all four species by the larger variation in CO₂ concentration. Tests of rates of stomatal opening and closing with step changes in light and CO₂, and tests of responses to square-wave cycling of CO₂ were also conducted on individual leaves of these and three other species, using a leaf gas exchange system. Reduced stomatal conductance due to larger amplitude cycling of CO₂ during growth occurred even in soybeans and rice, which had equal rates of opening and closing in response to step changes in CO₂. The gas exchange results further indicated that reduced mean stomatal conductance was not the only cause of reduced photosynthesis in variable CO₂ conditions.

中文翻译：

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室内二氧化碳浓度的正常循环变化会减少叶子气体交换和植物生长。


尝试识别在预计升高的大气CO ₂浓度下具有更大生长刺激的作物遗传物质正变得越来越普遍。在自由空气CO ₂富集地块中，在升高的CO ₂处理中，CO ₂浓度的短期变化导致光合作用和产量降低的可能性提出了这样的问题：在温室或室内试验室实验中是否会发生类似的效应。这些实验旨在测试即使是室内暴露系统中典型的正常、适度、周期性的CO ₂浓度变化是否也会对光合作用和生长产生持续影响，并探索所观察到的反应背后的机制。小麦、棉花、大豆和水稻是在平均 CO ₂浓度为 560 μmol mol ^-1的室内室中从种子开始生长的，具有“三角”循环变化，用 0.1 s 测量的标准偏差为 4.5 或 18.0 μmol mol ^-1使用开路分析仪的采样周期。由于CO ₂浓度的较大变化，所有四个物种在20至23天时的光合作用、气孔导度和地上生物量均减少。使用叶气体交换系统，还对这些物种和其他三个物种的单片叶子进行了随着光和CO ₂阶跃变化的气孔打开和关闭速率的测试，以及对CO ₂方波循环的响应的测试。即使在大豆和水稻中，由于生长期间CO ₂循环幅度较大，气孔导度降低，它们响应CO ₂阶跃变化而具有相同的打开和关闭速率。 气体交换结果进一步表明，平均气孔导度降低并不是可变CO ₂条件下光合作用降低的唯一原因。