Elevated tropospheric ozone concentration (O₃) significantly reduces photosynthesis and productivity in several C₄ crops including maize, switchgrass and sugarcane. However, it is unknown how O₃ affects plant growth, development and productivity in sorghum (Sorghum bicolor L.), an emerging C₄ bioenergy crop. Here, we investigated the effects of elevated O₃ on photosynthesis, biomass and nutrient composition of a number of sorghum genotypes over two seasons in the field using free‐air concentration enrichment (FACE), and in growth chambers. We also tested if elevated O₃ altered the relationship between stomatal conductance and environmental conditions using two common stomatal conductance models. Sorghum genotypes showed significant variability in plant functional traits, including photosynthetic capacity, leaf N content and specific leaf area, but responded similarly to O₃. At the FACE experiment, elevated O₃ did not alter net CO₂ assimilation (A), stomatal conductance (g_s), stomatal sensitivity to the environment, chlorophyll fluorescence and plant biomass, but led to reductions in the maximum carboxylation capacity of phosphoenolpyruvate and increased stomatal limitation to A in both years. These findings suggest that bioenergy sorghum is tolerant to O₃ and could be used to enhance biomass productivity in O₃ polluted regions.

中文翻译：

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生物能源高粱在臭氧浓度升高的情况下保持光合能力


对流层臭氧浓度 (O ₃ ) 升高会显着降低玉米、柳枝稷和甘蔗等多种 C ₄作物的光合作用和生产力。然而，O ₃如何影响高粱（ Sorghum bicolor L.）（一种新兴的C ₄生物能源作物）的植物生长、发育和生产力尚不清楚。在这里，我们使用自由空气浓缩富集 (FACE) 在田间和生长室中研究了两个季节中升高的 O ₃对多种高粱基因型的光合作用、生物量和营养成分的影响。我们还使用两种常见的气孔导度模型测试了 O ₃升高是否会改变气孔导度与环境条件之间的关系。高粱基因型在植物功能性状方面表现出显着的变异，包括光合能力、叶片氮含量和比叶面积，但对 O ₃的反应相似。在FACE实验中，升高的O ₃并没有改变净CO ₂同化( A )、气孔导度( g _s )、气孔对环境的敏感性、叶绿素荧光和植物生物量，但导致磷酸烯醇丙酮酸和磷酸烯醇丙酮酸的最大羧化能力降低。这两年A 的气孔限制增加。这些发现表明生物能源高粱对O ₃具有耐受性，可用于提高O ₃污染地区的生物质生产力。