Abstract
Global climate change, especially, increases in carbon dioxide (CO 2) concentration and the associated increases in temperature will have significant impact on the crop production. Grain-sorghum [ Sorghum bicolor (L.) Moench] cultivar DeKalb 28E was grown at daytime maximum/nighttime minimum temperature regimes of 32/22, 36/26, 40/30 and 44/34 °C at ambient (350 μmol CO 2 mol −1) and elevated (700 μmol CO 2 mol −1) CO 2 from emergence to maturity in controlled environments to quantify the effects of temperature and CO 2 on the reproductive processes and yield. Growth temperatures of 40/30 and 44/34 °C inhibited panicle emergence. Growth temperatures ≥36/26 °C significantly decreased pollen production, pollen viability, seed-set, seed yield and harvest index when compared to 32/22 °C. Percentage decreases in pollen viability, seed-set, seed yield and harvest index due to elevated temperature were greater at elevated CO 2 when compared with ambient CO 2. Elevated CO 2 increased seed yield (26%) at 32/22 °C, but decreased seed yield (10%) at 36/26 °C. At high temperatures, elevated CO 2 increased vegetative growth but not seed yield, thus, leading to decreased harvest index. We conclude that the adverse effects of elevated temperature on reproductive processes and yield of grain-sorghum were more severe at elevated CO 2 than at ambient CO 2; and the beneficial effects of elevated CO 2 decreased with increasing temperature. The adverse temperature sensitivity of reproductive processes and yield at elevated CO 2 was attributed to higher canopy foliage and seed temperatures.
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