|Allen, Leon - Hartwell|
Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2006
Publication Date: 10/12/2006
Citation: Prasad, P.V.V., Boote, K.J., Allen Jr, L.H. 2006. Adverse high temperature effects on pollen viability, seed-set, seed yield and harvest index of grain-sorghum [Sorghum bicolor (L.) Moench] are more severe at elevated carbon dioxide due to higher tissue temperatures. Agricultural and Forest Meteorology. 139:237-251. Interpretive Summary: Projected global warming associated with rising CO2 could hurt reproductive growth and seed yields of grain sorghum. ARS and University of Florida scientists tested the combined effects of doubled CO2 and elevated temperature on pollen production and viability, seed-set, and seed yield of the grain sorghum cultivar DeKalb 28E. Plants were grown at 350 (ambient)and 700 (elevated) ppm CO2 and maximum/minimum temperatures of 32/22, 36/26, 40/30, and 44/34 degrees C (90/72, 97/79, 104/86, and 111/93 degrees F). High temperatures of 111/93 F and even 104/86 F prevented emergence of seed-heads. Temperatures greater than 97/79 F decreased all aspects of reproductive growth, and decreases were more severe at elevated CO2 than ambient CO2. Plant height decreased from 90/72 F to 111/93 F, but the number of leaves increased, because the phase of growth never shifted from vegetative to reproductive. Thus, elevated temperatures could decrease yields and change vegetative growth patterns of grain sorghum. This information forewarns other scientists of the detriments of potential global warming, and points out the need for plant breeding and cultivar selections that would ameliorate the impact of high temperatures.
Technical Abstract: Increases in carbon dioxide (CO2) and anticipated global warming will impact crop production. Grain-sorghum [Sorghum bicolor (L.) Moench] cultivar DeKalb 28E was grown at cyclic maximum/minimum temperatures of 32/22, 36/26, 40/30, and 44/34C at 350 (ambient) and 700 ppm CO2 to quantify CO2 and temperature effects on five reproductive processes (production and viability of pollen, seed-set, seed yield, and harvest index). Temperatures of 40/30 and especially 44/34C inhibited panicle emergence. Temperature > 36/26C decreased all aspects of reproduction compared to 32/22C. Percentage decreases due to elevated temperature were greater at elevated CO2 than ambient CO2, indicating negative interactions. Elevated CO2 increased seed yield at 32/22C, but decreased it at 36/26C. Plant height and internode lengths decreased linearly from 32/22 to 44/34C, whereas the number of leaf nodes increased linearly. Adverse effects of elevated temperature on reproductive processes and yield were more severe at elevated than ambient CO2; and the beneficial effects of elevated CO2 decreased with increasing temperature. The adverse temperature sensitivity of reproductive processes and yield at elevated CO2 was attributed to higher canopy foliage and seed temperatures.