The 7th International CO2 Conference Web Site - Hazards of Temperature on Food Availability in Changing Environments (HOT-FACE)

by Leon Allen Jr.

Global temperatures are predicted to increase from rising levels of atmospheric carbon dioxide (CO₂) and other greenhouse gases. We conducted experiments in sunlit, controlled-environment chambers and temperature-gradient greenhouses to determine effects of elevated temperature and doubled CO₂ concentration on pollination and yield of rice, soybean, dry bean, peanut, and grain sorghum. Photosynthesis and vegetative growth were more tolerant of increasing temperatures than reproductive processes. Rice seed yields were optimum at 25°C mean daily temperature and decreased with increasing temperature (typically about 10% decline for each 1°C rise in temperature). Grain sorghum yield response to temperature was similar to rice, but dry bean was more sensitive, and soybean and peanut were more tolerant. Pollen viability followed a temperature response similar to seed yield. Comparisons of 43 rice cultivars in temperature-gradient greenhouses showed genetic variation in percent seed-set in response to a 4.5°C increase above ambient temperatures in Florida. Thus, there appears to be a range of adaptation of seed crops to temperature. Elevated CO₂ did not prevent high temperature decline in yield; in dry bean it made pollination more sensitive to high temperature. In summary, global warming will be a greater threat to crop seed yields than to photosynthesis and vegetative growth. However, crop genetic improvements might ameliorate part, but not all, of the high temperature hazards for seed yields and global food security.

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