Temperature Effects on Vegetative and Reproductive Development of Peanut1,2

Optimum temperature for growth of most peanut ( Arachis hypogaea L.) genotypes is near 30°C. During the 1980 growing season, temperatures ranged from 35 to 40°C for many days in USA peanut producing regions, and severe crop losses attributable to the high temperatures and drought occurred. Experiments were initiated to determine the effect of temperature separate from drought on peanut development. Plants were grown in controlled environments at 30/25°C, 12/12 h light/dark temperatures to obtain a population of plants with uniform development. Measurements of individual leaf areas, leaf dry weights, and seedling height were made 21 days after planting to establish plant growth state. Then temperature treatments, based on temperatures expected to occur during the summer peanut growing season in the southwest USA, were begun. Temperature during the dark period was held constant at 22°C for all treatments. Temperatures during the light period were 30, 32, and 35°C. The 35°C treatment decreased individual leaf areas and dry weights at both 63 and 91 days after planting. Plants harvested at 91 days after planting showed reduced total leaf area and stem elongation was decreased in two experiments at 35°C. The highest temperature treatment significantly reduced the number of subterranean pegs. Mature seed weight was reduced and significantly so in two of three experiments, once for each cultivar tested. Thus, a temperature of 35°C was shown to have an inhibitory effect on peanut development even when plants were grown under well‐watered conditions. An evaluation of eight peanut genotypes showed genotypic variation in response to the 35°C temperature treatment. Selection for peanuts with improved heat tolerance may be possible.