Abstr-act. The embryonic axes of Spanish-type peanut seeds that do not exhibit dormancy to any extent were found to produce ethylene during germination. Virginia-type peanut seeds of the extremely dormant variety NC-13 produced low levels of ethylene when imbibed but not germinating. Treatments that released dormancy of NC-13 peanut seeds resulted in increas.ed ethylene production by the embryonic axis. Thz estimated internal concentration of ethylene in Virginia-type peanut seeds was 0.4 ppm at 24 hr of germination. Fumigation with an external concentration of 3.0 to 3.5 ppm for 6 hr was sufficient to break dormancy of Virginia-type peanut seeds. These results suggest that ethylene is associated with the germination processes of non-dormant seeds and participates in the breaking of seed dormancy of dormant peanut varieties.The p)rodulction of ethylene by germiinating oat (7), pea. (7) . and castor beaii ( l0) seeds, and Pci icillihon digitat urn spores (7) For germination studies a system patterned after that of Toole ct al. (11) was used for Virginia-type seeds. A system comparable to that described for Spanish-type seeds was also used. For Spanlish-type, 100 seeds were placed on filter paper in a 2 liter flask. One hundred ml of distilled water was added at the start of imbibition. After 16 hr of imbibition the excess water was decanted and 20 ml of distilled water added to maintain moist conditions. At eaclh 24 hr interval whleln germination was determined, a freshi 20 ml aliquiot of distilled water was added to each flask. Seeds were incubated at 280 in the dark for both ethylene and germination studies.Sealed flasks kept in the dark for about 6 lhr were sampled for ethylene by withdrawinig 10 ml of the gas phase. Not more than 20 seeds nor more than 100 seeds were used per 250 ml and 2000 ml flasks, respectively (see

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.

Improved drought tolerance of some crops has been associated with extensive root systems. Since peanut (Arachis hypogaea L.) is grown in many arid and semiarid regions, this study was done to determine if peanut genotypes differed in extent of root growth (volume and dry weight). A method to estimate root growth potential of peanut by measuring root volumes was developed and used to make comparisons among peanut genotypes. Plants were grown in the greenhouse for 46 to 49 days in PVC tubes (10.2 cm i.d, and 76.2 cm in length) containing fritted clay. Plants were fertilized twice weekly with 200 ml of modified Hoagland solution and watered twice daily. Comparisons of growth were made among and within virginia, spanish, and valencia botanical type peanut. Genotypes differed in both root (volume and dry weight) and shoot (height, dry weight, leaf area, and leaf number) characteristics. Root volume and dry weight were highly correlated among the entries tested. Shoot dry weight, leaf area, and number of leaves were significantly correlated in most tests. Root dry weight and volume were positively correlated with shoot dry weight, leaf area, and number of leaves, but not necessarily with all of these parameters in every test. The data indicate strong coordination between aerial and subterranean growth and considerable diversity in root volume. The differences among entries in this limited sample of peanut germplasm suggest selections for more extensive rooting traits is feasible for this crop and may prove useful for developing more drought tolerant peanut cultivars.