Effects of temperature on oil and protein concentration in soybean seeds cultured in vitro

Much of the economic value of soybean (Glycine max) is based on the amount of protein and oil produced in the seeds. To examine the influence of temperature on seed oil and protein concentration, immature soybean seeds (cv. Williams 82) were grown in vitro at temperatures of 17degreesC, 21degreesC, 25degreesC, 29degreesC and 33degreesC. Dry growth rate (DGR) was calculated to be maximal at 23.7degreesC. Oil and protein concentration and seed growth rate did not show statistical difference (P > 0.05) within the temperature range from 21-29degreesC. Across all temperatures, however, a quadratic regression on oil concentration (R-2 = 0.66) showed a minimum at 24.1degreesC and a quadratic regression on protein concentration (R-2 = 0.59) showed a minimum at 24.3degreesC. Dilution by increased dry matter accumulation in the seed accounted for much of the variation in oil and protein concentration and the two concentrations were equally affected across temperatures. Consequently, oil and protein concentrations were positively related over the tested range of temperature. It was concluded that under these conditions the rate of dry matter accumulation by soybean seeds was critical in influencing seed oil and protein concentrations.