Reproductive Growth, Development, and Yield Responses of Two Contrasting Soybean Cultivars to Temperature.

Temperature is a key factor in plant growth, development, and yield attributes. Soybean pod set and seed development is more susceptible to temperature stress leading to a considerable yield reduction. An experiment was conducted to investigate the temperature effects on two soybean cultivars with two different growth habits, determinate PR 5333 and indeterminate AG 5332. Plants grown in pots outdoors were moved into sunlit plant growth chambers at initial flowering stage and five day/night temperature regimes were imposed soon after flowering and continued until maturity. Plant growth and developmental parameters were recorded at frequent intervals. At maturity, plant-component dry weights, pod and seed numbers and dry weights were recorded. Significant temperature and cultivar differences were observed among many growth and developmental parameters measured. The time from flowering to pod maturity declined with the increase in temperature and quadratic functions best described the responses in both the cultivars. Time to seed maturity from flowering was higher in AG 5332 across the temperatures compared to PR 5333. The temperature optima for pod and seed number and dry weights were slightly lower than the temperature optima for total or vegetative biomass production. Also, the temperature optima for yield parameters were significantly different among the cultivars. The AG 5332 was high temperature tolerant when compared to PR 5333. The functional algorithms developed between soybean growth and developmental processes and temperature will be useful in improving soybean crop models for effective field management. Also, the knowledge of these relationships will be useful in assisting in-season pesticide and irrigation management decisions.