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

Temperature is the major factor affecting many developmental, growth, and yield attributes of crops. In spite several studies in the past, soybean plant processes and temperature relationships are not available under realistic radiation environments. An experiment was conducted to investigate temperature effects on two different cultivars with determinate and indeterminate growth habit.  Plants grown in large pots outdoor conditions were moved into sunlit plant growth chambers at initial flowering and five wide range of temperatures were imposed soon after flowering and continued to maturity. During the season, plant growth and development were estimated at frequent intervals. At maturity, plant-component dry weights and pod and seed numbers and weights were recorded. Significant temperature and cultivar differences were recorded among the many growth and developmental parameters measured.  The time from flowering and pod maturity declined with increase in temperature and quadratic function described best described the response in the both the cultivars. Cultivar AG 5332 took more time across the temperatures compared cultivar PR 5333 from flowering to seed maturity. The optima temperature for pod and seed number and weights were slightly lower than the optima temperature for total or vegetative biomass production. Also, optima temperatures for yield parameters were significantly different between the two cultivars. The AG 5332, an indeterminate cultivar, was more high temperature tolerant than the PR 5333, a determinate cultivar. The functional algorithms 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 for in-season management decisions for natural resource management and pesticide and irrigation input management decisions.