Effect of Variation in Temperature During Photoperiodic Induction Upon Initiation of Flower Primordia in Biloxi Soybean

Biloxi soybeans were grown in the greenhouse for four to five weeks and transferred to a series of control rooms where various combinations of temperature during the photoperiod and the dark period were applied for five days. Photoperiods of both 8 and 16 hours were used. 2. The effect of these various temperatures on the initiation of flower primordia has been determined. 3. Initiation of flower primordia was influenced to a much greater extent by variation in temperature during the dark period than by variation during the photoperiod. 4. When the temperature during the photoperiod was constant, a 55⚬ temperature during the dark period limited the amount of initiation that occurred. At 65⚬ initiation was much more extensive. This rise of 10⚬ in temperature during the dark period produced a greater difference in initiation than any other temperature variation of the same amount. 5. Variation in temperature resulted in the formation of different numbers of nodes. These differences, however, were not great enough to account for the differences in floral initiation. 6. Other measurements, such as fresh and dry weights, stem lengths, and leaf areas, were made. All were influenced by the different temperature treatments. 7. The carbohydrate and nitrogen content of the plants was also influenced greatly by the different temperature treatments. As the temperature during the dark period was increased the carbohydrates decreased and the nitrogen fractions increased. These changes in carbohydrate and nitrogen metabolism could not be correlated with the morphological responses. 8. None of the temperature combinations used in these experiments brought about the initiation of flower primordia when photoperiods of 16 hours were used.