Morphological Response of Soybeans as Governed by Photoperiod, Temperature, and Age at Treatment

The morphological response of soybeans to photoperiod and temperature was analyzed. The plants were exposed to seven combinations of short- and long-day photoperiods at two stages of development and grown under four day/night temperature regimes. Development of axillary branches at lower nodes of the main stem varied with temperature and with stage of development at induction. The number of potential sites for floral initiation was related to the total number of (1) main stem nodes, (2) axillary branches, and (3) nodes on the axillary branches. Development of floral primordia was influenced by the interaction between photoperiod and temperature. Two- to threefold differences between the mean flower:node and pod:node ratios were obtained.