Following the period of vegetative growth, which varies depending upon cultivar and environmental condition such as day length and temperature, the plant enters the reproductive stage, during which axillary buds develop into flower clusters of 2 to 35 flowers each. The node of the first flower is related to the development stage of the plant. Since nodes of the cotyledons, the primary leaves, and the first two or three trifoliolate leaves are usually vegetative, the first flower appear at nodes five or six and sometimes higher. Flowers form progressively toward the tip of the main stem and also toward the tip of the branches. Under favourable conditions, the period of bloom may extend from 3 to more than 5 weeks (Carlson and Lersten 1987). Several investigators have reported that a soybean plant produces many more flowers than can develop into pods. From 20 to 80% of the flowers are reported to abscise for various cultivars (Wiebold et al. 1981). Most cultivars with many flowers per node have a higher percentage of flower abscission than those with few flowers per node. Abscission can occur at the time of bud initiation, during the development of floral organs, at the time of fertilization, duringthe early embryo state, or at any stage of cotyledon development. Flower abscission occurs most often from 1 to 7 days after flowering, while pod abscission must be later than 7 days after flowering (Carlson and Lersten 1987). In general, the earliest and latest flowers produced tend to abscise most often.