Time of Flower Opening and Seed Mass in Soybean1

Abstract

AbstractSeeds from an individual soybean [Glycine max (L.) Merrill] plant exhibit a range in seed mass, the cause of which is not well understood. This research was conducted to investigate the relationship between the time of flower opening and seed mass. Five soybean cultivars (Cumberland, Harper, DeSoto, Douglas, and Essex) were grown in the field using conventional cultural practices in 1984 and 1985. Fully open flowers were marked with acrylic paint at growth stages R1 to R4.5. Fruits from marked flowers were harvested at maturity and seed dry mass determined. The range in seed mass was estimated using round‐hole screens. The rate of seed development was monitored by determining when seeds reached 3 mm in length and when the pod turned yellow. Mean mass of seeds from flowers opening at R4 or R4.5 was less than mass of seeds from earlier flowers, and this was associated with a shorter seed filling period. Seed mass was not consistently related to time of flowering for flowers opening at R1 to R3. There was a range in seed mass within a time of flower opening, and most of this variation was associated with variation in seed growth rate. Applying fruit removal treatments when pods from the marked flowers reached maximum size indicated that the maximum potential mass of seeds from late flowers was much larger than the normal mass. The data indicate that the time of flowering accounts for only a portion of the variation in seed mass of a soybean plant.