Photoperiod sensing of leaf regulates pod setting in soybean (Glycine max (L.) Merr.)

Soybean is a short-day plant and is highly sensitive to photoperiod. How photoperiod regulates soybean flowering is well known, whereas how it regulates pod setting is poorly known. In this study, short-day treatment decreased the number of days from flowering to pod setting. The duration of short-day treatment and the number of days from flowering to pod setting were negatively correlated. Additionally, short-day treatment of flowers after flowering did not promote pod setting, whereas that of leaves significantly shortened the period from flowering to pod setting. Vascular tissue of the two stems of Y-shaped plants was not connected at the stem junction, and short-day treatment of leaves on one of the two stems did not promote pod setting on the other stem. It is likely that a signal produced in leaves under short-day condition moves to the nodes and promotes pod setting after flowering.