Physiology of flowering and grain filling in faba bean

The development of flowers and then that of seeds are key processes in the formation of yield in faba bean (Vicia faba L.), as in other grain legumes. Winter faba bean generally has a quantitative vernalization requirement, allowing flowering to occur at a lower node than in unvernalized plants. Some germplasm is day-neutral, other germplasm is long-day with a critical daylength between 9.5 and 12 h. Progress toward flowering follows a conventional thermal-time model, with 830–1000 °C-d above 0 °C required for the onset of flowering and an optimum temperature of 22–23 °C. Flowers may abscise from the crop because of lack of pollination, because proximal flowers on the same raceme are fertilized, because of vegetative–reproductive competition for assimilate, or because of stresses such as drought.