Nature of the Photoperiodic Responses of Buckwheat

1. Photoperiod had no effect on floral initiation in Tartary buckwheat, Fagopyrum tataricum Gaertn., but markedly influenced the regulation of vegetative growth, floral development, and fruiting. 2. Short photoperiods promoted floral development, fruiting, and lateral-shoot production, but depressed main-axis elongation. Long photoperiods favored main-axis growth and an increase in total plant weight but depressed lateral-shoot growth, floral development, and fruit production. 3. Although both floral and vegetative development are photoperiodically controlled, their control operates through separate mechanisms, as indicated by the results of experiments involving dark- or light-period interruption. Floral development is chiefly associated with a dark-dependent mechanism, which appears to be similar to the one controlling floral initiation of a typical short-day plant. Main-axis elongation is chiefly associated with a light-dependent mechanism.