Floral Biology of Common Buckwheat (Fagopyrum esculentum Moench)

Common buckwheat (Fagopyrum esculentum Moench) is widely cultivated but the floral biology of this auto-incompatible distylous species was poorly documented. This review, based on our recent results obtained with the cultivar ‘La Harpe’ and the literature, summarizes main aspects related to its reproduction: morphogenesis, flowering, nectar, pollination and flower functionality. The activity of the reproductive meristems is potentially endless but the morphogenesis is stopped by the abortion processes. When the plant has one unfolded true leaf, the morphogenesis of the reproductive structures occurs at many nodes and this developmental stage is highly sensitive to environmental stress. Hymenoptera (Apis mellifera L. and Bombus spp.) and Diptera (Syrphidae) are the main visitors. Honeybee appears to be an effective pollinator and the most numerous visitors in Western Europe. At the anthesis, ‘hexoses-dominant’ floral nectar is secreted by unicellular secretory hairs during all the light period even after pollination. Except for the morphology of the reproductive organs, both morphs differ only in the nectar production. Thrum flowers secrete more nectar than pin flowers. Pollinator abundance is an important parameter to secure the yield but even without pollen transfer limitation the seed set is low. Flower fate appears to be dependent on a mechanism internal to the raceme which controls the percentage of flowers able to set a seed. Infertile flowers with an undersized gynoecium and last abortions after fecundation are not frequent. In contrast, flowers with a normal sized gynoecium which do not set seed after compatible pollination are the main contribution to the low seed set. This female organ sterility seems to be the most yield limiting factor throughout the world. _____________________________________________________________________________________________________________