ABSTRACT
In animal-driven pollination, pollen and stigmas must match their locations on the visitor body, so as to accomplish pollination. In many Senna species, however, functional pollen-yielding anthers are positioned in a way to remain on the lower part of the bee body, whereas the long style positions the upper part of the bee. Our previous studies on Senna showed that when pollen-collecting bees vibrate the flowers, the released pollen jet ricochets against a deflector petal on its way to the bee back. Ricochet traits in Senna have likely evolved independently multiple times. They may indicate a key role of this mechanism in the adaptive radiation in the floral morphology in Senna. Moreover, species from many non-related angiosperm families, bearing poricidal or longitudinal dehiscing anthers, can also use a range of floral organs to rebound pollen similarly to deflector petals of Senna. Our observations may open new doors into the functioning of buzz-pollinated species. The ecological role(s), the evolutionary history, and the biophysics of ricochet-like mechanisms is still puzzling.
