“Push and Pull”: Biomechanics of the Pollination Apparatus of Oncidium spp.

Comprising ca. 28,000, species the Orchidaceae constitute one of most species-rich plant families. Orchids differ from other monocotyledons i.a., in formation so-called pollinaria, which are entities consisting pollen grains aggregated into compact pollinia and accessory structures, a viscidium mostly also pollinium stalk. The releases an adhesive material that attaches pollinarium to pollinator. Pollinaria part complex pollination apparatus enables orchids colonize niches only few individuals respective pollinator occur infrequently. Because removed flower at once, development mechanical barrier ensuring suitable pollinators able access flowers more importantly remove important selective traits. In this paper we describe functional morphology two orchid species, Oncidium wentworthianum O. otogaya , by experimentally mimicking process. Furthermore, analyzed resistance means force measurements showed it probably constitutes hierarchical two-stage barrier. first stage consists presence anther cap not protects pollinia, but serves prevent premature removal young unripe pollinaria flower. As soon as ripe, sheds second takes effect, severable bond between rostellum. This can be overcome potential pollinator, applying load least 10.8 mN ( ) or 12.6 ), respectively, on same time disengages its anchorage. produced creates sufficient contact Potential pollinators, such Centris spp. Trigona bees, should well exert forces pushing their head/forebody flowers. Thus, whether is detach depends both how forcefully push strongly pull apparatus.