The effect of bee visitors and style movement on seed set of Nigella sativa L. (Ranunculaceae) grown under semiarid conditions

Pollination systems of Nigella sativa were studied during the 2009 growing season under semiarid Mediterranean climate. Nigella flowers were subjected to different pollination conditions, open versus covered and hand-self versus cross pollination and emasculated open pollinated flowers. Also the role of style movements in pollination of Nigella flowers was evaluated. The results indicate that Nigella sativa is completely self compatible; the main visitors were honeybees and the flowers were unattractive to other wild bees under study conditions. The results also show that Nigella sativa is not fully pollinated in the absence of insect pollinators; wind plays little or no role in its pollination processes. The mechanism of style movement and its role in flower pollination are discussed. Under arid conditions the bees synchronized their flying activities outside the hives with the availability of nectar and pollen grains in flowers in the morning at the time of style bending near the stamens to ensure effective contact with the visitors.