Pollination biology in Bombax ceiba Linn.

A study of flower morphology, anthesis, pollen production, foraging nature of flower visitors, in vitro pollen germination and stigma receptivity of Bombax ceiba Linn. of the family Bombacaceae has been made. The flowers are large with numerous stamens which open in post middle night and continue up to the morning. Anther dehisced after flower opening. During daytime, different types of birds visit the flowers and subsequently help in pollen dispersal and pollination when stigmas remain receptive. Each flower produced 8,863,000 pollen grains which are of 3-colporate, with reticulate ornamentation and thick exine. In vitro pollen germination study indicated that best germination (97%) along with 2940 µm tube development, takes place in 20% sucrose combined with 500 µg/ml H3BO3 solution. Among different salts of Ca, Mg and K, only Ca(NO3)2·4H2O showed significant result with 54% germinating pollen along with 420 µm tube length in 50 µg/ml Ca(NO3)2·4H2O solution. Maximum stigma receptivity was noticed during the first day after anthesis with 61% in vivo germinating pollen captured with unicellular pointed papillae cells over receptive stigma surface. Atmospheric pollen frequency was found to be 5.17% in 10.00 h. No fruit setting was observed in netted and bagged flowers, which strongly indicates that some external agents are required for successful pollination.