Effect of Growth Regulators and Time on In vitro Pollen Germination in three Ornamental Tropical Tree Species

In vitro pollen germination of three tropical tree species, viz. Spathodea campanulata, Bauhinia purperia and B. racemosa was done to know the effect of growth regulators and time on pollen germination. Three concentrations, i.e. 100, 200 and 300 ppm of four growth hormones (IAA, IBA, GA(3) and Kinetin) and sucrose (5 and 10%) alone were used as germination medium. The results revealed that pollen germination under control condition is very low and oscillating between 4.6 +/- 1.2 and 17.8 +/- 3.2%. The growth hormones and sucrose was found effective inducing pollen germination. IAA and IBA were found effective for both species of Bauhinia whereas GA(3) and kinetin were found suitable for Spathodea campanulata. Maximum germination was recorded in the initial 24h of setting experiment, which further declined in 48h and was recorded very less and even 0.0% after 72 hours of treatment. There was significant (< 0.0001) effect of time, hormone and species on pollen germination. Sucrose has shown good response (43 to 64%) in all selected tropical tree species. All the three tree species are cross pollinated, which depend on the variety services of pollinators. Low % in vitro pollen germination in control condition in Spathoda campanulata and Bauhinia purpurea reflects that both species are prone to pollination and fertilization failure if appropriate pollinators and receptive stigmas are unavailable to them early after anther dehiscence.