Biannual pollen production in Lagerstroemia speciosa (L.) Pers. (Lythraceae)

This study aims to analyse the flowering phenology and variation in total pollen production per tree in the natural populations of Lagerstroemia speciosa during seven successive years, i.e. 2006-2012. The production of flowers and pollen grains per tree varied intermittently every two years. In the mass production years, pollen production ranged between 9.48 x 10(8) and 9.8 x 10(8), whereas in poor production years, the values were between 4.6 x 10(7) and 5.1 x 10(7) pollen per tree. The study also revealed that the reproductive phenophases of L. speciosa were highly variable in the individuals of the population during different years, henceforth the flowering period endured for three months. The maximum anthesis in this species occurred in the morning between 05:00 and 10:00. On an average, a flower took 2.5 to 3hours for complete opening. Anther dehiscence occurred half an hour after anthesis. Bees of the genera Apis and Xylocopa were the main pollinators in L. speciosa. The visitation rates of pollinators were also different among individuals of the population, which varied from 0.62 to 2.82 visits/flower/hour with an average visitation of 1.68 +/- 0.94 visits/flower/hour.