Effect of pollination on flower abortion, fruit set and fruit production in four mangroves species

Abstract

The study was conducted in Nyeke and Michamvi mangrove forests in the southern region of Unguja Island in Zanzibar. This study was designed to examine the effect of pollination on buds, flowers, fruit sets and fruits of four mangrove species namely Rhizophora mucronata, Bruguiera gymnorhiza, Ceriops tagal and Avicennia marina. The selected mangrove branches were free from pest and diseases and have been selected randomly, and observations were carried out twice a week in the period of nine months. A total of 80 trees (20 trees per specie) were randomly selected. The height of the selected trees was approximately 3.5m. Four treatments were established on flowers of the selected branches. The treatments were: open pollination (control), open plus hand cross pollination (pollen supplement), closed self-pollination (bagged), and closed plus hand cross pollination (bagged supplement). The results showed that in all four mangrove species there were significant differences in the number of buds, flowers, fruit set, visitors, visits and fruits. High number of flowers aborted was reported in bagged treatments in both sites compared to other species. But the number of fruits produced was higher in bagged supplement treatments in both sites. The increases of the number of flowers produced also reflecting to the number of buds produced. Increase number of flowers concurrently increase on the number of fruit set in all species, although A marina showed a weak relationship. The study concluded that the increase on the number of mangroves fruits not only depends on the number of fruit set and other reproduction variables, but also there was other abiotic and biotic factors that require intensive investigation.