EFFECTS OF CALCIUM, BORON AND SORBITOL ON POLLINATION AND FRUIT SET IN MANGO CV. NAMDOKMAI

The effects of calcium, boron and sorbitol on pollen germination in vitro, pollen tube growth on stigma and fruit set in mango cv. Namdokmai were investigated. Both commercial and technical grades of calcium nitrate and boric acid were used in this study, while only purified sorbitol was employed. All chemicals were sprayed onto 5-cm long mango inflorescences. When 50% of the flowers had bloomed, pollen was collected for in vitro observations (Brewbaker and Kwack agar medium). Pollen tube growth on the stigma was examined by the aniline blue fluorescence method, every 6-hours for 48 hours from 6 hours after hand pollination. Fruit set was examined every 3 days for 45 days after full bloom. The results showed that the applied chemicals had no effect on pollen germination or pollen tube growth. The percentage of pollen germination in all treatments was 44.52% to 54.16%, and pollen tubes took 24 to 30 hours to reach the stigma ends. Although, calcium, boron and sorbitol did not influence pollen germination and tube growth, they did induce more fruit set in this mango cultivar. Therefore, it is anticipated that these chemicals may exert other effects on the fruitset.