Pollen Viability and Pollen-tube Growth Following Controlled Pollination and their Relation to Low Fruit Production in Teak (Tectona grandisLinn. f.)

Pollen released at 1100 h has the highest viability (92.2%) but is no longer viable 3 d (84 h) after anthesis. In vitro pollen-tube growth is fast (140 μm h −1 ) and increases significantly within the first 8 h. In vivo pollen tubes also grow quickly and reach the base of the style within 2 h after pollination and enter the micropyle 8 h after pollination. There is no significant difference between self- and cross-pollination in either the rate and the number of pollen tubes in the pistil and the number of ovules penetrated by a pollen tube. Teak has late-acting gametophytic self-incompatibility; the majority of pollen tubes grow through the style but some do not continue to grow from the style towards the embryo sacs. Pollen-tube abnormalities include swollen, reversed, forked and tapered tips and irregular and spiralling tubes. These are most prevalent in self-pollination (20.4%). The index of self-incompatibility of 0.17 and low fruit set following self-pollination (2.49%) indicates that teak is mostly self-incompatible. Drastic fruit abortion occurs within the first week following controlled pollination. Within 14 d, fruit size and fruit set from cross-pollination is generally much greater than from self-pollination.