Floral biology of Malaysian ‘Tekam Yellow’ jackfruit

Floral biology has important practical implications given that flower characteristics could affect the shape and size of fruit which leads to yield production. Consequently, information on the floral biology of ‘Tekam Yellow’ jackfruit is essential as it is a local breed of Malaysia with commercial importance for export. Hence, a study was undertaken on the floral biology of ‘Tekam Yellow’ jackfruit. A total of six growth stages were observed in male and female inflorescence spikes of jackfruit, with the aid of camera, scanning electron and fluorescence microscopes. Male spike took 38.5±10.5 days from stipule covering state until it fell off as black mass. Initially, stomata interspersed among the trichomes on perianth surface of growth stage 1 male inflorescence. At growth stage 2, the perianth tip of male flower split and exposing anther. By growth stage 4, odour was emitted from male spike while anther dehisced with splitting of pollen sac and thus released pollen grains. When male inflorescence entered growth stage 5, more than 50% of male spike surface was covered with yellow functional anthers. Eventually, fungus attacked the male spike and it fell off as black mass. In order to achieve growth stage 6, female spike took 42.5±10.5 days from stipule covering stage of 1. By growth stage 6, more than 75% of stigmas have been successfully fertilized. Stigma of female spike protruded gradually from split perianth. Initially, the shape of stigma was erected straight. When female spike entered growth stage 4, some of the stigma showed spathulate or ligulate shape with slight curve indicating it has entered receptive state. By growth stage 5, 50% of the stigma was in receptive state and it decreased to 25% when the spike grew to stage 6. The successfully fertilized female spike developed into syncarp (multiple fruit) at the end of growth stage 6. The receptivity of a single stigma lasted about 5 to 7 days, followed by bending and withering, indicating the stigma has a window of 5 to 7 days before senescence.