Durian floral differentiation and flowering habit

Flower bud differentiation and the flowering habit of durian (Durio zibethinus Murray) 'Mon Thong' from budbreak to anthesis were investigated at the Chantaburi Horticultural Research Center in Thailand. Clusters of flower buds appeared at the end of November on primary or secondary scaffold branches near where a flower cluster occurred the previous year. Anatomical observations revealed that the development of floral organs was acropetal; the five fused epicalyx forming a large, elongated envelope enclosing the sepals, petals, stamen and fused multi-carpellate pistil. Floral organ development was completed in early January. The mature flower bud more than doubled in size one day before anthesis, with anthesis starting around 1600 HR and ending approximately equal to 1900 HR. The anthers did not dehisce until the completion of flowering. This change induced heterostyly in this cultivar, which promoted out-crossing by reducing the possibility of self-pollination. Aromatic nectar that attracted insects to the flower was secreted during anthesis. This is the first report to have clarified the overall flowering process in durian and provides the basic information for elucidating reproductive biology of durian in future research.