Floral Biology of Aquilaria crassna Pierre ex Lecomte

Abstract

Flowers of Aquilaria crassna Pierre ex Lecomte generally start early March to May. Flower buds develop to maturity of inflorescences within three weeks and non-pollinated flowers fall within five days. The flower is of perfect flower, consisting of calyx-tube, collora-tube, androecium and gynoecium. The pollen shape is of sphaerical with small size (20-25 µm in diameter) with gemmate exine. The papillae stigma is of capitate with 0.7 mm in length. The flowers start blooming in evening during 16.30 – 18.30 hrs, the peak of blooming at 18.00 hrs. The flowers are weakly protandrous, which the anthers dehisce prior to pistil receptivity. Flowers have ten anthers, each anther containing approximately 1,937 pollen grains. A high P/O ratio (9685.5) indicates that A. crassna is highly outcrossed and is classified as obligate xenogamy. In other words, the species likely requires cross-pollination for natural regeneration. Opened pollination produces low initial fruit setting (2.23%) and reproductive success appears low (0.05). The phenomena where a low proportion of flowers was developed into fruit despite most ovules having developed into mature seeds indicates that the rate of fruit abortion is higher than for seed. 

Keywords:  Aquilaria crassna Pierre ex Lecomte, Flower development,  P/O ratio,   Pollination, Reproductive success