Flowering phenology and germination ability of pollens for Acacia mangium and A. auriculiformis

A four-year investigation was conducted on the flowering phenology and germination ability of pollens from A. mangium and A. auriculiformis ramets to determine whether the flowering phenology and germination ability of pollens differed among clones or seed sources. The number of A. mangium and A. auriculiformis clones used was 19 and 23, collected from 17 and 8 seed sources, respectively. The flowering of each ramet was visually observed every three or four days for three seasons, with one season being from April to the following March, and the germination ability of pollens collected from the flowers was investigated at 1 day, 6 months, and 12 months after being stored at -18 degrees C. The mean percentage of flowering per clone which was calculated by dividing the number of flowering ramets by the number of ramets used was low on A. mangium for each season, whereas it was more than 60% on A. auriculiformis for each season, with no significant variations among the seasons. The flowering initiation and flowering period also showed non-significant variations or differences among the seasons and among most of the clones within the seed sources. On the other hand, the percentage of flowering per clone, the flowering initiation, and the flowering period on A. auriculiformis showed significant variations and differences among the seed sources although those were similar on some seed sources. On both tree species, the germination rate of pollens per clone showed significant variations among clones, regardless of the seasons and number of days stored, and also among clones within seed sources for about half the cases. These results suggest that the flowering phenology is in some degree determined by a genetic factor such as the seed source, whereas the germination ability of pollens is mainly determined by a genetic factor in each clone.