| Acacia mangium Willd and A. auriculiformis Cunn. ExBenth are the main introduced tree species for plantation in southern China. A. mangium grows fast, but the tree has the weakness of bad stem-form, wide canopy and weak cold tolerance. A. auriculiformis grows relatively slow, but the tree has better stem-form, narrower canopy and better cold tolerance. Crossbreeding of the two species is the effective way to breed new varieties of fast growing, better stem-form, narrower canopy and cold resistance. In this paper, the characteristic of flowing phenology and pollen biology of Acacia mangium Willd, A. auriculiformis Cunn. ExBenth and A. mangium WilldxA auriculiformis Cunn. ExBenth were studied, the acacia pollen storage, artificial pollination and hybridization techniques were also explored. The research results provide reference for acacia cross breeding. The main results are as follows:1. Observation of the flowing showed that the florescence of A. mangium was from August to November, and A. auriculiformis from June to November. The flowering phases were separated, with a flowering period of 3?5d and 6?15d interval cycling alternating pattern. The florets of A. mangium, A. auriculiformis and A. mangiumxA. auriculiformis opened at night, and almost stopped in the daybreak. The pollen maturation time was related to inflorescence insertion position, inflorescences at the southeast began matured at 6:00 a.m. firstly, and most of the inflorescences matured from 8:00?9:00 a.m..2. Culture in vitro of pollen germination indicated that the best nutrient solution formula was:15% sucrose+150 mg.L"1 Boric acid+1.Ommol.L-1 calcium chloride. Tests of the rapid determination techniques of the acacia pollen vitality, such as TTC dyeing, inorganic acid dyeing, I2-KI dyeing, Benzdine dyeing and FDA fluorescence detection dyeing method, indicated that FDA fluorescence detection method was the optimum method.3. The FDA fluorescence detection showed that the fresh pollen had the highest vitality, and the vitality declined remarkably as the standing time extended. The fresh pollen with a vitality of 97%?100% lost the vitality after 48h standing time in the room with the temperature of 30? at noon. FDA fluorescence detection of the acacia pollen dried at the temperature of 35? and 40? after 2-6h showed that the fluorescence disappeared quickly, so acacia pollen could not be stored after a drying process. The moisturizing fresh-keeping inflorescence refrigerated at 5? for 12d kept the pollen vitality over 95%, but the vitality decreased linearly to zero in 13-15d, this result showed that pollens of A. mangium, A. auriculiformis and A. mangium×A. auriculiformis could be stored by this way for the artificial hybrid pollination, while their flowering phases staggered in the same florescence. The fresh inflorescence without dehydration process refrigerated in liquid nitrogen at -18? or -80?, lost the vitality in 40d.4. Taking heavy pruning at flower-bud differentiation stage and spraying 0.1% boric acid +0.2% monopotassium phosphate continuously during flowering phases could effectively promote flowering and increase the rate of natural podding.5. Statistics of the A. mangium self-fruited pods showed ISI (Index of Self-Incompatibility)?0.12<0.2, indicating that A. mangium was self-incompatibility. The acacia podding rate of artificial pollination by bagging and thinning flowers without emasculation was significantly higher than with emasculation. So the effective way of artificial pollination was bagging and thinning flowers without emasculation, pollinating at 6:00?7:30 a.m. with the fresh pollen collected on that day or from moisturizing fresh-keeping inflorescence.6. The each other as female or male parents cross combinations of A. mangium, A. auriculiformis and A. mangium×A. auriculiformis, were designed for hybrid pollinations. Among the combinations pollinated on the same day, the pod lengths of the different female trees with the same male parent tree were significantly different, the same female tree with the different male parent trees had not significant differences, indicating that the pod lengths were related to female parent trees. The number of pods in a single inflorescence, both of the different combinations pollinated at the same time and the same combination pollinated at different time, varied greatly, indicating that the pod-bearing was greatly influenced by the pollination time and the inflorescence individual differences.7. A. mangium artificial pollination in early October produced higher podding rate, but got lower seed setting rate, the same as the natural pollination in the same term. Three years consecutive observation showed that the seed setting rate by the natural pollination during flowering phases before September was higher than the later, indicating that low temperature was adverse to the acacia fertilization. So acacia artificial pollination should be carried out during July to August by promoting flowering earlier. |
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