Studies On Reproductive Biology Of Lagerstroemia Speciosa

In this paper,reproductive biology of Lagerstroemia speciosa in Guangxi University were investigated for the first time,including flowering phenology,flower morphology,single flower open dynamics,breeding system,pollination mechanism and male and female gametophyte development.In order to enrich the research of reproductive biology of Lagerstroemia speciosa,and lay a scientific theoretical foundation for the future research on hybrid breeding and tree species improvement.Main conclusions are presented as follows.(1)The flowering span of the population of Lagerstroemia speciosa was 94d from the middle May to late August.The flowering duration of inflorescences was 31.17± 3.40d,the average flowering number was 80.87 ±35.42,and the flowering amplitude is in the form of single peak.Flowering duration of single flower was 4.67±1.52d.The flowering period of individual plants was 67.9±19.28d,the flowering pattern was 'substantial and concentrated flowering',the synchrony index was 0.79,the relative flowering intensity frequency distribution is concentrated in 40%?60%and the skewness was 0.598.In sunny days,the overwhelming majority flowers concentrated in full bloom before 8:00AM.In cloudy or rainy days,a part of flowers postponed flowering or buds do not bloom after cracking.(2)The strongest pollen viability of Lagerstroemia speciosa was 73.67%and the pollen life was only 1d.The receptivity of stigma was 1?3 days before blossoming to 4 days after blossoming.Lagerstroemia speciosa did not exist no fused reproductive condition,with self-compatibility,belonging to the mixed and self-intersection mating system.and need to use insects for pollination.(3)The flower of Lagerstroemia speciosa was bright purple,no fragrance,lots of pollen and relied on pollen as a reward to attract pollination insects.A total number of 17 species of insects were recognized as the flower visitors.There were 15 species of main pollinators,which the most important pollination insects were Bombus festivus and Apis cerana cerana.The highest visiting frequency in a day was observe at 8:00?10:00 in sunny days and the flowers no longer appear to visit insects after 12:00.(4)The anthers of Lagerstroemia speciosa has 4 pollensacs.Anther wall consists of four layers of cells,including epidermis,endothecium,medial and glandular tapetum.The development of anther wall follows the dicotyledonous type.The cytoplasmic division of microspore mother cell meiosis was the simultaneous type.The tetrad is formed after the microspore meiosis.The vast majority of tetrads are tetrahedron type,and the few belong to the cross type.Mature pollen grains were 2-cell type,with 3-bore sulcus type.(5)Lagerstroemia speciosa was multiple carpels pistil,about 6?7 carpels.Each ovary has 6?7 locules,bearing a number of anatropous ovules with double layers integument and crassinucellate ovule in the axile placenta.The megaspore meiosis produces four linear megaspores.Only chalazal megaspore eventually developed into 7-celled or 8-nucleate embryo sac,and belongs to polygonum type.