Studies On The Reproductive Biology Of Sonneratia Alba

Sonneratia alba is a mangrove plant in Sonneratia of Lythraceae.S.alba,a pioneer tree species in mangrove ecosystems,grows in the tropical and subtropical intertidal zones and has important ecological value and ecological service functions.Due to habitat destruction and human activities,the distribution range of mangrove communities has become increasingly narrow,and the number of populations and individuals has decreased year by year.S.alba,a pioneer tree species of mangroves,plays a very important role in mangrove afforestation,wind protection and soil solidification as well as water conservation.In this study,the natural population of S.alba in Qinglan Mangrove Nature Reserve in Wenchang City of Hainan Province was taken as the research object,and the principles and methods of reproductive biology were used to analyze and explore the flowering phenology,flower characteristics,breeding system,pollination process and seed germination of S.alba.The main conclusions wereas followed.(1)The flowering and fruiting period of S.alba wasall year round,and the population flowering florescence was from April to July and from October to November each year,and the single flower florescence was 2～4 days.According to the dynamic process of flowering,it could be divided into the initial flowering period,full blooming,end of flowering stage and flower shedding,it was corymb inflorescence,4.93±0.64 cm in diameter,and the flowers were white with petals.The pollen viability of S.alba was the highest at 3 days after flowering,reaching80.40±2.37%;the receptivity of the stigma lasted about 4 days,with the strongest on days 2and 3.(2)The outcrossing index(OCI)of S.alba,and the pollen-ovule ratio(P/O)was10060.18±709.28.Combined with the artificial control pollination experiment,it was judged that the breeding system of S.alba was mainly outcrossed,partially self-compatibility,and required pollinators.(3)The flower-visiting insects of S.alba were mainly Apis cerana and Oecophylla smaragdina.In the daily activity time range,A.cerana was mainly active in the morning,starting to visit flowers from 8:00,at 8:30～10:00 increasing rapidly,at 9:30 reaching the highest,and then gradually decreasing until the flower-visiting activities finish.On the contrary,ants visit flower throughout the time period,and the frequency was relatively stable.(4)The seed germination conditions of S.alba were optimal in 16 h/d light,30 °C and 0%salinity,and all indicators reached the maximum value.The S.alba had the strongest salt tolerance,and the adaptation range to salinity was the widest in Sonneratia,and germination could be in the range of 0～1.5% salinity.The action of exogenous hormones does not promote germination rate but can speed germination.In the natural state,the germination rate of S.alba was extremely low,and there were few seedlings and young trees in the forests which showed that the growth link from seedlings to young trees is relatively fragile.