The Comparative Study Of Reproductive Ecology In Bi-seasonal Flowering Periods Of Tamarix Ramosissima

The reproductive ecology research of special reproductive phenomenon in extreme desert ecosystem is the important way to find out the co-evolution problem between life history strategies and environmental factors.Tamarix ramosissima belongs to Tamaricaceae(Tamarix),which is a widespread species in Xinjiang desert ecosystem.It has flowering periods which happened in spring and summer.From the evolutionary ecological angel,the differentiation of reproductive traits under flowering periods is critial for understanding the reproductive adaptive tactic.This study intends to conduct the following research on the spring and summer flowering period of natural population through a series of wild investigation and laboratory analys is methods:(1)Bi-seasonal flowering phenology and reproductive features;(2)The floral syndrome and pollination characteristics;(3)The mating system characteristics;(4)The seed germination characteristics.We can not only further analysis the influence on reproductive ecological adaptability of phenology,but also can explore the adjust mechanism of floral traits on pollinat ion adaptation.Moreover,the ecological function differentiation of seeds from spring and summer flowering period will be discussed.Then,we can understand the ecological evolutionary significance of this special bi-seasonal traits.The new theory is expected on the "reproductive ecology of bi-seasonal species" research field.Besides,the results will provide theory evidence and case analysis for the understanding of multiple adaptive tactics of species under extreme desert environment.The main results of this study are as follows:1.The spring flowering period of T.ramosissima.was from late May to early June,exhibiting a “mass-flowering” pattern.The summer flowering period was from the middle June to early September,exhibiting an “extended-flowering” pattern;In spring and summer flowering periods,the flowering duration of the population,individuals,inflorescences and single flower were 14 d,10 d,3 d and 1 d,and 85 d,77 d,2 d and 1 d respectively;There were significant correlation among first flowering date,flowering duration,flower number and fruit number at inflorescences level of the summer flowering period;There was no significant differences in the flowering process and morphological structure between two flowering periods;The fruit rate and seed rate in spring flowering period are same higher than the summer flowering period,but there was no significant difference between two flowering periods.The survival conditions in ar id region of Gurbantunggut Desert is poor,bi-seasonal flowering and reproductive features of T.ramosissima raise the possibility of their reproductive success.2.There was no significant differences in the floral architecture and floral dynamics between two flowering periods of T.ramosissima;The visiting frequency showed double-climax in two flowering periods,and the visiting frequency in spring flowering period was significantly higher than that in summer.The effective pollinators in spring flowering period are Syritta pipiens,Eristalis arbustorum and Apis mellif era.While Apis mellif era is the only effective pollinator in summer flowering period.T.ramosissima is prone to cross pollination,and summer flowers tend to be self-pollinated,which is an environmental pressure to ensure that plants successfully complete reproductive choice in the most econmical and effective way.3.The stigma receptivity and pollen viability in spring flowering period is longer than that in summer flowering period.T.ramosissima exhibited a mixed mating system.There was no apomixis,self-compatible,and inclined to out-crossing.The spring flowering period was pollinators required,the summer flowering period relied mainly on selfing to realize reproductive success.4.The thousand seed weight,length and width of the seeds in spring flowering period were signif icantly higher than that in summer.There was no signif icant differences in percentage of germination and germination speed at four thermoperiods.With the decrease of temperature,the percentage of germination and germination speed of seeds were decreased in summer flowering period.The salt tolerance of seeds in spring flowering period was higher than that in summer.The percentage of germination and germination speed of seeds were decreased in two flowering periods with the increase of NaCl concentration.The percentage of recovery germination of seeds in two flowering periods were 0% treated by different concentration of NaCl solution.The drought tolerance of seeds in spring flowering period was higher than that in summer.The percentage of germination and germination speed of seeds were decreased in two flowering periods with the increase of PEG-6000 concentration.The percentage of recovery germination of seeds in two flowering periods were 0% treated by different concentration of PEG-6000 solution.The seed germination of T.ramosissima mainly depends on seeds in spring flowering period.The seed germination in summer flowering period is opportunistic strategy taken by the germination strategies to ensure its population in the harsh desert environment of continuously updated.