Study On The Breeding System Of Osmanthus Serrulatus Seed Physiological And Ecological Characteristics

In this paper,the object of study is Osmanthus serrulatus Rehd,also named Baoxing sweet-scented osmanthus,it is a kind of endemic plant in our country and its type locality is Baoxing County.It is recorded in the Flora of China that O.serrulatus is distributed in Sichuan,Guangxi and Fujian,while in recent years,it can be only found in Xiling Snow Mountain,Mount Emei,Mount Dongla and other places of Sichuan province.The species community of O.serrulatus intensively distributed in 1800²300m altitude of Dongla Valley is the largest natural population found in the world so far.O.serrulatus is one of the Osmanthus categories flowering in spring seldom,the flower is big,fragrant and very beautiful.In the early 20th century,the seed of such plant was collected by Wilson,etc.Since then,the plant has been cultivated in Royal Botanic Gardens,Hiller Arboretum and other places,and now,it has grown into big tree.And furthermore,it has been applied in the gardens and parks of Britain,Europe,America and other countries,while,such kind of plant has been not developed and utilized in China.In recent years,due to the damage of ecological environment,the distribution of O.serrulatus has increasingly reduced and the number of individuals has been rare day by day,and what‘s worse,the plant has been in danger of extinction.In this study,through the comparative studies on the community structure,spatial distribution pattern,environment interpretation,seed ultrastructure,seed germination characteristics,habitat heterogeneity,flowering phenology,floral syndrome,breeding system,pollen ecological characteristics and other aspects of the endemic plant from China,namely,the O.serrulatus population,the bionomic strategies of O.serrulatus.In the aspects of population ecology,reproductive ecology and physiological ecology as well as its increasingly scarce reasons are discussed.The results show that:1.The results show that there are 235 species belonging to 144 genera in 78 families of vascular plants in the community.Particularly,O.serrulatus has the highest importance value in arbor and shrub layers,occupies absolute advantage.The comprehensive analysis shows the O.serrulatus community is the alpine coppice community mainly composing by shrubs and herbs,and is obviously effected by temperate components,and has certain relationship with tropical components,which showing transitivity and complexity of floristic composition.The species diversity is related to the species number and distribution uniformity.O.serrulatus is the constructive species in the community with a concentrated distribution and obvious advantages,positioning at the transition stage from relatively stable middle succession to fading population.In this study,the classification and ordination of the O.serrulatus community in western Sichuan mountain regions was performed in order to lay a foundation for further analysis of the biodiversity pattern and maintenance mechanism of the fragmented and crushed habitat of the O.serrulatus community.24 community plots were divided into 12 coenotypes by TWINSPAN,which revealed the community successional trend in space.The DCCA ordination results verified the rationality of the TWINSPAN classification,and indicated that the organic and humus content were mainly environmental factors which influenced the O.serrulatus plant community type and spatial distribution.Geostatistics method in combination with GIS was employed in this research to study the spatial distribution characteristics of soil nutrients for O.serrulatus community and figure out the coordinated relation between O.serrulatus community and soil nutrients with Dongla Mountain in Baoxing County of Sichuan Province as the study area,aiming at protecting the O.serrulatus population which is declining due to habitat fragmentation.The distribution of O.serrulatus community in Dongla Mountain is significantly correlated with the content of organic matter,nitrogen,phosphorus and potassium in community soil and the nitrogen,phosphorus and potassium determine the reproductive pattern of O.serrulatus community.As part of the whole O.serrulatus ecosystem,soil achieves the balance of matter and energy in the ecosystem,leading to the formation of?isolated island?of small ecosystem by O.serrulatus among the geographical isolation suitable for their growth.2.Seed coat development of O.serrulatus and the possible role of the mature seed coat in seed dormancy were studied by transmission electron microscopy?TEM?and scanning electron microscopy?SEM?.The results show that:1 SEM found that luteolin short silk seed seed coat internal surfaces and contain wax,along with Seeds continues to mature,the wax is not short accumulated to form a layer of wax,to improve the poor environment of the outside world resilience,but also an impediment to the seeds absorb water.During seed development short wire Reseda,progressively differentiate into palisade parenchyma cells cell,mature seed coat seeds Osmanthus short wire by the stratum corneum,palisade cell layer,three-layer structure composed of thin-walled cell layers.The stratum corneum and the fence layer affect the penetration and permeability of the seed coat,which is one of the factors contributing to the dormancy of the seed.The seed germination characteristics of O.serrulatus,an aromatic plant that endemic in China,were studied in this paper.The results showed that the dormancy of O.serrulatus was comprehensive and with the physiological after-ripping phenomenon;the peels hindered seeds water absorption;variable temperature stratification could effectively break seed dormancy and accelerate seed germination.High performance liquid chromatography was used to measure the contents of four endogenous hormones?ZT,GA₃,IAA and ABA?in O.serrulatus seeds during variable temperature stratification.The regular changes of ZT,GA₃,IAA and ABA and their proportions in O.serrulatus seeds during variable temperature stratification were further analyzed,providing a foundation for understanding the breaking of seed dormancy in O.serrulatus.The results showed ideal chromatographic separation of hormones in the seeds.The standard recovery rates of ZT,GA₃,IAA and ABA were 98.70%,98.56%,99.03%and 99.00%,respectively,and all relative standard deviations were<1.44%.Therefore,this method could rapidly and accurately separate and measure the endogenous hormones in O.serrulatus seeds.The GA₃ content showed an initial decrease followed by increase,while the IAA content was not obviously related to breaking dormancy.3.To reveal the pollen competition in plants of different genders and its competitive mechanism via the exploration of the direction and scope of pollen dispersal of O.serrulatus;and to investigate the relationship correlation between plaque size and the adaptability of free pollination progeny,so as to provide a theoretical and technological foundation for further study of floral evolution,wild population genetic and conservation strategies of O.serrulatus.O.serrulatus,a kind of androdioecious plant,was studied in this paper.A statistical investigation of the sex of individuals in 24 samples of different O.serrulatus populations collected from Donglashan Valley,Baoxing County,Sichuan Province was carried out.An observation of pistil morphology,number of pollen grains,and external features of unisexual male individuals and hermaphrodites of O.serrulatus was made then a comparison was conducted;10 pairs of polymorphic SSR primers were introduced to analyze 271 candidate male parents and 494children plants of 24 population samples.1)For O.serrulatus in Donglashan Valley,the ratio of male individuals and hermaphrodites is 1:1.The pistils of the flowers of hermaphrodites develop soundly,while the flowers of unisexual males show a reduced pistil.2)Calculation at 80%confidence level was performed for 376 children?76%?to identify the sole male parent.Of all the children whose male parents had been identified,respectively 213 and 163 children were derived from male parents and bisexual parents.3)The average effective dispersion radius for the pollens of the 24 samples of different O.serrulatus populations in Donglashan Valley was46.35±25.62m.The mating distance of mother plants showed approximate normal distribution,further indicating the outcrossing of the plant.Plant density,altitude,wind direction and other factors can affect the mating pattern of O.serrulatus.Experiments showed that natural populations of O.serrulatus are functionally androdioecious and self-compatible;and the reproduction system may be a transitional type evoluting from hermaphrodite to diclinous plant.4.We have investigated the impacts of birds on the seeds of O.serrulatus for three consecutive years from 2015 to 2017.Mature O.serrulatus fruits complete their regeneration and succession of population through the spreading seeds digested from fruit-eating birds.A total of10 species of birds were found feeding on the seeds of O.serrulatus and formed a seed-transmission relation with 6 kinds of birds.The home range and distance of propagation were very long for the red-billed blue magpie,but the frequency of feeding was low;black bulbul and pycnonotus sinensis were the main seed spreaders because of their high frequency of visiting and feeding.The analysis of the distance between the first resting point and the mother tree after feeding and the potential distribution of the seed showed that the birds can spread the seeds of O.serrulatus at a long distance,and the propagation and population renewal can be achieved with the help of the birds.