The Reproductive Characteristics And Spatial Pattern Of Caryopteris Mongholica Bunge With Different Colors

Reproduction is a fundamental issue that affects the formation,continuation and evolution of plant populations and is the basis for the evolution and development of biological communities and ecosystems.Caryopteris mongholica Bunge is the dominant Plant Resource in arid and semi-arid regions of northern China especially typical grassland areas.It is of great importance to study on the breeding characteristics and spatial distribution pattern of Caryopteris mongholica Bunge for the reasonable development and utilization of this ecological tree species in the ecological fragile zone of arid and semi-arid areas in China.In this paper,two species of blue-violet and light pink Caryopteris mongholica Bunge distributed in northern mountains of Lanzhou city were selected as the research object.Through the analysis of the flower characteristics,pollination insects,volatile compounds,seed setting,seed germination and spatial pattern,the author attempts to understand the reproductive characteristics of Caryopteris mongholica Bunge and its adaptability to the environment and to explore the reasons of the less population of light pink Caryopteris mongholica Bunge so as to provide the basis for plant resource utilization,biodiversity conservation and ecological construction in arid semi-arid and desert areas.The main results are as follows:1.The florescence of blue-violet and light pink Caryopteris mongholica Bunge distributed in northern mountains of Lanzhou city is from July to October.The mean blooming period of blue-violet Caryopteris mongholica Bunge is 79 days,and the flowering period of one flower is 4.1 days.The mean blooming period of light pink Caryopteris mongholica Bunge is 73 days,and the flowering period of one flower is 4.45 days.Initial blooming time of light pink Caryopteris mongholica Bunge is late.Flowering processes are in similar model of “Mass-flowering pattern” that is good for the attraction of its flowers to pollinators.Light pink Caryopteris mongholica Bunge were smaller in size and the colors were not as bright as those of blue-violet Caryopteris mongholica Bunge,but under the same flowering time,the stigma height of them was higher and easier to touch pollination insects,and the amount of nectar was more,which provided more flower visiting reward for flower-visiting insects.Despite all this,Apis cerana Fabricius of Apidae is the main insect pollinator of Caryopteris mongholica Bunge.blue-violet Caryopteris mongholica Bunge insect pollinators have a relatively high flower visiting frequency.There are significant difference between the insects flower visiting frequency of 2 different colors of Caryopteris mongholica Bunge.The breeding system of 2 different colors of Caryopteris mongholica Bunge are facultative hybridization.2.The main floral volatile components of blue-violet Caryopteris mongholica Bunge were ?-pinene,3-carene,6,6-dimethyl-(1R)-bicyclo[3.1.1]heptan-2-one and ?-terpinene;while in blue-violet Caryopteris mongholica Bunge,the main foliage volatile components were ?-terpinene,(E)-2-octene,1,2-dimethyl-cyclooctene,?-farnesene,ocymene,doconexent and 3-ethyl-5-methyl-s-triazolo[4,3-a] pyridine.The main floral volatile components of light pink Caryopteris mongholica Bunge were 2-amino-2-oxoacetic acid-N-[3,4-dimethylphenyl]-ethyl ester,2-propenoic acid,3-(4-methoxyphenyl)-2-ethylhexyl ester,o-cymene and D-limonene,(1R)-2,6,6-trimethylbicyclo[3.1.1]hept-2-ene;while in light pink Caryopteris mongholica Bunge,the main foliage volatile components were(E)-2-octene,2-methyl cyclosarin,methoxyacetic acid-tridecyl ester,isopropyl myristate,tetradecane,o-cymene and 2-(trimethylsilyl)-mercaptoacetic acid.The main type of floral and foliage volatile components of blue-violet Caryopteris mongholica Bunge is terpenes that is more similar to the volatile components of other plants of Caryopteris.The main type of floral and foliage volatile components of light pink Caryopteris mongholica Bunge is esters.There are significant differences in the components of volatile substances in 2 different colors of Caryopteris mongholica Bunge.This difference is likely to be one of the factors that affect the frequency that pollinators pollinate 2 different colors of Caryopteris mongholica Bunge.3.The seed set of 2 different colors of Caryopteris mongholica Bunge was about 44-45% and 54-67% in 2016 and 2017.However,the seed set rates of different populations exhibited the same regulation on branches,manifested as the middle part > top part > basal part.Compared with light pink Caryopteris mongholica Bunge,the seeds of blue-violet one were bigger and heavier,and the germination rate,germination vigor and quality were higher than those of light pink one.Besides,the difference of seed setting rate was probably related to the poor stigma pollination of light pink Caryopteris mongholica Bunge,which was caused by the poor insect pollinator.One of the reasons for the small number of light pink Caryopteris mongholica Bunge was that the seed setting rate and germination rate of those were lower than those of blueviolet one.4.The 2 different colors of Caryopteris mongholica Bunge has the main spatial distribution pattern of the aggregation distribution in plot.The blue-violet and light pink Caryopteris mongholica Bunge gradually become positively correlated with the increasing spatial scale.Spatial pattern of aggregation and distribution was beneficial to the natural resource competition of Caryopteris mongholica Bunge population with other plant populations in this area,which made its flowers more attractive to pollination insects and improved its pollination efficiency.Futher more,Caryopteris mongholica Bunge population obtained more natural resources,and adapted to the harsh natural environment,such as drought and fewer insects in Beishan area of Anning District,Lanzhou as well,lastly increase the probability of successful reproduction.In conclusion,in order to cope with the environmental stress caused by the low number of pollinators and environmental drought and other habitats,Caryopteris mongholica Bunge was adapted to the harsh natural environment of the region through a more concentrated flowering pattern,brighter flower colors,faster seed germination,and a spatial distribution pattern of agglomeration,which ensured the success of Caryopteris mongholica Bunge breeding.Compared with the blue-violet Caryopteris mongholica Bunge,light pink Caryopteris mongholica Bunge are still in a disadvantaged population and are less in number.