The Preliminary Study Of Reproductive Biology In Lespedeza Davurica

Lespedeza daurica is a perennial herbage of Leguminosae.It displays excellent characteristics such as cold tolerance,drought tolerance and barren tolerance.It is widely distributed and has high nutritional and medicinal value and ecological effects.At present,the research on L.davurica mainly focuses on biological characteristics,medicinal value,cultivation techniques,stress resistance and chemical composition,and the arguments of research on reproductive biology of L.davurica are relatively weak.In the study of ’ Jinnong No.1 ’ Dawulihuzhizi is used as the experimental material,combined with conventional paraffin sections,pollen in vitro culture method,fluorescence microscopy and scanning electron microscopy and other methods.The optimal conditions for pollen germination of L.davurica,flower organ morphology and pollen morphology,dynamic changes of pollen germination and growth on stigma,flower bud differentiation,microspore and male and female gametophyte development,double fertilization,embryogenesis and endosperm and mature seed structure are systematically studied.The results provide a scientific basis for the artificial cultivation and breeding of this plant,and basic data on reproductive biology for the systematic study of legumes.The results are as follows:(1)The pollen grains of Lespedeza daurica are observed by scanning electron microscope,from the polar view,there are three germinal apertures with polar axis lengths of 19.98 μm to 33.3 μm,and from the equatorial view,the pollen grains are super-long spherical,the average equatorial axial lengths of 10.2 μm to 16.5 μm,and the pollen exine ornamentation is network structure.In vitro pollen culture test,the optimal medium for pollen germination is 20 g·L-1 sucrose + 40 mg·L-1 boric acid+80 mg·L-1 calcium chloride,the optimal microscopic examination time is 6 h,the optimal sampling time is 12:00,the optimal culture conditions is 25°C under dark conditions and the optimal storage temperature is-20°C.This experiment shows that the pollen viability of L.davurica is generally high.In vitro liquid culture of pollen is an efficient,simple,fast and reliable detection method,suggestions for future research can be optimisation of the selection of culture conditions.(2)The morphology of pistils and stamens of L.daurica are observed by scanning electron microscope and optical microscope.The results show that some anthers are abortion or immature,and the surface of anthers is covered with papillary structure;stigma,style and ovary are covered with long flocculent villi,and the villi on stigma grow tortuously to reach a finger protrusions shape.The results of fluorescence microscopic observation show that there are more pollen attached to the stigma,but not many the pollen tubes entering the stigma,and some pollen tubes appearing callose competition and spiral growth during the growth process.There is gametophyte incompatibility in L.daurica,and the fertilization method is micropyle fertilization.(3)The flower bud differentiation stage of L.daurica lasted about 40 days,and the flower bud differentiation development is divided into 6 stages.The differentiation period and corresponding stages are as follows: the vegetative growth period begin in early May,and the flower bud differentiation period begin in mid-May;After that,the petal differentiation is carry out,and the sepal differentiation stage starts from mid-May to late May,and the petal primordium differentiation stage starts from late May.This is followed by the reproductive organ differentiation,stamen primordium which begins to differentiate from the end of May to early June,pistil primordium began in early June.(4)The anther wall development type of L.daurica is a basic type.The mature anther wall is composed of epidermis,endothecium,middle layer and tapetum,the tapetum development type is secretory type.When the anther matured,there is only one layer of endothecium,and the cells are banded lengthening in the development process.(5)The type of cytokinesis of microspore mother cell of L.davurica is simultaneous.After the second meiosis,microspore cells form a tetrad,which is arranged in two ways,namely left-right symmetric type and tetrahedral type.Fluorescence microscopic observation show that the microspores at the tetrad stage are surrounded by callose fluorescence,and the fluorescence phenomenon disappears after developing into free microspores.The mature pollen of L.davurica is 2-cell type.(6)The ovary of L.daurica has one chamber which has one ovule that is double integuments,tenuinucellate and anatropous,After meiosis,the megaspore mother cell divides into four megaspore,the arrangement of megaspore cells is linear,the megaspore in chalaza end usually is functional one,and uninucleate embryo sacs formed mature embryo sacs with seven cells and eight nuclei by mitosis.Therefore,the development mode of embryo sacs of L.davurica is polygonum bipolar type.(7)The fertilization of L.daurica is micropyle type,the primary endosperm nucleus is formed after central cell fertilization,and the development mode is nuclear type.The early endosperm nucleus is distributed at the edge of the embryo sac,with the division and proliferation of the nucleus,the free nucleus become endosperm cells and distributed around the embryo sac,after the zygote development to the spherical embryo,the endosperm cells began to degenerate.At the mature embryo stage,the endosperm cells are disintegrate and disappeared.The zygotes of L.davurica has a long dormancy time.First,the mitosis is carried out to form basal cells and parietal cells.Then,the basal cells are divided many times to form petioles,and the parietal cells formed embryo bodies.According to their external morphology,they can be divided into spherical embryos,heart-shaped embryos,torpedo-shaped embryos and mature embryos.The outer epidermis of mature seeds is developed from the ovule.The components of seeds include cotyledon,hypocotyl,germ,radicle and seed coat.