Study On Embryology Of Ulmus Pumila L.

Ulmus pumila L.belongs to the Ulmus plant of Ulmaceae.It has a high economic value,can be used as medicine is also a good timber species.In this study,the development of spore,male and female gametophyte development,fertilization,development of embryos and endosperm were studied by means of optical microscopy.The main results are as follows:(1)The anther is composed of four pharmacies.The development of anther wall is dicotyledon type,from external to internal successively: 1 epidermis layer,1 endotheca endotheciume layer,1 middle lamella layer,1 tapetum layer.The tapetum belongs to the multicore glandular tapetum type,and the dissolution is made in situ when the microspore mother cell developed into the tetrads,mature pollen walls are only fibrous layers and partially remnant of the epidermis.(2)The microspore developed from meiosis of microspore mother cell.Cytokinesis is of the simultaneous type.The microspore tetrads are tetrahedral type and symmetrical type.The mature pollen belongs to 2-cell type with 4-7 germination holes.(3)The ovary consists of 2 carpels with a single locule,parietal placenta,anatropous ovule,double integument,and thick nucellus.In rare cases,two locule are visible.Ovule's development is slightly later than anthers,and ovules begin to develop when microspore sporogenous cells have been formed.The formation of megaspore mother cells from the great spore spore germ cell differentiation.The tetrad of megaspores is linear or T-type in arrangement,and a total of 1 megaspore is reserved for functional megaspore.(4)The embryo sac is of single-spore Polygonum type.The ovules of the bead end consist of one egg cell and two helper cells,and the end point contains three antipodal cells,and the central part of the embryo is a central cell with two poles.Egg cell and sperm cell to form a zygote,zygote experienced a long dormancy;central cell and sperm cell to form the primary endosperm nucleus,then into the split stage.(5)The embryogenesis conformed to the So-lanad type.After the activation of the zygote,experiencing the embryonic stage the early spherical embryo,the spherical embryo,the heartshape embryo,the torpedo-shape embryo and the mature cotyledon embryo were found in the mature seed.The endosperm type is karyotype,cotyledon embryos failed to observe the endosperm,which belongs to the endosperm-free seed.In recent years,the study of various aspects of Ulmus pumila L.research in progress,but the embryology research has not been reported.Through the research of this paper has made up the gap in the study of embryo research for it,for the genetic breeding and cultivation provide the basic information.The embryonic developmental characteristics provide a theoretical basis for the evolution of Ulmaceae.In order to make full utilization of resources.