Floral Biology And Development Of Female And Male Gametophyte In Tapisicia Sisnensis Oliver

Tapiscia sinensis Oliv.which belongs to Tapiscia in Staphyleaceae is a kind of age-old tree which survives from tertiary,it is a rare and endangered plant endemic to China.It is mainly sparse distributed in the south of Yangtze River and southwest each province(area).In province of shaanxi it is mainly distribute in the north slope of Basan mountains,south slope of Qinling Mountains,east and west forest region in Ningshan.Because it's periods of sexual reproduction keep on 17 months,the natural renewal ability is weak,the natural wood is chopped down,the wild plant reduces increasingly.There have had many reports about Tapiscia sinensis Oliv on the taxonomic state,morphological characteristics,ecological characters,pharmacology, resources exploitation,propagation technique and cultivation in recent years.While, there are few reports on the biological characters of the seeds,especially,there are no reports about embryology of Tapiscia sinensis Oliv.The aim of present study was to systematically study the megasporogenesis,microsporogenesis and development of male and female gametophytes,the development of embryo and endosperm in Tapiscia sinensis Oliv with method of semi-thin section and serial paraffin sections. And we also studied its floral biology and the development of fructification in order to provide scientific basis and new materials on cultivation and biological charaters of Tapiscia sinensis Oliv.The results are as follows:1.The flower's characteristic of Tapiscia sinensis Oliv.The flowers of Tapiscia sinensis Oliv is small,yellow,arrange tightness and radial symmetry,They are androdioecism.The male flower has five stamens which could normal develops,but its gynoecium has degenerated.The bisexual flower have a normal gynoecium,but its mature pollen in five stamens is abnormal which haven't vegetative cell and spindly generative cell.We think the flower of Tapiscia sinensis Oliv is original unisexual flower,and the bisexual flower is female flower which is male sterile.2.Floral biology of Tapiscia sinensis Oliv. Through we observe to male flowers,bisexual flower,anthotaxys of male flower, anthotaxys of bisexual flower of Tapiscia sinensis and record florescence,the results are as follows:the flowers of mature Tapiscia sinensis in area of Xi'an begin to bourgeon in early April each year,blossom from May 25 to about June 10,the florescence is about 20 days,the wild Tapiscia sinensis in area of Qinling blossom late 20 to 30 day than in area of Xi'an.The visiting insects is very few and basically is flies,we think the flower of Tapiscia sinensis is anemophilous flower.In different parts of flower development is not synchronized,the inflorescence develope faster in the lighting location and the time of blossom early 1 to 2days;in different parts of fruit development is not synchronized,the fruit develop faster in the lighting location which early 3 to 5 days than in the shade.Tapiscia sinensis always have been thought to blossom two times in a year by mostly scholar,the first time from February to March in early spring each year,in this time the flower is bisexual flower,seed after flowering;the second time from June to July each year,in the time the flower is unisexual flower,no seed after flowering. Through our study of floral biology of Tapiscia sinensis,the results are as follows: The flower blossoms in late May,and is fertilized in early June.Then the zygote immediately goes into dormancy before any cell division,and this status is maintained until next March.The dormant young fruit has several characters adapted to winter survival,such as cork layer formed on ovary surface and receptacle enclosing the fruit stalk etc.The fruit does not start developing until next April.Afterward it enlarges rapidly and completes its maturation by the end of September.Its extreme long sexual reproductive cycle is due to the zygote dormancy.Therefore the fruit of the preceding year and the flower of this year appear on the same branch in the summer.3.Microsporogenesis and development of male gametophytesThere are four microsporangiums in Tapiscia sinensis Oliv.The structure of anther primodium is very simple,its outmost layer is epidermis and the inner layers are a group of active meristem cells.Then the antherogenous occurres because the outside cells at four corners divide quickly.A group of archesporial cells are formed interior to epidermis at each corner.The archesporial cells divide periclinally to form primary sporogenous cells and primary parietal cells.Primary parietal cells divide periclinally into four layer cells of the anther wall,which continue to growing and become into epidermis,endothecium(1 layer),middle layer(2 layer,disappeared earlier)and tapetum(1 layer).During the meiotic prophase I of microspore mother cells,the nucleus of tapetum divides into two.The cells of tapetum are glandular and secrete many fat-sphere bodies into pollen sac.The primary sporogenous cells develop into microsporocyte by mitosis.The microsporocyte undergoes simultaneous meiotic division and produces tetrahedral tetrad.The tetrad is tetrahedral arrangement and surrounded by callose.Then the tetrad is separated by callose decomposition and each of them is a microspore which develops into the mature pollen who is 3-cell type.At this time,the anther wall just is consisted of epidermis and endothecium.With the spliting of the wall between neighbor anther sacs,the mature pollens are spilled out.4.Megasporogenesis and development of female gametophytesThe ovary of Tapiscia sinensis Oliv.is anatropous,double integuments and crassinucellate.Megasporogenesis is started from an archesporial cell under the nucellus epidermis.The archesporial cell is different from other nucellus cells with large volume and dense cytoplasm and a big nuclear.The archesportial cell divides one periclinal cell and one primary sporogenous cell,the primary sporogenous cell develops into megaspore mother cell directly.The megaspore mother cell undergoes meiosis to form triad in line type or rarely four megaspore in line type.Normally,the chalazal megaspore functions and forms the female gametophyte,but sometimes the second chalazal megaspore also functions.During 8-nuclei embryo sac stage,there are two synergids and one egg at the micropylar end of embryo sac.The egg has a large vacuole at the chalazal end and a nuclear at the micropylar end.The synergids are kept during two polar nucleus are fusing together.Two polar nucleuses are located at the center part of the embryo sac and they have different orientations,sometimes they are at transverse direction,sometimes at longitudinal direction,and sometimes at oblique direction.There are three antipodal cells at the early stage of megasporogenesis. They degenerates with the development of embryo sac.after two polar nuclei fused,the secondary nucleus moves to chalaza end,attached on bowl protuberance in chalaza end,this is a peculiar structure in its development.