Comparative Study On The Gametophytes And Embryological Development Of Isoetes Yunguiensis And I.Sinensis

Isoetes yunguiensis and I.sinensis belong to herbaceous fern of Isoetaceae, They areChinese specialty quillwort. Isoetes yunguiensis are mainly distributed in upper of theYangtze River, Yunnan and Guizhou. Isoetes sinensis is an old endemic species frommiddle and downside of the Yangtze River. Isoetes ability to adapt to theenvironment is poor, and extremely sensitive to environmental. Isoetes are endangered.The five types of our country Isoetes have been listed as national key protected wildplants in the critically endangered. This paper selects the two types as the experimentalmaterial, so that comparing their morphology in the course of development,understanding the biological characteristics. The article provides basic data for thepopulation rejuvenation and ex situ conservation, also investigates the mechanism ofreproductive biology of endangered.This paper uses artificial cultivation method of spores. With the continuous paraffinmethod, semi thin sectioning, ultrathin sectioning, SEM and LSCM, This experimentwere observed the development of gametophyte, embryos and sporophyte in Isoetesyunguiensis and I. sinensis. The observed results are as follows:Microspore is monolete, and macrospore is trilete. Isoetes is a special type ofheterosporous ferns. Macrospore ornamentation of I. yunguiensis is cristate-reticulate,proximal face of megaspores have incomplete network ornamentation; Proximal surfaceornamentation of micropore became short spiny, protuberance on distal face. Proximalface of I. sinensis macrospore is circular, ornamentation is irregular network; a regularnetwork ornamentation on distal face.Mature archegonia are brown in two Isoetes. The archegonium consists of16neckcells, one neck canal cell, one ventral canal cell and an egg. The archegonium is anearly spherical individual. The number of archegonia is the most where macrosporetrilete. Gametophytes of two types belong to intramural development type.First division of zygote splits paralle with archegonium transverse axis in I.yunguiensis. First division of zygote deflects angle of20degrees with archegoniatransverse in I. sinensis. Split horizontal is high left and low right. There are two orthree nuclear phenomena of zygote in I. yunguiensis, I. sinensis has not found so far.The embryonic development of two kinds of Isoetes are consistent with no suspensor inward development type, namely that zygotic cleavage is perpendicular to the directionof gravity.The growth sequence of sporophyte in two kinds of Isoetes is leaf faster than root.When the first leaf through the female gametophyte to a certain length, root just out ofgametophyte surface. The growth direction of the first leaf and the root is opposite. Rootdevelopment of two kinds of Isoetes belongs to the inner origin. Two fork roots divisionhas begun in early developmental stage, the two parts of the apical meristem division atdifferent speeds.Bulb has developed vascular tissue, which includes xylem and phloem. Xylemconsists of parenchyma cells and tracheid, tracheid has thread or mesh shape; Thephloem cells of different sizes, cells darker.The numbers of intrastelar canal of leaves are3, no found Casparian strip structure.Velum was found in the early development of I. sinensis, but velum finally disappeared.In the development process of seedlings and plant of I. yunguiensis are found no velum.Ligule grows above sporangium, labium grows between ligule and sporangium.Ligule length, glossopodia size has certain difference in two species of Isoetes. In theearly development of plant, ligules and leaves of two species of Isoetes grow at thesame time; the growth rate of ligule even faster than leaf’s, ligule maturates earlier thanleaf.This observation compares reproductive developmental characters of two species’slife history, which includes the development of gametophyte, embryo and sporophyte.It’s providing the basic data for the sexual generation process of domestic type, andproviding theoretical basis and technical support for reproductive biology mechanismand endangered mechanism of Isoetes.