Research On Life History Of Isoetes Sinensis (Jiande Population) And I. Taiwanensis

Isoetes L. is the survivors of Isoetaceae, belong to the quasi ferns, existingmore than100kinds around the world, represents a unique evolution route in higherplants, with high value of systematics study. Since last century30s, there areresearch results published continually about genetics、reproduction、cytology、physiology、biochemistry、molecule of Isoetes. But, system ascription problemabout Isoetes is still in exploring, without an accurate conclusion. In the territory ofChina, population quantity of Isoetes is declining, at present, all kinds of the Isoeteshas been listed as the National level to protect plant, therefore, domestic scholars inaddition to the keen on the study of the value of Isoetes system, also urgently hopeto find out the cause of Isoetes endangered from the point view of life history,especially reproduction, and to bring forward conservation countermeasures. For allthe above reasons, this article selects Isoetes sinensis(jiande population) and Isoetestaiwanensis as the experiment material, with the soil culture method、water culturemethod and Knop’s solid medium culture method to cultivate spores and seedlingsof this two kinds of Isoetes. According to the characteristic of gametophyte、embryoand sporophore, select the typical and stable experimental materials to fix. With themethod of paraffin section、semithin section、ultrathin section and LCSM scan toobserve the experimental materials. The results are as follow:In the process of the female gametophyte development of Isoetes sinensis andIsoetes taiwanensis, the nascent nuclear become many free nuclei after manynuclear division, after the cell wall of the free nuclei formed, gametophyte mature,afer the first archegonium formed, the megaspore will dehiscence, fulvousarchegonium will be exposed. The rhizoid of female gametophyte in Isoetessinensis(jiande population) is transparent, the female gametophyte of Isoetestaiwanensis with out rhizoid. Abundant archegonium produce at the same time inthe same female gametophyte, but the archegonium of the Isoetes taiwanensisusually abortive for the reasons of neck cell degeneration or egg dissolution. Thefirst split direction of the zygote often at20°angles to the archegonium axis, afterthe period of spherical embryonic, the first leaf blade original cell and the first rootoriginal cell will differentiate from the top of embryo and the bottom of embryo, thefirst leaf blade original cell development into first leaf blade primordium rapidly,and the first root original cell development into first root primordium rapidly too, the development of the first leaf blade primordium faster than first root primordium,the first leaf blade primordium break through the calyptra firstly, development intothe first leaf blade，after the second leaf blade primordium and the second leaf liguleprimordium formation, the first root primordium development into the first root.Anatomical observation the sporophyte of this two kind Isoetes. Find that theaerenchyma of the root will dissolve in the process of development in Isoetessinensis(jiande population), the mature root of the Isoetes sinensis(jiande population)and Isoetes taiwanensis consists of epidermis、cortex、connection cells、the centralvascular bundle; during the process of the stem development, there is a cavity willproduce in the center of the stem gradually, the mature stem of the Isoetessinensis(jiande population) and Isoetes taiwanensis consists of epidermis、cortex、lateral meristem、secondary vascular tissue and primary xylem; mature leaf blade ofthis two kind Isoetes consists of epidermis、cortex、the central vascular bundle、peripheral vascular bundle、air passage and thoracic diaphragm, the mature leaf bladewith2air passages in the young sporophyte of Isoetes sinensis(jiande population),but there are4air passages in the sporophyte that with15leaf blades or above,there are3central tracheid in the center of vascular bundle, but there is a singletracheid in the center of vascular bundle. The leaf epidermis cell with quadrateshape in this two kind of Isoetes, the cells with irregular shape that around thestomata, stomata have guard cell, no subsidiary cell.In the sporophyte that with15leaf blades，sporangium will produce gradually.In the early differentiation of the sporangium in Isoetes sinensis(jiande population),it is difficult to distinguish megasporangium and microsporangium,megasporangium and microsporangium difference gradually after themegasporocytes formation. Except the volume of the sporangium in Isoetestaiwanensis smaller then the sporangium in the Isoetes sinensis(jiande population),there was no obvious difference in appearance. The surface ornamentation withthe shape of ridge in Isoetes sinensis(jiande population), The surface ornamentationwith the shape of tuberculate, the subsurface ornamentation of this two kindsmegaspores are with the shape of fibrillar; the surface ornamentation and thesubsurface ornamentation with the shape of spininess in this two kinds microspore.By observing the development process of gametophyte、embryo and sporophyte,found out the typical and stability characteristics of the life history in Isoetessinensis(jiande population) and Isoetes taiwanensis, Discussed the origin order of root、stem and leaf blad, analysis the developmental mechanism of the nutritiveorgan from the view of anatomia, provide objective and stable life history materialsabout the sdudy of Isoetes. Analysis the endangering cause of Isoetes, and came upwith homologous protection countermeasures.