Study On The Division Of Free Nuclei Of Wheat, Barley And Rice Endosperm

The endosperm of wheat, barely and rice all belongs to nucleus types, that is to say, the endosperm development need cross two periods—first nucleus period and then cell period. The division of nuclei belongs to nucleus period. Structure and division process of free nuclei of endosperm of rice, wheat and barley were observed by the methods of total dissection and resin-embedding sections. In addition, the factors affecting the division of nuclei were also ascertained. The results of the study would be helpful to clarify the diversity of division way of free nuclei,the rule of quality descendiblity in cereal,the factors affecting the division of free nuclei. The main results were as follows:(1) On the first day after flowering, the division way of the free nuclei in wheat, barley and rice was mainly mitosis. On the second day, there were two ways of division: amitosis and mitosis. The mitosis had two ways: one way was that firstly nucleolus elongated, the center constricted and meanwhile the nucleus also elongated until one nucleus devided into two; another way was that firstly one nucleolus divided into two , then karyotheca formed between two nucleolus and at last two nuclei formed.(2) There was no absolute boundary between mitosis and amitosis. The free nuclei produced by mitosis could proliferate by amitosis, the free nuclei produced by amitosis could also proliferate by mitosis. The phenomenon that two sister free nuclei began to proliferate by amitosis immediately before they separated from each other was found in rice. Such proliferation way could accelerate the proliferation of free nucleus.(3) The chromosome of free nucleus in barley is mainly triploid, while a few of chromosome wasn't triploid. It could be infered that the quality of endosperm might not be related to the quantity of chromosome.(4) The first two days after flowering, the antipodal cells proliferated with free nuclei of wheat, barley and rice at the same time. On the first day after flowering, the antipodal cells proliferated by mitosis and on the second day after flowering proliferated by amitosis. The antipodal cells began to disaggregate when free nuclei proliferated heavily, so it could be infered that the production disaggregated by antipodal cells provided nutrition for the development of free nuclei.(5) Low temperature obviously restrained the proliferation of free nuclei and also prolonged the time of proliferation; proper high temperature could enhance the velocity of proliferation and also shortened the time of proliferation, which could advance the process of becoming endosperm cells.(6) The nitrogenous fertilizer used at the stage of elongating , tillers and booting could obviously accelerate the division of free nuclei in rice, while there was no obvious effect on the division of free nuclei in wheat and barley.(7) The treatment of water stress conducted from the stage of planting to booting could increase free nuclei in rice.(8) The quantity of free nuclei would increase in wheat and rice when half of each leaf was removed, while free nuclei would also increase in wheat when the top seeds and the bottom seeds were removed.(9) There was no obvious difference in the number of free nuclei between yang12 and yang15 in wheat, while there was obvious difference in the number of free nuclei properly caused by different temperature during flowering between yang6 and jing9538 in rice.(10) There was obvious difference in the number among the free nuclei one to three days after flowering in wheat inseminated by stages.(11) Under tissue culture for three days after flowering, free nuclei of the wheat could develop as well as those lived in the field.