Study On The Reproductive Biology Of Soybean

Soybean is a type of annual herbaceous plant, whose flower is racemose. It is a versatile strategic crop, which isdistributed all over the world. Soybean, rice, corn and wheat are the four major food crops in China.This paper studies the megasporgenesis, the development of megagametophyte and pollen tube growth ofsoybean Glycine max (L.) Merr. cv. Dongnong46(Leguminosae). Three kinds of techniques were applied to observeit, scanning electron microscopy, transmission electron microscopy and fluorescence microscope. Aimed atunderstanding the action mechanism and ultrastructural changes on the characteristics of soybean embryonicdevelopment comprehensively. And also supplementing useful information in soybean developmental biology; In thesame time, providing a scientific basis for soybean breeding and production. The following are the results of theproject:1. Stigma of soybean had two types of papillae on the mature stigma surface covered by a pellicle. The two typesof cytoplasm of papillae were dense. There were a large number of mitochondria, lipid, endoplasmic reticulum (ER)and ribosomes in papillae cells. Stigma cells were rich in organelles and there are deposition of electrondense storagematerial within the vacuole.2. Soybean has a hollow style. The style closing to the stigma reversed into "J" shape. There are pores at thebase of the style. Stylar canal occupied the center of the style, which was around by a layer of special passage cell.Besides, there were plenty of polysaccharides in mature cells of the style.3. The outer integument was3-4celled thick and the cells were mostly straight and regularly arranged. Thevacuoles were large and there were deposition of electrondense storage material within the vacuole. The innerintegument was2-celled thick and the cells were mostly square. The cells of the inner integument were characterizedby dense cytoplasm, abundant mitochondria, ER, Golgi and few small vacuoles. The cytoplasm was strong andabundant with small vacuoles, the mitochondrial and ER, which were more scattered near the cell wall.4. Megasporogenesis originated from archesporial cell, which lied under nucellus epidermis. Themacrosporocyte developed from the sporogenous cell directly, which lied under nucellar cell. The macrosporocytewere irregular in shape with a large number of small vacuoles. Arrangement of megaspore was linear shaped at tetradstage and the megaspore of chalazal end was functional megaspore finally.5. Development of megagametophyte started from the mono-nucleate embryo sac formation stage. Thecytoplasm was increased and the vacuole became bigger. Finally, they developed into the mature embryo sac with7cells containing8nuclei. Egg Apparatus cells densely were filled with cytoplasm; the central cell were vacuolated;antipodal cell at the end of chalazal were degenerated. At the same time, the nucellar cells showed the indications ofdeath of programmed cell.6. The cytoplasm of pollen grains was dense and the notable features of the cytoplasm was the numerous amyloplasts and plastids. Most pollen grains started to germinate on the stigmatic surface immediately afterpollination, following with the elongation of the pollen tube. Within1hour, the pollen tube was longer than thediameter of pollen grain through the stigma; at3-4hours, most pollen tubes grew into the middle of the styles, andthen continued to elongate in the ovary until6hours after self-pollination.7. Conspicuous changes were observed in the style after the fertilization. Passage cells were arranged un-regularly and the spaces between the cells were much enlarged. This stage of stylar development was filled withdensely stained secreted materials after the fertilization along the pollen-tube pathway in the style. They secreted aglobular exudate which is similar in appearance to that of the stigma.