| Eustoma grandiflorum grown as a commercial cut flower has highly decorative characteristics with a variety of flower color and form. It's a good material for embryological study since there are 2000 to 3000 ovules in an ovary. This research provides basic information for genetics and breeding of this plant. A breeding line "02-49"of E. grandijlorum with yellow single flowers was used because it was almost genetically pure due to self-fertilization for many years, a flowering period was long and hereditary traits were stable. In December of 2003 and 2004, seeds were sown in a greenhouse kept at 7 to 15°C at Research Institute of Flower Biotechnology, Northeast Forestry University. Next year 500 seedlings were chosen and replanted for growth. Flowers were sampled from plants 60cm high in July to August when temperature in a greenhouse was 15-30°C. More than 500 flower buds or flowers on the second or third lateral branches were taken at 10 growth stages ranging from 0.2 to 4cm in bud length. Microsporogenesis, megasporogenesis, and the development of the male and female gametophytes were observed microscopically. After manual flower pollination. 5 to 10 styles and ovaries on the second or third lateral branches were taken at different developmental stages;at interval of 2 hours during first 48 hours after pollination, at interval of 4 hours for next 48 hours, and at 2 or 3-day interval thereafter to 60 days after pollination. Fertilization process, and the development of the embryo and endosperm were observed microscopically. Materials were fixed in FAA (5 mL formalin : 6 mL acetic acid : 89 mL 70% ethanol). After stained with Ehrfich's haematoxylin, the fixed tissues were embedded in paraffin using a conventional method, and cut at a thickness of 6 to 10μm. More than 2000 slices were prepared with 10 to 20 continuous sections each slice. Observation and photomicroscopy of sections were carried out using a light microscope (Olympus. BX15). The results are as follows.1. Anther walls were consisted of six layers of epidermis, endothecium, three middle layers and tapetum. Formation of anther walls was of the Dicotyledonous type. The tapetum was of heteromorphic and glandular type.2. Cytokinesis in the microsporocyte meiosis was of the simultaneous type. Microspore tetrads were tetrahedral or medianly zygomorphic. Mature pollen grains were 2-celled and had3 germ furrows.3. The ovary was bicarpellary syncarpous and unilocular having parietal placentas. Ovules were anatropous. tenuinucellatae and unitegmic. The archespore under the nucellar epidermis developed directly a megaspore master cell, which in turn underwent meiotic division to form4 megaspores arranged in a line or a T-shape. The chalazal megaspore was observed functional.Before fertilization, the 2 polar nuclei fused into a secondary nucleus. The mature embryo sac was made up of 7 cells. The formation of the embryo sac was of the Polygonum type.4. Wet stigma and inapertus style with transmitting tissue were observed. Pollen tubes passed the stigma and came into the style. The genital cell in the middle or inferior part of the style was divided into 2 sperm cells. As for porogamy, the pollen tube entered the embryo sac and destroyed one of two synergids to release 2 sperms in the micropylar end. A sperm fused with the egg cell to form a zygote, which finally formed an embryo. Another sperm fused with the secondary nucleus of a central cell to form a primary endosperm nucleus and then formed endosperm. The fusion of a sperm nucleus with a polar nucleus is faster than that with an egg cell. Double fertilization is the type of the Premitotic gametogamy.5. Dormant stage of the zygote is about 15 days long, and then divided into a two-cell proembryo. Embryogeny followed the Solanad type. After the developmental stage of clavillose embryo, globular embryo, heart-shape embryo and torpedo-shape embryo, they finally became the mature embryo. In seeds, there were torpedo-shape embryos. The development of endosperm belonged to the nuclear type.
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