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The developmental patterns of the embryo, endosperm, pericarp, and seed coat during the growth process of Phyllostachys edulis seeds were revealed in this study, flowering P. edulis was used as the material in the Haiyang Mountain, Guilin, seeds at different stages were collected and fixed. Paraffin sectioning method was employed, and the structural changes of the embryo, endosperm, pericarp, and seed coat were observed under a microscope. The results were as follows: (1) Fertilization and zygote formation in P. edulis were completed within 1 d after flowering, and the zygote entered a dormant period lasting about 5 d. The embryo underwent the stages of proembryo, coleoptile stage, embryonic growth, and mature embryo, and reached basic maturity after 40 d post-flowering. The developmental type of the embryo was categorized as monocotyledonous. (2) The endosperm developed earlier than the embryo, and its development type was categorized as nuclear endosperm, which went through four stages: free nuclear, cellularization, cell differentiation, and maturation. In the stage of cell differentiation, starch endosperm cells and aleurone layer cells were formed. The starch endosperm cells mainly accumulated starch granules, while the aleurone layer cells mainly accumulated mineral elements, lipids, and proteins, etc. (3) One day after flowering, the cells of the pericarp and seed coat exhibited regular shape, rich in contents, and intact in structure. From 10-20 d after flowering, the number of layers of endocarp and ectocarp and seed coat decreased, the shape changed, and starch granules began to appear in the mesocarp cells. From 20-60 d after flowering, as the nutrient substances of endosperm cells accumulated and their volume increased, mechanical pressure was exerted outward, resulting in the gradual dissolution of mesocarp cells, leaving only remnants of cell walls. The ectocarp cells were elongated with thickened cell walls, forming a protective structure together with the remaining cell walls of the mesocarp cells. The cortex played a crucial role in synthesizing and transporting nutrients, as well as protecting the development of the embryo and endosperm throughout the seed development process. The results of this study provide a theoretical basis for improving the reproductive biology in bamboo species and understanding the development of embryo and endosperm in bamboo plants. |
