毛竹种子形成过程中形态解剖学特征

Morphological and anatomical characteristics of Phyllostachys edulis seeds during formation process

关键词:  毛竹种子, 胚, 胚乳, 果皮, 种皮

Key words:  Phyllostachys edulis seeds, embryo, endosperm, pericarp, seed coat

摘要:

为揭示毛竹(Phyllostachys edulis)种子生长过程中胚、胚乳、果皮及种皮的发育规律,以桂林海洋山一带的开花毛竹为材料,采集并固定不同时期的开花毛竹种子,使用石蜡制片法制片,显微镜观察胚、胚乳、果皮与种皮的结构变化。结果表明:(1)毛竹花后1 d完成受精并形成合子,合子休眠时长约为5 d。经过原胚阶段、胚芽鞘阶段、幼胚生长阶段及成熟胚阶段,花后40 d的胚发育基本成熟,其发育类型为禾本型。(2)胚乳发育早于胚的发育,其发育类型为核型胚乳,历经游离核、细胞化、细胞分化及成熟4个阶段。在细胞分化阶段胚乳细胞分化形成淀粉胚乳细胞以及糊粉层细胞,淀粉胚乳细胞主要积累淀粉粒,糊粉层细胞主要积累矿质元素、脂类及蛋白质等。(3)花后1 d的果皮细胞及珠被细胞形状规则、内含物丰富、结构完整; 花后10～20 d,内、外果皮及珠被细胞层数递减,形状发生改变,中果皮细胞开始出现淀粉粒; 花后20～60 d,随着胚乳细胞营养物质的积累及体积的增大,向外产生机械压力,中果皮细胞逐步消解仅剩残留的细胞壁; 外果皮细胞呈长条形,细胞壁加厚,与残留的中果皮细胞壁组成保护结构; 皮层在种子发育过程中主要起到合成、运输营养物质以及保护胚和胚乳发育的作用。该研究结果为完善毛竹生殖生物学相关内容以及了解竹类植物胚和胚乳的发育提供了理论依据。

Abstract:

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.