银杏种子内种皮解剖学复合结构特征

Compound characteristics of the endotesta of Ginkgo biloba seed in anatomy

为进一步了解银杏成熟种子的内种皮特征,通过徒手切片和石蜡切片,对银杏胚珠到种子的个体发育过程进行解剖观察.结果表明,银杏成熟种子内种皮是棕色膜质的复合结构,内种皮远轴半部和近轴半部之间,以及远轴半部的内外之间,分别由个体发育来源不同的部分组成;远轴半部的内种皮由内膜层、外膜层和两膜层之间的种腔组成,而近轴半部的内种皮只有1膜层.种子在发育成熟时,在远轴半部,原胚珠的珠心层没有完全消失,而是成为内种皮的内膜层,胚珠腔直接成为种腔,珠被内区成为内种皮的外膜层;在近轴半部,胚珠的雌配子体之外的邻近组织区成为单膜层的内种皮.此外,观察到银杏幼种子远轴半部珠被内区的储水组织更为详细的特征,但在银杏胚珠或种子内,除基部外,没有见到维管束.

There is still inconsistent or deficient realization on the anatomical character of the endotesta of Ginkgo biloba seed in the relevant literature.In this paper,a An anatomical and ontogenical observation was conducted on the ovule to the mature seed using freehand and paraffin sectioning methods,in order to further understand the characteristics of the endotesta in the mature seed of Ginkgo biloba.The results revealed that the endotesta of mature seed is a compound structure of brown membrane consisting of origin-different parts in ontogeny and anatomy,between the distal and proximal halves,and between the interior and exterior of the distal half of the seed;in the distal half,the endotesta is composed of an inner membranous layer,an outer membranous layer,and a seed-cavity in between,but in the proximal half,only one membranous layer.While the seed matures,in the distal half,the nucellus layer of its previous ovule does not completely disappear,and becomes a part as the inner membranous layer of the endotesta of the mature seed,simultaneously the ovule-cavity is straightly retained as the seed-cavity,and the inner zone of the integument becomes the outer membranous layer of the endotesta;in the proximal half,the tissue zone adjacent to the megagametophyte of the ovule becomes the membranous endotesta as a single layer.Moreover,in the distal half of the young seed,the more detailed characteristics of the water tissue originating from the inner zone of the previous integument were observed,however,no vascular bundle was seen in the main body of the ovule and seed except the base.