野芹菜体细胞胚胎发生早期变化的细胞学研究

通过光学与电子显微镜观察研究了野芹菜(Angelica polymorpha Maxim.)叶柄外植体胚性细胞的起源与原胚状体的发生。叶柄切段植入 MS 2mg/L2,4-D 0.25 mg/L KT固体培养基后,以DNA合成和细胞分裂为指标,判明了胚状体发生与紧贴维管束的鞘细胞层密切相关;鞘细胞通过有丝分裂形成多层结构的细胞群,它们仍含大液泡及薄层胞质,成片被覆在维管束表面;胚性细胞团即不同步地发生在该多层组织较内层的局部位点上,细胞具大核,胞质稠密,经持续有丝分裂发展成大小不同呈瘤状突起的原胚状体。伴随着鞘细胞的剧烈变化,韧皮部薄壁细胞亦分裂增殖,原有筛管变形衰退,部分新增殖的细胞分化为新筛分子;木质部中,原导管束附近朝向韧皮部一侧的部分薄壁细胞亦进一步分化为孔纹导管。外植体中维管系统的再次分化,显然是与输导功能强化以适应原胚状体发生时对营养物质的大量需求有关。

CYTOLOGICAL STUDIES ON THE EARLY PHASE OF SOMATIC EMBRYOGENESIS IN PETIOLE EXPLANTS OF WILD CELERY

The wild celery (Angelica polymorpha Maxim.) was employed as the experimantal ma- terial to study the initiation of the embryogenic cells and the ontogeny of the proembryoids in petiole explants examined with light and electron microscopy. Segments of petioles were cul- lured on the surface of MS medium (MS 2,4-D 2mg/L KT 0.25mg/L), and then the DNA synthetic activity and cell divisions were examined to confirm that in which cell depar- ture from quiescent state and initiation of cell division occurred. Results show that the proe- mbryoids originate from the innermost layer of cortex parenchyma cells which exhibit rapid periclinal and anticlinal divisions, then a pericyclic tissue composed of 2-3 layers of smaller but still vacuolate cells form and corrugately cover the vascular bundle. Soon after that, indi- vidual cell groups located in the inner region of this tissue undergo regressive change and asyn- chronously transform to embryogenic clusters, giving rise to nodule-like proembryoids by re- peated cell divisions. Meanwhile, the phloem parenchyma cells also proliferate by mitosis. Ac- companying with some original sieve tube degeneration, a number of new sieve elements diffe- rentiated from the newly formed parenchyma cells. Microscopic observations also reveal that a lot of new tracheary elements differentiated from the xylem parenchyma cells. Evidently, the re-differentiation of the vascular elements in the petiole explants reflects the intensification of nutrient translocation in these segments in close relation to the great demand for nutrients du- ring the ontogeny of proembryoid.