Jegla D E, Sussex I M
Department of Biology, Yale University, New Haven, Connecticut 06511.
Dev Biol. 1989 Jan;131(1):215-25. doi: 10.1016/s0012-1606(89)80053-3.
We mapped the fate of cells in the shoot meristem of the dry-seed embryo of sunflower, Helianthus annuus L. cv. Peredovic, using irradiation-induced somatic sectors. We analyzed 249 chlorophyll-deficient or glabrous (hairless) sectors generated in 236 plants. Most sectors observed in the inflorescence extended into vegetative nodes. Thus cell lineages that ultimately gave rise to reproductive structures also contributed to vegetative structures. No single sector extended the entire length of the shoot. Thus the shoot is not derived from one or a few apical initials. Rather, the position, vertical extent, and width of the sectors at different levels of the shoot suggest that the shoot is derived from three to four circumferential populations of cells in each of three cell layers of the embryo meristem. Sectors had no common boundaries even in plants with two or three independent sectors, but varied in extent and overlapped along the length of the shoot. Thus individual cells in a single circumferential population behaved independently to contribute lineages of different vertical extents to the growing shoot. The predicted number of circumferential populations of cells as well as the apparent cell number in each population was consistent with the actual number of cells in the embryo meristem observed in histological sections.
我们利用辐射诱导的体细胞扇形区，描绘了向日葵（Helianthus annuus L. cv. Peredovic）干种子胚的茎尖分生组织中细胞的命运。我们分析了236株植物中产生的249个叶绿素缺乏或无毛（无毛）扇形区。在花序中观察到的大多数扇形区延伸到营养节。因此，最终产生生殖结构的细胞谱系也对营养结构有贡献。没有一个扇形区延伸到茎的全长。因此，茎不是由一个或几个顶端原始细胞衍生而来。相反，茎不同水平处扇形区的位置、垂直范围和宽度表明，茎是由胚分生组织三个细胞层中每一层的三到四个圆周细胞群衍生而来。即使在具有两个或三个独立扇形区的植物中，扇形区也没有共同边界，而是在范围上有所不同，并沿茎的长度重叠。因此，单个圆周细胞群中的单个细胞独立发挥作用，为生长中的茎贡献不同垂直范围的细胞谱系。预测的圆周细胞群数量以及每个群体中的表观细胞数量与组织学切片中观察到的胚分生组织中的实际细胞数量一致。
