Novel Carrot Embryo-forming System.

我们开发了一种新的胚胎形成系统，在该系统中，胡萝卜体细胞胚胎的发生是在不含2，4-D的情况下从表皮细胞一步完成的，前提是下胚轴外植体在含有2，4-D的MS液体培养基中培养12-24小时。此外，在该系统中，体细胞胚胎直接通过贴壁于外植体的有组织的表皮细胞的重复分裂形成丛生细胞来发育，而不会对愈伤组织和悬浮培养细胞进行脱分化。扫描电子显微镜观察到胡萝卜表皮细胞直接发生体细胞胚胎发生。从亲本组织中剥离的表皮细胞以压缩细胞的形式存在，然后扩张成为管状细胞。随后，肾小管上皮细胞水平分裂成规则的线状簇状细胞，然后这些簇状细胞垂直分裂变大。线状簇状细胞通过不规则的斜面分裂形成肿胀结构，然后继续分裂形成小的原胚。一些细胞由肿胀结构表面和原胚组成，向四面八方扩张，覆盖在结构表面。这些膨大的细胞可能覆盖了一层结构的表面，并进一步堆积了细胞层，通过小的原胚形成了从肿胀到球形的胚胎。这些扩张细胞是在心期胚胎表面形成的。

We have developed a novel embryo-forming system in which carrot somatic embryogenesis takes place in a one-stage process from epidermal cells in the absence of 2,4-D,provided hypocotyl explants are incubated in a liquid MS medium containing 2,4-D for 12-24 hours. In addition, in this system, somatic embryos develop directly via formation of cluster cells by repeating division of organized epidermal cells with adhesion to explants, without dedifferentiation to callus and suspension cultured cells. Somatic embryogenesis occurred directly from carrot epidermal cells was observed using scanning electron microscopy.Epidermal cells peeled off from parent tissues were present as compressed cells and then expanded to become tubelar cells. Subsequently, tubular cells were regularly and horizontally divided to from linear cluster cells and then these cluster cells divided vertically to become enlargment. Swelling structure were formed by irregular and oblique division at places on linear cluster cells and then continued to divide to form small proembryos. Some cells which comprised surface of swelling structure and proembryos expanded to every direction to become covered on surface of structure. These expanding cells made probably put a layr of surface of structure and furthermore piled up cell layr to form from swelling to globular-stage embryo via small proembryo. These expanding cells were formed on surface of heart-stage embryo.