向日葵离体孤雌生殖过程的组织化学研究

HISTOCHEMICAL STUDIES ON IN VITRO PARTHENOGENESIS IN HELIANTHUS ANNUUS L.

对向日葵未受精胚珠培养所诱导的孤雌生殖过程进行了DNA、RNA、蛋白质与多糖的组织化学研究,同时也观察了体内胚胎发育的相应变化以作比较。离体孤雌生殖原胚发生初期的组织化学特征和体内合子胚相近;其中,卵细胞质中嗜派洛宁颗粒和卵核中孚尔根反应的动态值得注意。在后期,离体孤雌生殖胚状体和体内合子胚在淀粉动态上呈现显著的差异,这可能是前者不能顺利分化时的一种生理表现。

In recent years haploid sunflower embryoids were induced in our lab by culture of unfertilized ovules and these were revealed to be originated from the egg cells, i.e. via in Vitro parthenogenesis. The present paper reports some preliminary results of our histochemieal studies on this process. Ovules 1-2 days prior to anthesis were cultured on liquid N6 medium supplemented with 2 ppm MCPA, 6% sucrose and 100 ppm inosi- tol. Samples were fixed at intervals in aceto-methanol (1:3) and processed by paraffin method. In (?)ivo ovules were also collected at intervals before and after anthesis and processed in the same way serving as a control system. The sections were stained by Feulgen’ reaction far DNA(Plate Ⅰ, 1-6), methyl-green pyronin method for RNA(Plate Ⅰ, 7-12), mercuric bromphenol blue for protein (Plate Ⅱ, 13-18), and PAS reaction for polysaccharide (Plate Ⅱ, 19-24). The nearly matured egg cells were characterized by negative Feulgen reaction of the nucleus, negative pyronin staining of the nucleolus, abundant pyroninophylic granules in the cytoplasm, rich cytoplasrnic protein, but without starch grains. After fertilization, or when parthenogenesis was triggered, the cells of the early proembryo maintained weak Feulgen stain and pyroninophylie granules for a period, which indicated that the RNA synthesized formerly in the egg might play a role in early proembryo development until new transcriptional program was established. Although the early status of the in Vitro parthenogenetic proembryos was similar to that of the in Vivo zygotic ones, the later development was divergent. In zygotic pro-embryos, the starch grains were distributed in a polarized decreasing graduent from the suspensor to the embryo proper, and were served as temporary stores, ultimately displaced by oil and protein. In parthenogenetic proembryos, however, they often showed an unpolarized, centripetally distributed gradient and turned to be a long-term storage. This abnormal physiological status may have a relation to the underdevelopment of the parthenogenetie embryoids.