Abstract: In recent years haploid sunflower embryoids were induced in our lab by culture of unfertilized ovules[6] and these were revealed to be originated from the egg cells, i.e. via in Vitro parthenogenesis[5] 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 inositol. Samples were fixed at intervals in aceto-methanol (1:3) and processed by paraffin method. In Vivo 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 polysaceharide (Plate Ⅱ, 19–24). The nearly matured egg cells were characterized by negative Feulgen reaction of the nucleus, negative pyronin staining of the nueleolus, abundant pyroninophylic granules in the cytoplasm, rich cytoplasmic protein, but with- out starch grains. After fertilization, or when parthenogenesis was triggered, the cells of the early proembryo maintained weak Feulgen stain and pyroninophylic 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 longterm storage. This abnormal physiological status may have a relation to the underdevelopment of the parthenogenetic embryoids.

Key words: Sunflower, Ovule culture, Parthenogenesis(histochemistry) Projects Supported by the Science Fund of the Chinese Academy of Sciences.