Abstract: A recent advance in plant experimental embryology is the induction of haploid plants via in vitro culture of unfertilized ovules. Using float culture method on liquid media, we have raised haploid as well as diploid embryoids in sunflower cultivars by ovule culture. The present investigation was aimed to know the origin and developmental processes of these embryoids. Young flowers 1–4 days before anthesis were dissected and ovules were inoculated on N6 medium supplemented with 0.5–2 ppm MCPA and 6% sucrose. During culture period, samples were collected at intervals, fixed, stained and sectioned by paraffin method. Fifty one gynogenie embryoids of various sizes were observed among Ca. 2000 ovules. They were located at the micropylar end of the embryo sacs and proved to be originated from the unfertilized egg cells. At the early stages, they bore a strong resemblance to the zygotic proembryos in vivo, but after a considerable enlargement, they grew into globular, ovoid or elongated big bodies without polarized organ differentiation. Chromosome counts on some mitotic figures in these embyoids revealed their haploid nature. Embryoids were also produced from the endothelial tissue, which proliferated markedly after inoculation, especially at the chalazal parts, resulting in massive multilayered irregular folds and then degenerated. In some eases, cell divisions at one or several places led to embryoid or callus formation. The problems of how to regulate the growth of in vitro ovules in order to promote the gynogenic embryoids and inhibit the somatic embryoids or calli are left for future research.

Key words: Sunflower, Ovule culture, Embryoid, Haploid