IN-VITRO PLANTLET REGENERATION FROM COTYLEDON, HYPOCOTYL AND ROOT EXPLANTS OF HYBRID SEED GERANIUM

In vitro plantlet regeneration systems for the seed geranium (Pelargon ium x hortorum Bailey) using cotyledon, hypocotyl and root explants we re optimized by studying the influence of seedling age, growth regulat ors and excision orientation on organogenesis. Indole-3-acetic acid co mbined with zeatin yielded the highest rate of shoot production on cot yledon explants (0.2-2 shoots per explant). More shoots were produced on explants cut from the most basal region of cotyledons from 2 to 4-d ay-old seedlings than from older seedlings or more distal cut sites. H ypocotyl explants produced the highest number of shoots, up to 40 shoo ts per explant, on indole-3-acetic acid (2.8-5.6 mM) + zeatin (4.6 mM) or thidiazuron (4.5 mM). Maximum shoot formation (0.3-1.4 shoots per explant) on root explants occurred when they were cultured on medium c ontaining zeatin. Regenerated shoots rooted best on a basal medium con taining no growth regulators. There were substantial differences among cultivars in shoot formation from each of the explant systems.