The cv Ringo Rose of hybrid seed geranium (Pelargonium x hortorum Bail
ey), previously shown to be recalcitrant in culture, produced somatic
embryos when cotyledonary explants were cultured on regeneration mediu
m containing thidiazuron (TDZ), forchlorfenuron (CPPU), or a combinati
on of indole-3-acetic acid and N-6-benzylaminopurine (IAA+BAP). Amendm
ent of the basal medium with TDZ (0.5 mu M) was the most effective tre
atment. Addition of amino acids to the medium promoted the growth of s
omatic embryos. Retention of the proximal region of the cotyledon was
crucial for regeneration, but the removal of the distal 1/3 to 1/2 cot
yledon had no significant effect on somatic embryogenesis. Cotyledonar
y explants formed somatic embryos in higher frequency and much earlier
than hypocotyl explants cultured on the same medium. The somatic embr
yos induced on cotyledonary explants were germinated on basal medium.
More than 70% of the somatic embryos were converted into plants and tr
ansferred to soil.