MORPHOREGULATORY ROLE OF THIDIAZURON - MORPHOGENESIS OF ROOT OUTGROWTHS IN THIDIAZURON-TREATED GERANIUM (PELARGONIUM X HORTORUM BAILEY)

Root outgrowths formed on the root tissue of geranium (Pelargonium x h ortorum Bailey cv. Kim and cv. Shone Helena) plants in response to tre atment with the phenylurea derivative, thidiazuron (N-phenyl-N'-1,2,3- thiadiazol-5'-ylurea; TDZ). Treatment with the cytokinin N-6-benzylami nopurine (BAP) or the auxin alpha-naphthaleneacetic acid (NAA) did not result in stimulation of similar abnormal structures on the root tiss ue. Significantly more outgrowths developed on roots of plants treated with 10 mu M and 20 mu M TDZ than on control plants or those treated with 1 mu M TDZ for the eight-week treatment period. Some outgrowths p roduced shoots and plantlets while still attached to roots, and regene rants were easily separated from the root tissue and transferred to so il in the greenhouse where they grew to maturity. Histological observa tions suggested these outgrowths originated from the vascular cambium region of the root.