ISATIN AS AN AUXIN SOURCE FAVORING FLORAL AND VEGETATIVE SHOOT REGENERATION FROM CALLI PRODUCED BY THIN-LAYER EXPLANTS OF TOMATO PEDICEL

Thin layer explants taken from the pedicels and peduncles of flowering tomato plants yielded calli with great organogenetic potential. Of th e 15 cultivars tested, 7 regenerated roots, shoots and eventually enti re fruit-bearing plants. Calli grown on modified Murashige-Skoog mediu m responded to varied auxins and cytokinins with different morphogenet ic patterns. Thus, naphthaleneacetic acid yielded root-producing calli , while the auxin precursor isatin (indole 2,3-dione) caused the produ ction of calli with vegetative and floral shoots, rarely yielding root s. This may be related to isatin's slow, steady conversion to an activ e auxin (Plant Physiol 41:1485-1488, 1966) in contrast with naphthalen eacetic acid's immediate presentation of a high level of active auxin. The highest incidence of vegetative shoot (100%) and flower (50%) for mation was obtained with 10 mu M isatin and 3 mu M zeatin. A few of th e flowers developed into ripe fruits. The high frequency of induction of vegetative shoots and flowers before roots with isatin suggests its utility in micropropagation from plant tissue cultures.