EFFECT OF POLYETHYLENE-GLYCOL ON ADVENTIT IOUS BUD FORMATION ON HYPOCOTYL SEGMENTS OF TOMATO SEEDLING

The effect of polyethylene glycol (PEG) on adventitious bud formation on excised hypocotyl segments of tomato seedling cv. KNVF-R, an inters pecific hybrid rootstock between Lycopersicon esculentum x L. hirsutum , was investigated. 1. Segments excised from hypocotyls shorter than 8 cm and incubated under light intensity exceeding 3 klx formed buds; t he optimum segment length was 4 mm. About 95% of the segments formed a dventitious buds in 1/2 strength Murashige-Skoog basal medium suppleme nted with 50 g . liter-1 PEG-6000 and 30 g . liter-1 sucrose. However, when the number of segments per flask (containing 40 ml of medium) ex ceeded 50, the percentage of segments which initiated buds decreased. 2. Mannitol and PEG-1500 were not effective at all. Abscisic acid (ABA ) at 10 mg . liter-1 stimulated bud formation. 3. Segments with buds o f 2 mm length rooted within 2 weeks on a basal medium (1/2 MS suppleme nted with 30 g . liter-1 sucrose and 8 g . liter-1 agar) All regenerat ed plants were established by transplanting to a vermiculite potting m ixture.