The uptake and metabolism of H-3-benzylaminopurine in tobacco (Nicotiana tabacum L.) and cucumber (Cucumis sativus L.) explants

The uptake and metabolism of H-3-benzylaminopurine (H-3-BAP) were studied i n explanted stem pith and leaves of tobacco and in the hypocotyls and cotyl edons of cucumber. The explants were kept for 2, 5, 8 and 20 h on MS medium with 0.8 mg.l(-1) 2,4-D, 0.5 mg.l(-1) BAP and 13.2 mg.l(-1) aspartic acid (induction medium) with or without H-3-BAP and C-14-sucrose. The highest up take of H-3-BAP was observed in tobacco leaves and cucumber cotyledons. The major metabolite in both species was H-3-benzylaminopurine riboside (H-3-B APR). The highest level was found in explanted cucumber cotyledons after 20 h in culture, the lowest in explanted tobacco stem pith. Intensive 7-gluco sylation of H-3-BAP was observed in explanted tobacco leaves after 20 h in culture, where the levels of 7-glucoside of H-3-BAP and of free H-3-BAP wer e equal. To study the morphogenic effect of growth regulators (BAP and 2,4- D), the explants were subcultured after short-term induction (20 h) to MS m edium without any growth regulators. In most cases, incubation of 20 h on i nduction medium was sufficient to induce the respective morphogenesis. Cucu mber hypocotyl and tobacco stem pith explants formed a callus on their basa l end. Root formation was observed on explanted cucumber cotyledons and sho ot formation on tobacco leaves. Long-term culture (3 weeks) of tobacco leav es on induction medium led to the formation of callus and globules. The mic roscopic analysis of globules indicated the presence of meristematic and tr acheidal cells.