In vitro culture of midrib expiants of Gerbera: Adventitious root formation and callus induction

Abstract

Factors affecting adventitious root formation and callus formation were studied in isolated midrib expiants of a red flowering Gerbera clone. Expiants were isolated in vitro from generative plants grown in a heated greenhouse. Root formation was optimal in segments, taken from 6–14 cm long young leaves, which had been cultivated in continuous darkness at 25Ж29Ð C. Root formation was strongly decreased by placing the expiants with basal ends down in the medium as compared with basal ends up. Macroelements did not play a very important role. Rooting occurred only when both a sugar and an auxin were present in the medium. IBA in the concentration 10 −5 g/ml gave the highest rooting percentage, the greatest number of roots, and the highest root dry weight. The addition of a cytokinin decreased rooting, enhanced callus formation, but never induced the formation of adventitious buds. Induction of callus formation by cytokinins was strongly promoted by the addition of an auxin, IBA being the most effective; the most effective cytokinins were BA ( SD 4901 ) and SD 8339.