Somatic embryogenesis in the nickel hyperaccumulating shrub, Hybanthus floribundus (Lindl.) F. Muell

This study examines the role of cytokinins and auxins in somatic embryogenesis of the West Australian nickel hyperaccumulating shrub, Hybanthus floribundus. Nodal segments from micropropagated shoots were inoculated on to callus induction media consisting of basic MS medium supplemented with auxins (2,4-D, dicamba or picloram at 0, 1 or 5 μM), cytokinins (zeatin or Kn at 0, 0.1, 0.5 or 1.0 μM) or combinations of both auxins and cytokinins. Four weeks after culturing calli were observed. Callus pieces were subcultured on to fresh MS medium without any plant growth regulators. Explants produced both calli and shoots in all combinations of cytokinins and auxins. Development of somatic embryos was moderate and highly dependent upon the type and concentration of plant growth regulators used. Kinetin was more effective than zeatin. Kn produced somatic embryos either with or in absence of any of the auxins. Its effective concentration was 1 μM. Anatomical investigations have confirmed somatic embryogenesis in H. floribundus.