Propagation through stem cutting and air layering of a Critically Endangered tree <Humboldtia unijuga> Bedd. var. <trijuga> J.Joseph & V.Chandras. (Magnoliopsida: Fabales: Fabaceae)

Humboldtia unijuga var. trijuga is an evergreen tree, endemic to the southern Western Ghats of India belonging to the family Fabaceae, and is categorized as ‘Critically Endangered’. High rates of flower & fruit predation and the recalcitrant nature of seeds have detrimental effect on regeneration, and individual recruitment in the wild. Therefore, the present study aimed to produce saplings through conventional propagation methods of stem cuttings and air layering by exogenous application of auxins, with various concentrations of Indole-3-butyric acid (IBA), Indole-3 acetic acid (IAA), and α-Naphthalene acetic acid (NAA). The study revealed that both IBA and IAA had developmental effects on stem cuttings and air layering, but maximum rooting was observed at 1,500 mg/l of IBA. This concentration may be used for mass multiplication and conservation of this endangered tree species.