Aerial roots of two monopodial thick-leaved epiphytic orchids (A randa and Vanda) are a possible
source of endogenous plant hormones (abscisic acid, cytokinins, indole-3-acetic acid). Using a monoclonal
antibody-based immunoassay, this study also revealed that the levels of plant hormones in root
tips of Aranda could vary with root position along the stem, time and growth stages. The levels of plant
hormones are usually higher in root tips than elsewhere in the roots. Higher levels of cytokinin (mainly
isopentenyladenosine) were detected in root tips of flowering plants than in non-flowering plants of
Aranda. Lateral aerial roots(s) could be induced by the removal of root tip. A possible ro