Iridoid glycoside uptake by Castilleja integra via root parasitism on Penstemon teucrioides

Abstract

Castilleja integra was seeded in a pot of mature Penstemon teucrioides and allowed to grow to blossom stage as a root parasite on Penstemon. Aucubin, which is the major iridoid of the P. teucrioides root but which is normally lacking from C. integra, was isolated from the above-ground parts of the parasitic C. integra. The major iridoid glycosides of P. teucrioides leaves were aucubin, isoscrophularioside (10- O-cinnamylaucubin) and trans-eurostoside (10- O-p-hydroxycinnamylaucubin). The two cinnamyl esters from the leaves of P. teucrioides were not found in C. integra. This is the first demonstration of iridoid glycoside transmission from a root host plant to a parasitic plant.