Phloem transport of antirrhinoside, an iridoid glycoside, in Asarina scandens (Scrophulariaceae)

Iridoid glycosides, terpene-derived compounds found in many plant families, protect the plant against generalist and nonadapted specialist insect herbivores, fungi, and bacteria. Antirrhinoside, a common iridoid glycoside in the tribe Antirrhineae (Scrophulariaceae), was rapidly labeled when mature leaves of Asarina scandens were exposed to (CO2)-C-14. Antirrhinoside was translocated in the phloem along with sucrose. Radiolabeled antirrhinoside appeared in the petiole of the labeled lear within 20 min of the beginning of the labeling period. Antirrhinoside was also found in phloem sap obtained by the EDTA method.