UPTAKE AND TRANSPORT OF QUINOLIZIDINE ALKALOIDS IN CUSCUTA-REFLEXA PARASITIZING ON LUPINUS-ANGUSTIFOLIUS

During parasitism on Lupinus angustifolius the phanerogamic parasite Cuscuta reflexa takes up quinolizidine alkaloids from L. angustifolius via haustoria that tap xylem and phloem vessels of the host. The alkaloid pattern of the haustorial region of C. reflexa as revealed by GLC as well as by GLC-MS closely resembles that of infested lupin stems. With increasing distance from the haustoria towards the apex of C. reflexa the complex alkaloid pattern of the host is significantly reduced. Whereas alkaloid esters such as 13-benzoyloxylupanine and 13-cinnamoyloxy-lupanine are prominent peaks in the alkaloid profiles of the host as well as of the haustorial region of the parasite they are not detected in the apex of C. reflexa but are replaced by their respective alcohol component 13-hydroxylupanine. This change of alkaloid profiles is accompanied by a strong decline of alkaloid concentration which drops from approximately 11 mg/g dry wt. in the haustorial region of C. reflexa to 0.2 mg/g dry wt. in the apex. Alkaloid analyses of xylem sap and phloem exudate from L. angustifolius suggest that uptake of host plant alkaloids by C. reflexa is mainly via the phloem even though a contribution of xylem sap to the supply of alkaloids to the parasite can not be excluded.