Synthesis, transport and accumulation of quinolizidine alkaloids in Lupinus albus L. and L. angustifolius L.

ABSTRACT

Each of the principal quinolizidine alkaloids (QA) found in both xylem and phloem exudates together with extracts from all component organs collected from bitter (cv. Lupini) and sweet (cv. Ultra) cultivars of Lupinus albus L. were quantified by gas chromatographic analyses throughout reproductive development. In addition to establishing the major translocated QA species estimates for fluxes of QA to developing fruits based on their sap composition and water economy showed that around half of the QA that accumulated in fruit tissues was due to synthesis in situ and half to translocation principally by phloem. Detailed analyses of QA in transport fluids and component organs were extended to reciprocal homo- and hetero-grafts using bitter (cv. Fest) and sweet (cv. Danja) cultivars of L. angustifolius L. These data confirmed that the majority of QA were synthesized in shoot tissues. In both lupin species feeding and analysis of deuterated QA (lupanine and 13-hydroxylupanine) were used as tracers to demonstrate direct redistribution of alkaloids by translocation from mature leaves in phloem.