Tissue distribution and biosynthesis of 1,2-saturated pyrrolizidine alkaloids in Phalaenopsis hybrids (Orchidaceae)

The tissue distribution of phalaenopsine in the orchid plant suggests chemoecological importance of the alkaloids. In rosette plants the aerial roots are the sites of alkaloid biosynthesis. Phalaenopsine does not underlie degradation or turnover but is translocated to other plant parts. The results are discussed in the context of molecular evolution of pyrrolizidine alkaloid biosynthesis in angiosperms and ecological function of 1,2-saturated pyrrolizidine alkaloids.