THE CATABOLISM OF BIOSYNTHETIC PRECURSORS BY HIGHER PLANTS

Abstract

The time courses of evolution of labelled carbon dioxide after feeding biosynthetic precursors to Tanacetum vulgäre L., Mentha pulegium L. and Artemisia annua L. are reported. Although extensive decarboxylation of mevalonate occurred in all three species, a maximum of 0.05 % of tracer from [2–¹⁴C]–MVA, and no detectable incorporation from [1–¹⁴C]–MVA, occurred into monoterpenes. Incorporation of tracer from mevalonate into monoterpenes is concluded to be direct rather than involving degradation to carbon dioxide and reincorporation of this as has been recently proposed.

[¹⁴C]–Geraniol and the [¹⁴C]–labelled C–5 precursors derived from [2–¹⁴C]–MVA are little degraded to carbon dioxide (< 3 %), but sodium [¹⁴C]–acetate and [¹⁴C]–3,3–dimethylacrylic acid are broken down to a greater extent.