Source Year: 1996

Incorporation of 14C-labelled CO2, 3-phosphoglycerate (PGA), phosphoenolpyruvate (PEP) and pyruvate into hexane-extractable rubber fractions in cut shoots of guayule cv. 11591 was determined in order to evaluate the role of photosynthesis in providing precursors for rubber biosynthesis. DCMU inhibited the incorporation of labelled CO2 and PGA into rubber. The incorporation of 14CO2 increased with increasing light intensity. Enzymatic activities of phosphoglyceromutase, enolase, pyruvate kinase and pyruvate dehydrogenase complex in purified chloroplasts from the leaves indicated the chloroplast autonomy for intraplastid acetyl coenzyme A formation. Enzymes related to the biosynthesis of isopentenyl pyrophosphate (IPP) were associated with both leaf and stem extracts. Rubber-producing enzyme activities, namely IPP isomerase and rubber transferase, were abundantly localized in roots and stems of guayule, while the leaves exhibited low activities of these enzymes. Hence the leaves of guayule play a major role in providing precursors for rubber formation in stems and roots.