Tissue-specific developmental changes in cell-wall ferulate and dehydrodiferulates in sugar beet.

Sugar beet (Beta valgaris L.) seedlings were grown for 8-14 weeks, and then separated into leaf, petiole, inner and outer storage root and absorptive root fractions. Cell-wall ferulate and dehydrodiferulate esters were analysed by HPLC. In leaves, ferulate dimers were mostly 8-8 linked, while 8-O-4 and sometimes 8-5 linkages were most abundant in all other tissues. The total dimer content and percentage of dimerisation were much higher in the absorptive root than in other tissues. These results indicated varying patterns of ferulate and dehydrodiferulate ester content in different tissues, suggesting corresponding variations in the biosynthetic processes. When [14C]-cinnamate was applied to the leaves at 4 weeks, and [14C]-dimers measured in root cell walls at 8 and 14 weeks, a much higher proportion of 8-5 linkages was found in the [14C]-dimers than in total (non-radioactive) dimers in all parts of the root, especially at 14 weeks, indicating further complexity in the metabolism of cell-wall phenolics.