P. Mosoni et al., C-14 LABELING OF LIGNINS OF NORMAL AND BM3 MAIZES FOR FERMENTATION STUDIES, Journal of the Science of Food and Agriculture, 64(2), 1994, pp. 145-154
[U-C-14] phenylalanine (phe) and [(OCH3)-C-14] sinapic acid (sin*) we
re infused into the cut ends of normal and bm3 maizes (anthesis stage)
under or above the last node or at mid-internode, with or without the
leaf, in light or in darkness. Radioactivity was measured in the orga
ns, and in phenolic constituents of the cell wall and saponified resid
ues of the bases and tops of the apical internode. In both maize genot
ype labelled under the node the radioactivity was distributed more eve
nly in the organs with sin than with phe*. Infusion above the node an
d at mid-internode greatly increased radioactivity in the bases and to
ps, respectively. Removal of the leaf only slightly increased the radi
oactivity, mainly in the bases, and no clear-cut effect of darkness wa
s observed. Phe labelled the phenolic acids and the three lignin unit
s, but the syringyl units of bm3 maize were only slightly labelled. Si
n specifically labelled the syringyl units, which represented the lea
st condensed fraction of lignins. Both the native and labelled lignins
were highly alkali soluble. There were differences in lignin biogenes
is between the bases and tops, and between normal and bm3 maizes. The
newly formed lignins were slightly different from the native lignins b
ut had similar types of heterogeneity, with variations in the internod
e and between genotypes similar to those in native lignins. Provided d
ue allowance is made for the distinguishing characteristics of newly f
ormed lignins, the [C-14-lignin] cell walls, which are strongly labell
ed on complementary structures, seem suitable model substrates for fer
mentation studies.