M. Goto et al., VARIATIONS IN ANATOMY AND ULTRAVIOLET MICROSPECTROMETRY BETWEEN NORMAL AND BROWN MIDRIB MUTANT MAIZES POSSESSING DIFFERENT RUMEN DEGRADABILITIES, Journal of the Science of Food and Agriculture, 63(4), 1993, pp. 427-434
Normal and brown midrib mutant (bmr) maize (Zea mays L) were examined
for variations in their morphological composition. The degradability o
f the leaf blade, leaf sheath and stem, proportional area of specific
tissues in leaf blade, and the ultraviolet (UV) absorption spectra of
cell walls were measured and related to variations in cell wall degrad
ability by rumen microorganisms. The UV and infrared (IR) absorption s
pectra of the lignins isolated from leaf blades of both types, before
and after reduction with sodium borohydride, were recorded. The bmr3 m
aize had higher dry matter (DM) and neutral detergent fibre (NDF) degr
adabilities for leaf blade, leaf sheath, and stem than the normal coun
terpart. Approximately 35 % and 26 % of the observed difference in DM
degradability was attributed to the difference in DM degradability of
stem and leaf blade, respectively, and 39 % to the difference in DM co
mposition of stem. Distinct differences in tissue degradation of the l
eaf blades were observed for mesophyll cell walls in the midrib portio
n, which were thinner and of greater number in the bmr3 maize. Scleren
chyma cells were present only in the vascular bundles in the bmr3 leaf
blade, while in the normal type those cells were underneath the epide
rmis tissue. The bmr3 plant also had large epidermal cells. UV microsp
ectrometry of mesophyll cell walls of the bmr3 maize showed their lowe
r UV absorbance around 320 run compared to that of the normal, but not
at 280 nm. Considerable increase in the UV absorbance at 280 nm was o
bserved for the isolated lignins after reduction, suggesting a lesser
degree of lignification in the bmr3 maize tissues. Lowered UV absorban
ce of the isolated lignin around 320 nm after reduction was associated
with the removal of the IR bands at 1730, 1660, 1600, and 1250 cm-1.