Biological variability in lignification of maize: Expression of the brown midrib bm2 mutation

The cell wall phenolic components in the internodes of three maize genotypes, namely normal, bm2 and bm3 maize, were determined. The bm2 and bm3 brown midrib mutations lowered the lignin content of the bottom, middle and top internodes to a similar extent. However, unlike bm3, the bm2 trait did not induce a sharp reduction of the level of ester-bound p-coumaric acid in maize internodes. The other main alkali labile phenolic acid, ferulic acid, reached similar levels in the three genotypes. The main difference between bm2 and bm3 mutations occurred in the alkyl aryl ether linked structures of the lignin component. In contrast to bm3 lignins, which are characterised by a low syringyl content, the bm2 lignin had a lower content of guaiacyl units than lignin of normal maize internode. Consequently, the syringyl/guaiacyl molar ratio of bm2 lignin gave higher values (2.7–3.2) than those from either normal (0.9–1.5) or bm3 lignins (0.3). The alkali solubility of lignin was also compared between the three genotypes. Incorporation of the bm3 trait in maize led to a high recovery of alkali soluble lignin whereas the bm2 lignin had a similar solubility to the normal one in 2 M NaOH. The monomeric composition of the alkali soluble lignins was consistent with the non-condensed structures of the in-situ polymer. Although the bm3 and bm2 mutations had different effects on lignification, the modification of the cell wall phenolic level was also found in the bm2 maize stem as previously studied.     

Relationship of cell wall composition to in vitro cell wall digestibility of maize inbred line stems

The phenolic equipment of maize stem tissues was investigated in relation to the feeding value of the detergent fibre components. Sixteen maize inbred lines, including three brown‐midrib 3 mutants and their normal counterparts, were selected for highly divergent in vitro cell wall digestibility. These lines were grown during two years. Maize stems were analysed for detergent fibre concentration, esterified and etherified p‐hydroxycinnamic acids, lignin content and structure and in vitro digestibility. A large genotypic variation was found for neutral detergent fibre, cell wall phenolic composition and cell wall digestibility. Within the normal maize lines the in vitro neutral detergent fibre digestibility (IVNDFD) of stem fractions was negatively correlated with their Klason lignin content. A multiple regression model based on esterified p‐coumaric acid and lignin composition as two explanatory variates accounted for 58% of the IVNDFD variation. In this study, three normal maize inbred lines displaying a lignin content and a cell wall digestibility level close to those observed in the three bm3 lines could be detected, which opens up new breeding avenues. © 2000 Society of Chemical Industry     

Microbial degradation of normal maize and bm3 maize in the rumen observed by scanning electron microscopy

Samples of internodes and leaf blades from normal and bm3 maize (Zea mays L) harvested at dough to glazing stage were studied separately to determine their dry matter content, wall composition (NDF, ADF and ADL) and digestibility in sacco. For examination by light and scanning electron microscope, fragments 0·5 cm long were cut halfway along the internode beneath the female ear and on the corresponding blade. The wall and lignin contents of the bm3 maize were lower than in normal maize. The bm3 maize had a greater extent and faster rate of internode and blade disappearance in the rumen than normal maize samples. The histological structure of the two maizes was the same, but after 24 h in the rumen the parenchyma of the bm3 maize had degraded faster and the secondary walls of the fibres of its vascular bundles were degraded whereas those of normal maize had remained intact. After 72 h in the rumen the sclerenchyma of normal maize had changed little whereas that of the bm3 maize had much thinner walls and was abundantly colonised by rumen bacteria.     

Immunocytochemical localisation of para-coumaric acid and feruloyl-arabinose in the cell walls of maize stem

Two phenolic compounds, p-coumaric acid and feruloyl-arabinose, were localised by immunocytochemistry in the cell walls of the apical internode of two lines of maize (Co125 and W401) of different digestibility. The compounds were detected at two stages of cell maturity in the lignified tissues (sclerenchyma, fibres and xylem) and in the medullary parenchyma, which, in the samples studied, was not lignified. p-Coumaric acid is a phenolic acid associated with lignins, which confer resistance on plant cell walls to microbial degradation in the rumen. Feruloyl-arabinose is a compound associated with xylans, the principal hemicelluloses in Gramineae, which are potentially degradable. Labelling of p-coumaric acid decreased in both maize lines with cell age and as the cell walls became lignified. The mass of lignin deposited in the cell walls masked p-coumaric acid, thereby making it less accessible to the antibodies. There was an inverse relationship in the labelling of p-coumaric acid and feruloyl-arabinose. Feruloyl-arabinose was more heavily labelled as the plant cell walls matured in all the lignified tissues of both maize lines and in the parenchyma of the less digestible line. All tissues except the parenchyma were more heavily labelled with both sera in Co125, the more digestible line. © 1998 Society of Chemical Industry.     

Characterization of p‐coumarate accumulation,p‐coumaroyl transferase,and cell wall changes during the development of corn stems

BACKGROUND: Developmental changes occur in corn (Zea mays L.) stems from cell initiation to fully mature cell types. During cell wall maturation the lignin is acylated with p‐coumarates (pCA). This work describes characterization studies of the p‐coumaroylation process in relation to corn stem development. RESULTS: Corn plants from three locations were harvested and tissues were analyzed from all nodes and even‐numbered internodes above soil line. Changes in carbohydrates reflect a shift to lignification at the expense of structural polysaccharide synthesis. Accumulation of pCA paralleled the incorporation of lignin while ferulate (FA) remained relatively constant as a proportion of the cell wall (5–7 g kg^?1 CW). The p‐coumaroyl transferase (pCAT), which is responsible for attaching pCA to lignin monomers, displayed maximum levels of activity in the middle region of the stem (internodes 10–12, 2–3 nmol L^?1 min^?1 mg^?1). The syringyl content as a proportion of the total lignin did not change significantly with cell wall maturation although there was a trend towards increased amounts of syringyl units in the more mature cell walls. CONCLUSIONS: Incorporation of pCA into corn cell walls not only mirrored lignification but the pCAT activity as well. Levels of pCAT activity may be an indicator of rapid lignification specifically for syringyl type lignin. Copyright © 2008 Society of Chemical Industry     

Phenolic components and degradability of the cell walls of the brown midrib mutant,bm3, of Zea mays

Cell walls separated from the leaf blade, leaf sheath and stem of the brown midrib mutant, bm₃, of Zea mays were more degradable by a commercial cellulase than the corresponding part of the isogenic normal inbred cultivar (Tr). The walls of each part of the mutant when compared with the corresponding part of the normal cultivar contained less lignin and bound phenolic components released by treatment with NaOH. The major phenolic components detected were trans-p-coumaric and trans-ferulic acids together with small amounts of their cis isomers and diferulic acid. Cell walls of stem of the mutant contained a total of 17.3 mg g^?1 of these bound acids compared with 9.8 mg g^?1 for leaf sheath and 3.5 mg g^?1 for leaf blade: there was more than twice as much p-coumaric acid in cell walls of stem as in those of leaf sheath and more than seven times as much as in those of leaf blade. When cell walls of the stem from the mutant or the normal cultivar were treated with NaOH their degradability by cellulase was highly correlated with the amounts of phenolic components released by the alkali.     

Chemical and in vivo evaluation of a brown midrib mutant of Zea mays. I. Fibre, lignin and amino acid composition and digestibility for sheep

Two types of corn (maize) were used which were genetically identical except for a mutant gene (bm₁) in one which reduced the type and amount of lignin produced compared with the normal plant (Tr). The Tr plant appeared to have only slightly lower digestibilities of dry matter and fibre for sheep even though the protein contents of the cornstalks, normally less in the Tr, were equalised by supplementation with soya bean protein. Comparing the acid-detergent method of fibre and lignin determination with an acid-pepsin method revealed that the former method gave values considerably lower than the latter. The alkali—lignin contents of the bm₁ were higher than the acid—detergent lignins which must under-estimate the true lignin content. The acid—pepsin method gave fibre and lignin concentrations which were more closely correlated with rumen digestion of the diets as shown by dry matter loss of the diets suspended into the rumen in nylon bags. This technique also revealed there was a significant increase in the rate of rumen digestion after 69 to 74 h of incubation. Digestion of lignin on the Tr diet could be explained by loss of ferulic and p-coumaric acids. The reduced lignin and p-coumaric acid content of the bm corn was associated in young plants with a low phenylalanine content but normal tyrosine content suggesting that the genetic block in lignin synthesis in this plant may occur between prephenic acid and phenylalanine.     

Lignin composition is more important than content for maize stem cell wall degradation

BACKGROUND

The relationship between the chemical and molecular properties – in particular the (acid detergent) lignin (ADL) content and composition expressed as the ratio between syringyl and guaiacyl compounds (S:G ratio) – of maize stems and in vitro gas production was studied in order to determine which is more important in the degradability of maize stem cell walls in the rumen of ruminants. Different internodes from two contrasting maize cultivars (Ambrosini and Aastar) were harvested during the growing season.

RESULTS

The ADL content decreased with greater internode number within the stem, whereas the ADL content fluctuated during the season for both cultivars. The S:G ratio was lower in younger tissue (greater internode number or earlier harvest date) in both cultivars. For the gas produced between 3 and 20 h, representing the fermentation of cell walls in rumen fluid, a stronger correlation (R² = 0.80) was found with the S:G ratio than with the ADL content (R² = 0.68). The relationship between ADL content or S:G ratio and 72‐h gas production, representing total organic matter degradation, was weaker than that with gas produced between 3 and 20 h.

CONCLUSION

The S:G ratio plays a more dominant role than ADL content in maize stem cell wall degradation. © 2017 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Lignin and Hydroxycinnamic Acids in Walls of Brown Midrib Mutants of Sorghum,Pearl Millet and Maize Stems

The characteristics of walls from stems of brown-midrib ( bmr ) mutants from Sorghum bicolor (L) Moench bmr6 and bmr18 (watery- to milky-grain stage), Pennisetum americanum (L) Leeke KS81-1089 (soft-dough stage) and Zea mays L bm3 (early-dent stage) with respect to the types of linkages of hydroxycinnamic acids to wall polymers and to structural features of their lignins were investigated. The lignin content of all mutants, determined using the acid detergent lignin procedure, was significantly lower than that of their normal counterparts. There was, however, no significant differences in total lignin contents between bmr and normal lines as determined by the acetyl bromide procedure or the sum of the acid-insoluble (Klason) lignin and acid-soluble lignin. It is suggested that this behaviour could be explained if bmr mutants are characterised by higher amounts of lignin with a lower degree of polymerisation than normal lines. The lowered S/V ratio and lowered total yield of alkaline nitrobenzene oxidation products in lignin from bmr mutants was confirmed. No etherified p -coumaric acid was found in any sample tested, except the normal line of pearl millet. The concentration of etherified ferulic acid, which is probably involved in ester-ether bridges between lignin and polysaccharides, was lower in bmr mutants than in the normal plants. The low content of ferulic acid bridges in bmr mutants may contribute to the elevated digestibilities of their stems.     

14C labelling of lignins of normal and bm3 maizes for fermentation studies

[U-¹⁴C] phenylalanine (phe*) and [O¹⁴CH₃] sinapic acid (sin*) were 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 organs, and in phenolic constituents of the cell wall and saponified residues of the bases and tops of the apical inter-node. In both maize genotype labelled under the node the radioactivity was distributed more evenly in the organs with sin* than with phe*. Infusion above the node and at mid-internode greatly increased radioactivity in the bases and tops, respectively. Removal of the leaf only slightly increased the radioactivity, mainly in the bases, and no clear-cut effect of darkness was observed. Phe* labelled the phenolic acids and the three lignin units, but the syringyl units of bm3 maize were only slightly labelled. Sin* specifically labelled the syringyl units, which represented the least condensed fraction of lignins. Both the native and labelled lignins were highly alkali soluble. There were differences in lignin biogenesis between the bases and tops, and between normal and bm3 maizes. The newly formed lignins were slightly different from the native lignins but had similar types of heterogeneity, with variations in the internode and between genotypes similar to those in native lignins. Provided due allowance is made for the distinguishing characteristics of newly formed lignins, the [¹⁴C-lignin] cell walls, which are strongly labelled on complementary structures, seem suitable model substrates for fermentation studies.     

Characterisation of Lignin from Parenchyma and Sclerenchyma Cell Walls of the Maize Internode

Internodes of maize (Zea mays L, Co125), harvested 5 days after anthesis, were sectioned into five equal parts and samples of sclerenchyma and parenchyma cells mechanically isolated from each section. Phenolic acids and syringyl and guaiacyl degradation products of lignin were released from the walls of the two cell types by microwave digestion with 4 M NaOH. Aryl ether bonded units were selectively released by thioacidolysis. Total phenolic content of cell walls from the youngest (basal) sections were approximately two-thirds of those of the oldest, topmost sections (parenchyma 70·8–99·0 and sclerenchyma 72·5–114·1 mg g^-1) indicating that the process of lignification was already well advanced amongst most of the cell walls of the youngest section. The total phenolic content was marginally, but significantly, greater (P<0·05) in sclerenchyma walls than in parenchyma walls at all stages of maturity. There was no significant difference in phenolic acid concentrations between cell types from the same section but p-coumaric acid concentration increased with maturity (P<0·001) in walls from both cell types. The increase in p-coumarate with age was matched by an increased recovery of syringyl units resulting in a constant coumaroyl: syringyl molar ratio. Recovery of acetosyringone was significantly greater (P<0·001) from sclerenchyma than parenchyma walls and, in sclerenchyma, acetosyringone as a proportion of total syringyl recovery, increased significantly with age (P=0·015). Digestion with NaOH and thioacidolysis released comparable amounts of guaiacyl residues but NaOH digestion released approximately twice the amount of syringyl residues. This difference may be explained by the retention of the ester-bond between p-coumaric acid and syringyl units during thioacidolysis but not during digestion with 4 M alkali. The similarity in phenolic composition suggested that both cell types, despite their considerable anatomical differences, were exposed to a common flux of lignin precursors during the later stages of lignification as illustrated by the internode sections. Differences between cell walls arose because of differences in the regiochemistry of precursor incorporation. © 1997 SCI.     

Higher intake of DK265 corn silage by dairy cattle

In this experiment, intake of DK265 3-way corn hybrid by dairy cattle was compared specifically with intake 1) of its bm3 isogenic form, 2) of its 2 related single-way hybrids, and 3) of 2 controls that were registered hybrids of similar earliness. Both dry matter (DM) and lignin contents were similar in all hybrids except for the bm3 hybrid, which was less lignified. There was a tendency for lower starch content and, correlatively, higher neutral detergent fiber content in DK265 and in the 2 related single-way hybrids. Significant intake differences were observed between hybrids; the highest intake was recorded for the bm3 hybrid. Among normal hybrids, DK265 and one of its related single-way hybrids registered significantly higher intakes than other hybrids. Among normal hybrids, cell wall digestibility and/or lignin content did not explain all of the variations observed for intake, whereas the higher intake of DK265 bm3 could be related to its lower lignin content as compared with isogenic DK265. It was hypothesized that the higher intake observed for the DK265 hybrid was probably related to specific friability traits that are not relevantly measured through the usual tests used in corn breeding.     

Transformations of (14C-lignin) cell walls of wheat by rumen microorganisms

The lower halves of apical internodes of wheat harvested at the flowering stage were labelled with [U-¹⁴C] phenylalanine (phe) or with [O¹⁴CH₃] sinapic acid (sin). Cell wall residues (CWR) and saponified residues (SR) were incubated in a fermenter simulating the rumen for 7 days with rumen fluid or without microorganisms (controls). PheCWR was labelled in all lignin units (measured as aldehydes from nitrobenzene oxidation), in phenolic acids and slightly in proteins. Labelling of pheSR was more lignin-specific. SinCWR and sinSR were specifically labelled in syringyl units of lignin. The fermentation of CWR resulted in phenylpropane-derived unit losses in the following decreasing order: ferulic acid>p-coumaric acid>syringaldehyde>vanillin>p-hydroxybenzaldehyde. If allowance is made for slight losses in controls, 61, 52, 61 and 63% of the phenylpropanes of pheCWR, sinCWR, pheSR and sinSR, respectively, were transformed into an acid-precipitable fraction, an acid-soluble fraction and ¹⁴CO_2. The comparison of pheCWR and sinCWR degradation showed that syringyl units were solubilised into acid-precipitable molecules to a greater extent than the other lignin units; demethylation of the syringyl units of lignins was also evident from the different productions of ¹⁴CO₂. Alkali-resistant lignins of SR were mainly transformed into acid-precipitable molecules and were weakly degraded. Lignin solubilisation and degradation seem to be governed by different mechanisms which depend on both cell wall structure and rumen microflora.     

Impact of lignin composition on cell‐wall degradability in an Arabidopsis mutant

An Arabidopsis mutant that does not deposit syringyl‐type lignin was used to test the hypothesis that lignin composition impacts cell‐wall degradability. Two lines of the ferulate‐5‐hydroxylase‐deficient fah1 mutant and the wild‐type control line were grown in the greenhouse. In Experiment 1, the plants were harvested at the mature seed stage. For Experiment 2, plants were harvested 5, 6, 7 and 8 weeks after sowing. In both experiments stems were collected and analysed for cell‐wall concentration and composition, and in vitro degradability of cell‐wall polysaccharide components by rumen micro‐organisms. The absence of syringyl‐type lignin was confirmed for the mutant lines by nitrobenzene oxidation and pyrolysis‐GC‐MS. Lignin concentration was the same for all three Arabidopsis lines, at all stages of maturity. The Arabidopsis stems were similar to forage legumes in that the potentially degradable cell‐wall fraction was very quickly degraded. Cell‐wall polysaccharide degradability did not differ among the Arabidopsis lines in the first experiment after 24‐h fermentations, but the cell‐wall polysaccharides of the fah1‐2 mutant line were less degradable after 96‐h than either the wild‐type or the fah1‐5 mutant. In contrast, in Experiment 2 no differences among lines were found for cell‐wall polysaccharide degradability after either 24‐ or 96‐h fermentations; however, signficantly higher levels of ester‐bound ferulic acid were found in the walls of the fah1 mutant lines. As expected, increasing stem maturity was correlated with reduced degradation of cell‐wall polysaccharides. These experiments indicate that either lignin composition, as measured by syringyl‐to‐guaiacyl ratio, does not alter cell‐wall degradability in Arabidopsis, or that the fah1 mutation has other effects on the cell walls of these mutants such that the impact of the change in syringyl‐to‐guaiacyl ratio is masked. © 1999 Society of Chemical Industry     

Forage quality variation among maize inbreds: Relationships of cell-wall composition and in-vitro degradability for stem internodes

Forty-five inbred maize (Zea mays L) lines were evaluated for genetic variation in stem cell-wall concentration, composition and degradability, and for relationships among cell-wall components and polysaccharide degradability. Cell-wall neutral sugars, uronic acids, Klason lignin, and ester- and ether-linked phenolic acids were measured on lower stem internode samples collected at the time of silking in 2 years. Twenty-four and 96 h in-vitro ruminal fermentations were used to determine the rapidly and potentially degradable cell-wall polysaccharide fractions, respectively. Genetic variation (P < 0.05) was found for all measures of cell-wall composition and many estimates of rapidly and potentially degradable cell-wall polysaccharide components. Inbred line means varied by 50–300% for most traits. Three brown midrib mutant inbred lines included in the study were not the lowest in lignin content nor did they exhibit the greatest cell-wall degradabilities in this population of inbred maize. Year of growth (environment) influenced (P < 0.05) cell-wall traits even though reproductive physiological maturity at sampling was similar in both years. Degradability of the cell-wall polysaccharide components were intercorrelated (P < 0.05) within the rapidly and potentially degradable fractions, but rate and extent of degradation of the cell-wall components were not correlated (P > 0.05), except for uronic acids. A multiple regression model of principal components (R² = 0.41, P < 0.05) indicated that cell-wall lignification and substitution of wall polymers with phenolic and uronic acids were negatively associated, and pectic substances were positively related with rapid polysaccharide degradation. Very little of the variation (R² = 0.15, P < 0.05) in potential cell-wall polysaccharide degradation could be explained by this multiple regression analysis. There is a large degree of genetic variation among current inbred maize lines for stem cell-wall quality traits, which should allow improvement of maize as a forage crop. Because of the complex matrix interactions in cell-wall organization, however, no single cell-wall component, or simple combination, can accurately predict degradability of maize cell walls.     

Solid-state 13C NMR study of palm trunk cell walls

Trunk material from the oil palm Elaeis guineensis was dissected into parenchyma and vascular bundle fractions, which were individually examined by ¹³C solid-state nuclear magnetic resonance at low field (25 MHz). Cross-polarisation and magic-angle spinning were used with dipolar dephasing to reveal the aromatic carbons of lignin free from interference by carbohydrate. The lignin contents of the parenchyma and vascular bundles were found to be 240 g kg^?1 and 130 g kg^?1, respectively. The lignin appeared to contain a high proportion of aryl ether-linked syringyl units, but little or no ferulic or p-coumaric acid. The cellulose of both fractions had a high proportion of the crystalline component. The acetyl content was c 6 mol %C. The in-vitro digestibility of the two fractions was measured using the rumen liquor-pepsin method and was found to be low compared with forage materials: 19.5% in the parenchyma and only 11.1% in the vascular bundles.     

The newly extended maize internode: A model for the study of secondary cell wall formation and consequences for digestibility

The upper five internodes were collected from maize (Zea mays L) inbred cell lines Co 125 and W401 harvested at the same developmental stage, 5 days after silking. Each internode was dissected into ten equal lengths labelled A (top) to J (base). The youngest cells were found in section J, which contained the intercalary meristem, and the oldest in section A. Internodes 1, 3 and 5 provided material for chemical analysis and internodes 2 and 4 for degradability measurements. Cell wall material accounted for one-third of dry matter in section J, doubling to two-thirds in the upper half of each internode. Only section J exhibited a polysaccharide profile typical of primary cell walls. In all other sections, 1,4-linked glucose (± 46% of cell wall) and xylan largely free from side chains (± 25% of cell wall) predominated. Net accretion of cell wall polysaccharide reached a maximum by segment G and thereafter little additional carbohydrate was deposited. Lignification appeared to be separated from the biogenesis of structural carbohydrate and continued over much of each internode reaching a maximum in section C. Degradability measurements, made using a modified neutral-detergent cellulase digestibility method, showed substantial differences between sections. In line Co 125, cell wall degradability fell from over 95% in the youngest section (J) to approximately 24% in section B. Internode 4 of line W401 failed to show the same pattern of degradabilities, probably because of a sequential rather than simultaneous pattern of internode elongation. Saponifiable p-coumaric acid appeared to provide a more sensitive marker than lignin of the extent of secondary wall development. The inverse relationship between extent of lignification in each section and its degradability confirmed the value of the internode model for the study of secondary wall formation and its biological consequences.     

烟草木质素结构的二维核磁共振波谱表征

[背景和目的]烟草木质素对烟草品质和安全性有重要影响,为了提高烟草制品的质量,需要探究烟草木质素的化学结构及含量.[方法]利用二维异核单量子相干核磁共振技术(2D HSQC NMR)建立表征烟草木质素的方法,实现烟草木质素的结构表征及半定量分析.[结果](1)烟草样品木质素中共发现10种主要的木质素基本单元及单元间连接...     

Effect of storage period on provitamin-A carotenoids retention in biofortified maize hybrids

Vitamin A-rich maize hybrids provide sustainable solutions to malnutrition. However, significant loss of carotenoids during storage reduces its efficacy. Grains of nine sub-tropically adapted crtRB1-based biofortified hybrids along with six normal hybrids were stored under conventional storage for five months. PVAC (β-carotene and β-cryptoxanthin) among crtRB1-based hybrids degraded from initial level of 18.77 to 3.24 µg g⁻¹, while NPVAC (lutein and zeaxanthin) reduced to 10.79 µg g⁻¹ from 19.00 µg g⁻¹ during storage. Among PVAC, β-cryptoxanthin (21.8%) possessed more stability than β-carotene (16.4%). For NPVAC, lutein (61.2%) showed the highest retention than zeaxanthin (50.4%). Majority of the PVAC loss occurred within first three months of storage. Retention for PVAC among crtRB1-based hybrids varied from 14% to 23% indicating the role of favourable genetic factors. APQH1, APQH7 and APH2 were the promising hybrids with higher retention (>20%) of PVAC. This is the first report on identification of provitamin A-rich crtRB1-based biofortified maize hybrids with higher retention during sub-tropical storage.     

Cell wall composition and degradability of forage stems following chemical and biological delignification

Chemical and biological delignification methods were used to investigate the relationship between the concentration and composition of lignin and degradation of forage cell walls. Stem material from lucerne (Medicago sativa L), smooth bromegrass (Bromus inermis Leyss) and maize (Zea mays L) stalks was treated with alkaline hydrogen peroxide, potassium permanganate, sodium chlorite, sodium hydroxide, nitrobenzene, and the lignolytic fungus Phanerochaete chrysosporium. Klason lignin and esterified and etherified phenolic acids were delermined. Cell wall neutral sugar and uronic acid composition and the extent of in-vitro degradability were measured. Chemical delignification generally removed lignin. but the fungal treatment resulted in the removal of more polysaccharide than lignin. The concentrations of esterfied and etherified p-coumaric and ferulic acids were generally reduced in treated cell walls; chlorite treatment preferentially removing p-coumaric acid whereas nitrobenzene treatment removed more ferulic acid. Syringyl moieties were completely removed from the core lignin polymer by nitrobenzene treatment of forage stems. Alkaline hydrogen peroxide and nitrobenzene were generally the most effective delignification treatments for improving polysaccharide degradability, with the grass species responding similarly to delignification whereas lucerne was somewhat less responsive. Fungal delignification, under these experimental conditions, did not improve cell wall degradability of these forages. Multiple regression and covariate analyses indicated that the lignin components measured were not powerful predictors of cell wall degradability. Neither the concentration nor the composition of the lignin fractions was consistently correlated with degradation. This lack of effect was attributed to the more generalised disruption of the cell wall matrix structure by delignification treatments.