Apoplastic pH and Monolignol Addition Rate Effects on Lignin Formation and Cell Wall Degradability in Maize

• Published in: Journal of agricultural and food chemistry 2003-08, Vol.51 (17), p.4984-4989
• Main Authors: Grabber, John H, Hatfield, Ronald D, Ralph, John
• Format: Article
• Language: English
• Subjects: apoplast pH; biosynthesis; Cell Wall - chemistry; Cell Wall - metabolism; cell walls; chemical reactions; coniferyl alcohol; corn; crosslinking; dehydrogenation polymers; Hydrogen-Ion Concentration; Hydrolysis; lignification; lignin; Lignin - chemistry; Lignin - metabolism; phenols; polymerization; Polymers - chemistry; Zea mays; Zea mays - chemistry
• ISSN: 0021-8561; 1520-5118; 1520-5118
• DOI: 10.1021/jf030027c

Monolignol polymerization rate and apoplastic pH and may influence the formation of lignin and its interactions in cell walls. Primary maize walls were artificially lignified by gradual “end-wise” or rapid “bulk” polymerization of coniferyl alcohol at pH 4 or 5.5. Lignification efficiency was greatest for end-wise polymers at pH 5.5 (90−98%), intermediate for bulk polymers formed at either pH (54−82%), and lowest for end-wise polymers at pH 4 (41−53%). End-wise polymers had about 2.2-fold more ether inter-unit linkages and 70% fewer end-groups than bulk polymers. Low pH enhanced the formation of ether linkages in end-wise but not in bulk polymers. Differences in lignin structure did not influence the enzymatic degradability of cell walls, but lowering apoplastic pH from 5.5 to 4.0 during lignification reduced cell wall degradability by 25%. Further studies indicated this pH-dependent depression in degradability was related to cell wall cross-links formed via lignin quinone methide intermediates. Keywords: Zea mays; cell wall; apoplastic pH; Zulauf bulk polymers; Zutropf end-wise polymers; cross-linking; quinone methide intermediate; lignin-carbohydrate complex; thioacidolysis; enzymatic hydrolysis; degradability