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United States Department of Agriculture

Agricultural Research Service

Title: The two "theories" of Lignification

Author
item Ralph, John

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 14, 2006
Publication Date: N/A

Technical Abstract: Lignification is the plant cell wall process by which lignin polymers are produced from phenolic monomers. These monomers are primarily the three hydroxycinnamyl (p-coumaryl, coniferyl and sinapyl) alcohols. Structural analysis of cell wall lignins and mechanistic studies of possible biosynthetic pathways have led to a general consensus among workers in the field that the polymer is a product of oxidative coupling of phenols. The theory of “combinatorial” coupling of phenoxy radicals formed from the monolignols under simple chemical control (based on original work by Freudenberg) continues to accommodate all the currently known facts of lignin chemistry. This state of affairs has been challenged in recent years without any basis in factual evidence. A new challenge-hypothesis has been unilaterally raised to theory status and the existing theory denigrated as an unsupported notion. We have examined the key arguments in the new hypothesis and find that those raised against the existing theory are invalid. Arguments for the new contender, advocating absolute proteinaceous control, are found to be convoluted, ambiguous, or reliant on misinterpreted data. The logical conclusion from examining the facts is that the new hypothesis fails to challenge the current theory.

Last Modified: 7/28/2014
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