Lignin gymnospermous

In gymnosperms, the primary lignin precursors are the two monolignols coniferyl and /7-coumaryl alcohols, while in angiosperms sinapyl alcohol is also a participant in... 

The PAL activity that is necessary for lignin formation occurs in the cytoplasm or bound to the cytoplasmic surface of the endoplasmic reticulum membranes. The cinnamic acid produced is probably carried on the lipid surface of the membranes, since it is lipophilic, and it is sequentially hydroxylated by the membrane-bound hydroxylases (47,50). In this way there is the possibility of at least a two-step channeling route from phenylalanine to p-coumaric acid. The transmethylases then direct the methyl groups to the meta positions. There is a difference between the transmethylases from angiosperms and those from gymnosperms, since with the latter... 

In woody gymnosperms, there are significant differences in the distribution, reactivity and physical properties of protolignins found in the compound middle lamella and the secondary wall (1-3). Additionally, variations between lignins in vessels and fibers have also been noted (3). All of these... 

Already in 1897 Klason [52] suggested that gymnosperm lignin is derived from coniferyl alcohol. On the basis of experiments using isoeugenol as a model substance, Erdtman [53] advanced the hypothesis that lignin is a product of the oxidative polymerization of coniferyl alcohol ... 

Hatcher, P.G, and Minard, R.D. (1996) Comparison of dehydrogenase polymer (DHP) lignin with native lignin from gymnosperm wood by thermochemolysis using tetramethylammonium hydroxide (TMAH). Org. Geochem. 24, 593-600. 

Figure 1.- Structural model for a modem lignin from gymnosperm (modified from Adler, 34). The numbering convention is shown for a typical structural unit of lignin. Reproduced with permission from reference 34. Copyright 1990 Elsevier Science Ltd.—UK.

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