Lignin content and composition may vary due to natural mutation in the genes involved in the lignin biosynthesis pathway,
such as observed for brown-midrib (bmr) mutant plants. Bmr mutants produce a lignin which differs to the lignin of normal
plants, this results in a red-brown colour which is seen in the mid vein of the leaves, mutant plants have significantly less lignin than normal plants (Oliver et al. 2005).