Question

what is meant by lignin ? where is it present

Answer 1

Lignin is an organic substance belonging to a group of aromatic alcohols. It is naturally produced by certain plants (especially woody plants and certain algal species). It is found in the secondary cell walls of plantswhere it serves as a binder for cellulose fibers and provides stiffness to the cell walls. It was first described by the Swiss botanistAugustin Pyramus de Candolle in 1813. He first called it lignine from the Latin word lignum meaning wood.1 That is because it is present in wood primarily to provide structural support and protection against degradation by microorganisms. It fills the spaces in the cell wall particularly in xylem tracheids, vessel elements and sclereid cells. Since lignin is hydrophobic it assists in the efficient water transport across the vascular tissue. Ecologically, the importance of lignin is associated with the carbon cycle. It takes carbon from the atmosphere into the woody plant tissues and therefore acts as an important reserve of carbon in the form of humus as the plant tissue slowly decomposes. they are present in cell wall

Answer 2

Lignin is a constituent of the cell walls of almost all dry land plant cell walls. It is the second most abundant natural polymer in the world, surpassed only by cellulose. Of the polymers found in plant cell walls, lignin is the only one that is not composed of carbohydrate (sugar) monomers.
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