AP BIOLOGY

Detailed explanation-1: -The lignin adds compressive strength and stiffness to the plant cell wall and is believed to have played a role in the evolution of terrestrial plants by helping them withstand the compressive forces of gravity. Lignin also waterproofs the cell wall, facilitating the upward transport of water in xylem tissues.

Detailed explanation-2: -Lignin provides mechanical strength and resistance against pathogens, and makes the cell walls impermeable to water, thus enabling the transport of solutes via tracheids in the xylem tissue.

Detailed explanation-3: -As a complex phenolic polymer, lignin enhances plant cell wall rigidity, hydrophobic properties and promotes minerals transport through the vascular bundles in plant [13]. In addition, lignin is an important barrier that protects against pests and pathogens [14].

Detailed explanation-4: -Lignin is an alkyl-aromatic polymer found in the cell walls of terrestrial plants. Lignin provides structure and rigidity to plants, is a natural, highly effective barrier against microbial attack, and enables water and nutrient transport through plant tissues.

Detailed explanation-5: -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.