AP BIOLOGY

Detailed explanation-1: -The inner walls of the xylem vessels are strengthened by the deposits of a substance called Lignin.

Detailed explanation-2: -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-3: -The walls of xylem cells are lignified (strengthened with a substance called lignin ). This allows the xylem to withstand pressure changes as water moves through the plant.

Detailed explanation-4: -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-5: -Lignin (Latin lignum ‘wood’) is a polyphenolic polymer deposited directly in the cell wall of specialized cells. It is not only restricted to plant woody tissues but represents an integral feature ensuring the proper cellular function of many other cell types in different tissues/organs of the plant.