HORTICULTURE

Detailed explanation-1: -In addition to being a preformed, passive barrier limiting access of pathogens to plant cells, the cell wall is actively remodeled and reinforced specifically at discrete sites of interaction with potentially pathogenic microbes.

Detailed explanation-2: -The primary cell wall of land plants is composed of the polysaccharides cellulose, hemicelluloses and pectin. Often, other polymers such as lignin, suberin or cutin are anchored to or embedded in plant cell walls.

Detailed explanation-3: -Secondary cell walls contain additional components, such as lignin, which is hard and occupies the interstices between the other components, making the walls rigid and permanent.

Detailed explanation-4: -Cell membranes act as a barrier and gatekeeper between two distinct areas. Due to their semi-permeable nature, only a small number of molecules may penetrate the lipid bilayer. Gas and small hydrophobic molecules, such as oxygen and and carbon dioxide can quickly pass through membranes.