AP BIOLOGY

Detailed explanation-1: -Parenchyma cells are thin-walled, living cells, that are isodiametric in shape. They form major ground tissues in plants. Parenchyma cells are undifferentiated cells, which are highly adaptable and modified to perform various functions.

Detailed explanation-2: -The xylem has a thick cell wall which has the deposition of the water-impermeable substance (lignin) whereas the phloem has a thin cell wall and made up of cellulose. b. The cell of the xylem is small in comparison to the phloem cell.

Detailed explanation-3: -Tracheid cell walls are composed of a thin primary wall layer and a thick secondary wall. The individual tracheids adhere to one another by a thin middle lamella (ML), and this together with the two adjacent primary walls are often referred to as the compound middle lamella (CML) [8, 9].

Detailed explanation-4: -Fibres with the thickest cell walls are found close to the vascular elements, but cells adjacent to phloem remain relatively thin-walled (arrowhead).

Detailed explanation-5: -Xylem parenchyma cells are living and thin-walled, and their cell walls are made up of cellulose.