AP BIOLOGY

Detailed explanation-1: -Collenchyma is a supporting tissue composed of more or less elongated living cells with unevenly thickened, nonlignified primary walls. It is in regions of primary growth in stems and leaves.

Detailed explanation-2: -Collenchyma, like parenchyma, lack secondary cell walls but have thicker primary cells walls than parenchyma. They are long and thin cells that retain the ability to stretch and elongate; this feature helps them provide structural support in growing regions of the shoot system.

Detailed explanation-3: -Collenchyma tissue possesses elongated cells with irregular thickening, mainly at the corners. They possess only thick primary cell wall made of cellulose and pectin.

Detailed explanation-4: -Sclerenchyma tissue (Figure 5) is composed of sclerenchyma cells, which are usually dead at maturity (i.e., have lost their protoplasts). They characteristically contain very thick, hard secondary walls lined with lignin; consequently, sclerenchyma provides additional support and strength to the plant body.

Detailed explanation-5: -Xylem cells commonly have cell walls impregnated with lignin and reinforced with spiral or ring-like thickenings that project into the lumen of the cell (Figure 1.2). Both features reinforce the cells for mechanical support. Figure 1.1: Xylem cell types.