AP BIOLOGY

Detailed explanation-1: -The phloem is a complex tissue and is formed typically by three cell types, the sieve elements, the parenchyma cells, and the sclerenchyma cells (Figure 2a–d).

Detailed explanation-2: -The phloem tissue consists of several types of cells, including sieve elements, companion cells, and phloem parenchyma cells.

Detailed explanation-3: -The companion cells are specialized parenchyma cells in the phloem tissues of the angiosperms. They are nucleated living cells with several ribosomes, plastids, and mitochondria. Their nuclei and nucleoli are relatively large (an indication of being metabolically active).

Detailed explanation-4: -Phloem is a permanent complex tissue consisting of sieve tubes, companion cells, phloem fibers, and phloem parenchyma.