Question

Match the type of phloem cell to it's characteristics.

• A. Connected to sieves
• B. Perforated end walls
• C. Dense cytoplasm
• D. Sclerenchymatous

Answer 1

There are four types of phloem cells, sieve tubes, companion cells, phloem parenchyma and phloem fibres. Sieve tube elements are also long, tube-like structures, arranged longitudinally and are associated with the companion cells. Their end walls are perforated in a sieve-like manner to form the sieve plates. The companion cells are specialised parenchymatous cells, which are closely associated with sieve tube elements. The sieve tube elements and companion cells are connected by pit fields present between their common longitudinal walls. Phloem parenchyma is made up of elongated, tapering cylindrical cells which have dense cytoplasm and nucleus. The cell wall is composed of cellulose and has pits through which plasmodesmatal connections exist between the cells. Phloem fibres (bast fibres) are made up of sclerenchymatous cells.