Question

what is the relation between sieve tubes and companion cells?

Answer 1

Phloem:

1. It is a complex tissue in the vascular system of higher plants that consists mainly of sieve tubes and elongated parenchyma cells usually with fibers and that functions in translocation and in support and storage.
2. Sieve tubes and companion cells are the elements of phloem.

Sieve tubes:

1. The conducting element of the phloem is the sieve tube.
2. A vertical series of elongated cells form sieve tubes.
3. These tubes are interconnected by perforations in their walls in areas that are called sieve plates.
4. There can be restrictions on perforations to smaller areas.

Companion cells:

1. Specialized parenchyma cells in the phloem tissues of the angiosperms are companion cells.
2. They have quite large nuclei and nucleoli.
3. These living cells carry nuclei, ribosomes, plastids, and mitochondria.
4. Phloem consists of cells called sieve-tube elements.
5. Perforations are called sieve tube plates allow the traveling of phloem sap whereas the metabolic functions of the same sieve tubes are carried out by neighboring companion cells.
6. The companion cells are formed by connecting lateral sieve areas with sieve tube elements.

Similarities between sieve tubes and companion cells:

1. Food transportation in the plant is done by these two cells.
2. These cells have an elongated shape.
3. Meristem is the emerging point for both cells.