Question

Read the following statements
(i) The sieve tube elements and companion cells are connected by pit fields present between their common longitudinal walls.
(ii) Phloem parenchyma is made of elongated non-tapering cylindrical cells that have a scanty cytoplasm.
(iii) Phloem fibers are made of parenchymatous cells.
(iv) Companion cells help in maintaining the pressure gradient in the sieve tube.
 (v) The phloem parenchyma stores food material and other substances like resins, latex, and mucilage.

How many of the given statements are correct?
A ) Three
B ) Two
C ) One
D ) Four

Answer 1

Hint:The new cells which formed the divisions of cells of primary and secondary. Meristem become structurally and functionally specialised and lose the ability to divide, these newly formed cells are called permanent or mature cells and tissues formed by the cells are permanent tissue.

Complete answer:
Statement i) is correct because the common longitudinal wall present between sieve tube element and companion cell is usually thin and contains pit fields. Pit fields were all areas of greatly reduced thickness which look like holes in the wall.

Statement ii) is incorrect because phloem parenchyma is composed of living parenchymatous cells . These are the elongated cells which have tapering ends and are cylindrical in shape. The cells have dense cytoplasm and prominent nuclei.

Statement iii) is incorrect because phloem fibre are sclerenchymatous fibres. They are also called bast fibres. These are much elongated fibres which do not have branches. The cell wall of phloem fibres is quite thick due to which they provide mechanical support to the plant, at the maturity these fibres lose their protoplasm and become dead.

Statement iv) is correct because companion cells are the specialised parenchymatous cells which are closely associated with sieve tube elements due to which they are called the companion cells. The companion cells help in maintaining the pressure gradient in sieve tubes; the pressure gradient can be defined as differences in pressure that decide the direction of flow of fluid.

Statement v) is correct because the cells of phone parenchyma perform the main function of storing the food synthesized by the cell carrying out photosynthesis. They also help in the transport of food.
These cells also stored organic materials like resins, tannins, milage ( thick glue substance), latex ( the milky fluid) and can be seen exuding from the plant.

Therefore, i), iv) and v), these three statements are correct.

Thus, the correct answer is option (A) Three.

Note:Pit fields are present between the common longitudinal wall of sieve tube elements and companion cells as these two are longitudinally attached with each other. The pit field enables the easy transfer of materials between them hence pitfalls maintain close cytoplasmic connections between sieve tube element and companion cells in contrast to sieve tube elements the companion cells retain a nucleus throughout their life.