Question

What are the functions of (1) parenchyma (2) collenchyma
(3) schelerenchyma

Answer 1

FUNCTIONS OF PARENCHYMA:

1) It serves as food storage tissue of plants, mainly for starch or fats.
2) The cells of the parenchyma are turgid and help in maintaining shape and firmness of the plant.
3) The intercellular spaces of parenchyma cells allow for gaseous exchange.
4) Certain waste products gum, tannin, resins, latex and mucilage are also stored in parenchyma.
5) Parenchyma containing chlorophyll, chlorenchyma performs photosynthesis.
6)In hydrophytes, parenchyma has large air cavities that provide buoyancy to such plants. Such a parenchyma is called as aerenchyma.

Collenchyma 

●The structure of collenchyma is similar to parenchyma but it is characterized by the deposition of extra cellulose at the corners of the cells.

●Collenchyma is a mechanical tissue, its main function is to provide support to those organs where it is found.

●It is found in the outer regions of cortex (stems, petioles).

Sclerenchyma

●The structure of these cells are roughly spherical, although it may vary considerably in size and shape, the primary cell wall is thickened with the deposits of lignin.

●Their main function is to provide mechanical support and are most commonly found in the cortex, pith phloem, fruits and seeds.


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Answer 2

(1)
In parenchyma tissue all cells are isodiametric and thin walled. The cells may be oval, circular or poly­gonal with intercellular spaces. They are living. This tissue is present in all organs of the plant e.g., roots, stems, leaves, flowers, fruits and seeds.
(2)
Collenchyma cells are longer than parenchyma cell.. They are living. The intercellular spaces in this tissue are absent because in intercellular spaces at the corner of cells thickenings of cellulose and pectin develop due to which the cell wall become rigid and thick at corners. Sometimes collenchyma develops chloroplasts. Collenchyma is usually found as 3-4 layered hypodermis of herbaceous dicotyledonous stem. They are absent in monocot stems.
(3)
This tissue differ from previous tissues in possessing thickened secondary walls which may or may not be lignified. They are of various shapes and sizes when mature. They are dead. They are of two types :

1. Sclerenchymatous fibres 2. Stone cells