Question

Which one of the following characteristic features is not applicable to parenchyma?
A. It forms the major tissue within organs.
B. Cells are generally brick shaped closely packed with intercellular spaces.
C. Their walls are thin and made up of cellulose.
D. Parenchyma performs functions like photosynthesis, storage, secretion, and mechanical support.

Answer 1

Plant tissues in which a group of similar cells present and together with an organized function and are required in various activities of plants such as cellular metabolism like photosynthesis, respiration, regeneration, etc. These cells are used to give elasticity, mechanical strength to organs.

Complete answer:
Parenchyma tissue, a kind of simple permanent tissue that is produced as an important part of the ground tissues i.e. which is not a vascular tissue but a dermis (skin) of the plant part. Parenchyma tissues are non- vascular and they constitute a simple, living, and undifferentiated cell.
Structure of parenchyma cells: these cells are living and also, they possess a prominent nucleus with protoplast. Parenchymatous cells are polyhedral in shape and observed as oval or round. They are composed of a thin cell wall which is further developed from cellulose or hemicelluloses. They are made up of several vacuoles in which water is abundant and serves as a reservoir.
On the basis of their structures, functions, and location parenchyma cells can be divided:
-Chlorenchyma cells; Those cells possess chloroplast and perform out photosynthesis. These cells form the mesophyll tissue of leaves and also occur in the stem of certain plant species.
-Vascular parenchyma; Those parenchyma cells which are connected with the vascular tissues, mainly of two types;
(A) Phloem parenchyma - it is composed of tapering, elongated, and cylindrical cells with a dense cytoplasm, they store food like resins, latex, etc.
(B) Xylem parenchyma- it is composed of thin-walled cells and the cell wall is produced from cellulose. These cells are needed to store food fats, starch as tannins, crystals.
Functions of parenchyma cell:
They act as a reservoir of water and food as a large intracellular space is present. It is needed to store water, food, oil droplets, etc.
These parenchyma cells are helpful to transport various nutrients and some other chemicals.
Parenchyma cells show the property of totipotency i.e. they can transform into other types of cells and serve as the precursor for other cells.
Hence, the correct answer is option (B).

Note: Parenchyma cells; These cells are referred to as fibre-like elongated and are thick-walled. They provide rigidity and strength to the plant.
-Aerenchyma; They are known to occur in aquatic plants because these cells provide buoyancy to the floating plants. Very large intercellular spaces are known to occur. They are necessary as they help in respiration by giving appropriate oxygen to the aquatic plants.
-Epidermis parenchyma: they are known to occur in the epidermis of the leaves of some gymnosperms. No intercellular spaces are known to occur in these. They constitute a cutinized cell wall.