Tag: tissues: plant tissues

Parenchyma cells are thin-walled, flexible and loosely packed cells. They are alive at maturity. Their shape changes as per function. 
Collenchyma cells are living, elongated and irregularly thickened at corners with less intercellular space. 
Sclerenchyma is a type of permanent tissue. They are dead, elongated, thin, narrow cells with thickened walls without any internal space. Therefore, option C is correct.  

• Sclerenchyma cell is a simple permanent tissue which is mainly composed of dead cells. It provides strength and rigidity to the stem. 
• It forms the protective covering of nuts and fruits. Their cell walls contain, besides cellulose, a high proportion of lignin. 
• It forms a protective coating on seeds and nuts.

Collenchyma contains living, elongated cells with protoplasm at maturity. 
Parenchyma cells are thin-walled, flexible and loosely packed cells. They are alive at maturity. Their cells show protoplasm at maturity.
Sclerenchyma cells are dead, long, thin, narrow with thickened walls without any internal space. They do not possess any protoplasm at maturity. Hence, option A is correct. 

• Sclereids are a reduced form of sclerenchyma cells with highly thickened, lignified walls. These have the shape of a star. They are small bundles of sclerenchyma tissue in plants that form durable layers, such as the cores of apples and the gritty texture of pears (Pyrus communis). 
• Sclereids are variable in shape. The cells can be isodiametric, prosenchyma, forked or elaborately branched. 
• They can be grouped into bundles, can form complete tubes located at the periphery or can occur as single cells or small groups of cells within parenchyma tissues.
•  But compared with most fibers, sclereids are relatively short. Sclerenchyma, tracheids, and collenchyma do not cause the Grittiness of the fruit wall. 

1. Parenchyma forms the major component within organs and are closely packed or have intercellular space and are living with the ability of division. They perform functions of photosynthesis, storage, and secretion.
2. Sclerenchyma is long, narrow cells with thick and lignified cell walls having a few or numerous pits. These are commonly found in fruit wall of nuts, the husk of the coconut, seed coat of legumes, etc.
3. Collenchyma is found in the hypodermis in dicot plants and provide mechanical support to the plant.
4. Chlorenchyma is the modified parenchymatous tissue that helps in photosynthesis.

The shape of the sclerenchyma cells are elongated and cell walls are thickened by lignin. The plant gets very strong support and strength since these are heavily deposited with lignin. It is responsible for the stiffness of coconut fibres. 

Since dead cells can provide mechanical strength as easily as live ones and need less maintenance.

The chief mechanical tissue of the plant body composed of highly thick walled cell with little or no protoplasm is called as sclerenchyma. The main function of sclerenchymatous tissues is to give support to the plant. It also provides hardness and protective covering to seed and nuts.
Therefore, the correct answer is option C.

The chief mechanical tissue of the plant body composed of highly thick walled cell with little or no protoplasm is called as sclerenchyma. Sclerenchyma consist of lignin. Lignin deposition is so thick that the cell walls become strong, rigid and impermeable to water. 

The chief mechanical tissue of the plant body composed of highly thick walled cell with little or no protoplasm is called as sclerenchyma. The thickening of cell wall is due to deposition of cellulose or lignin or both. Lignin deposited cells are said lignified. Sclerenchyma cells are dead at maturity because of the absence of protoplast.