Tag: permanent tissues and their types

Parenchyma, collenchyma and sclerenchyma are called as simple tissues as they are made up of similar kind of cells. Vascular tissue is a complex tissue because it is heterogeneous in nature with different types of cells. The chief elements are xylem, phloem and pericycle.
Thus, the correct answer is option B.

• Sclerenchyma cells are dead cells at maturity and have a very thick cell wall due to the deposition of lignin. 
  
• They are either present in the form of fibres or sclereids (stone cells).
• They are located in the leaf veins, hard coverings of the seeds and vascular bundle. 
• Its main function include- 1) provide rigidity and mechanical support to the plant body, 2) It also makes the plant stiff and hard.
• So, the correct answer is 'Sclerenchyma'.

Fibres are usually long, spindle shaped structures, with tapering or blunt ends. Secondary thickening by lignin occur in 90% of the area of the cell. Fibres are grouped into xylary fibres and extraxylary fibres. Xylary fibres are also called wood fibres and are the longest among xylem elements. 
Thus, the correct answer is option A.

Sclerenchyma cells occur in many different shapes and sizes, but two main types occur: fibres and sclereids. Fibres are greatly elongated cells whose long, tapering ends interlock, thus providing maximum support to a plant. They often occur in bundles or strands and can be found almost anywhere in the plant body, including the stem, the roots, and the vascular bundles in leaves

• Sclereids or stone cells are a type of reduced sclerenchyma cells.
  
• These stone cells form hard structures such as seed coats and nut shells and provide support to the soft tissues.
• Their cell wall is highly thickened and lignified which form small bundles of durable layers of tissues.
• The presence of numerous stones cells that makes pear and guava have a gritty texture is brachysclereids (unbranched, short and isodiametric with pits).
• The stone cells in tea leaves that make it tougher are astrosclereids (branched as star-shape).

Parenchyma cells have thin cellulosic cell walls. Collenchyma cells have thicker cellulosic walls and also may have pectin deposition on corners. Sclerenchyma cells have thick lignified cell walls and are dead at maturity and provide protection to the different parts of the body. Epithelial cells are thin-walled and living.

Sclereids are a reduced form of sclerenchyma cells with highly thickened, lignified cellular walls that form small bundles of durable layers of tissue in most plants. 

Vascular tissues concerned in the transportation of water, mineral and food.

Phloem is a vascular tissue or conducting tissue, meant for the translocation of organic solutes or food.

Collenchyma is a simple permanent living mechanical tissue, provides elasticity to the young stems.

Mechanical tissues are the rigid cellular tissues, provides elasticity, flexibility to the different parts of the plant body. These are called stereome. So, the correct answer is 'Mechanical tissue’.

Walls of sclerenchyma cells are lignified, which make them thick. Due to this, are no intercellular spaces between them. Hence, option B is correct.