Tag: plant tissues

The chief mechanical tissue of the plant body composed of highly thick walled cell with little or no protoplasm is called as sclerenchyma.

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.

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 is the tissue which makes the plant hard and stiff.

• Osteosclereids are also known as bone cells. It is a type of sclereid that forms the hypodermal layer in seeds, fruits, and leaves of some plants (dicots).
• It was first seen in the seed coat of Pisum during the maturation. These are the columnar cells that are dilated at the ends.
  So, the correct option is B.

In stems and leaves of monocots, collenchyma is absent. Instead, sclerenchyma is present in monocots. Xylem parenchyma consists of living cells of parenchyma, which are thick and their secondary cell wall is lignified. Sieve tube member is associated with one or more specialized parenchyma cells called as companion cells. Phloem fibres are generally present in the secondary phloem.
Thus, the correct answer is option B.

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).