Botany and Plant Science

• Sclerenchyma makes plant hard and stiff. The cells of the tissue are dead. They are long and narrow. For example, coconut. The cells of this tissue are dead and its wall is thickened with a chemical substance Lignin. (Lignin is a chemical substance which acts as cement). 
• Sclerenchyma is present in the stems, around the vascular bundle in the veins of the leaves and the hard covering of seeds and nuts. It provides strength to the plant parts.

Lignin is a component of the secondary cell walls of sclerenchyma. Two types of sclerenchyma cells exists- fibres and sclereids. Their walls consist of cellulose, hemicellulose and lignin. Sclerenchyma cells are the principal supporting cells in plant tissues that have ceased elongation.

Fibres and sclereids are two types of sclerenchyma cells. The fibres are generally long, slender cells occurring in bundles. Their walls are thickened by lignin and the principal cell wall material is cellulose. Sclereids are the reduced form of sclerenchyma cells with thickened, lignified walls. So, the correct option is 'lignin, lignin'.

The ground tissue of plants is the supporting tissue which helps the specialized one to carry their function efficiently. The ground tissue includes parenchyma, sclerenchyma, and collenchyma.
Collenchyma cells have thin primary walls with some areas of secondary thickening. Collenchyma provides extra structural support, particularly in regions of new growth.
Sclerenchyma cells have thick lignified secondary walls and often die when mature. Sclerenchyma provides the main structural support to a plant. Ground tissue is a simple tissue. Xylem and phloem come under vascular bundles.
Thus, the correct answer is option A.

The bundle sheath of monocot leaf is made of parenchyma but just above and below the vascular bundles are found sclerenchymatous cells up to epidermis. The bundle sheath of dicot leaf made of parenchyma. Just above and below the vascular bundle, some parenchymatous cells or collenchymatous cells are present up to epidermis. Grass belongs to monocot so, contains sclerenchymatous bundle sheath. Sunflower, banyan and mango are dicot so, contains parenchymatous or collenchymatous bundle sheath. 
Thus, the correct answer is option C.

Companion cells are specialised type of parenchyma cells. The metabolic functioning of sieve-tube members depends on a close association with the companion cells, a specialized form of parenchyma cell. All of the cellular functions of a sieve-tube element are carried out by the (much smaller) companion cell, a typical nucleate plant cell except the companion cell usually has a larger number of ribosomes and mitochondria. The cytoplasm of a companion cell is connected to the sieve-tube element by plasmodesmata.

Tyloses are generally the outgrowth protruding from the parenchyma cells of xylem vessels. It generally protects the vascular tissue during stress like drought or infection. During unfavourable conditions, it falls from the sides of the cells and dam up the vascular tissue to prevent further damage to the plant. It can be traced in the secondary xylem. It aids in the process of making sapwood into heartwood in some hardwood trees, especially in trees with larger vessels. These blockages can be used in addition to gum plugs as soon as vessels become filled with air bubbles, and they help to form a stronger heartwood by slowing the progress of rot.
Thus, the correct answer is option D.

Tissue which develops more due to the scarcity of water is sclerenchyma. Sclerenchyma is the supporting tissue in plants. Two types of sclerenchyma cells exist: fibres and sclereids. Their walls consist of cellulose, hemicellulose, and lignin. Sclerenchyma cells are the principal supporting cells in plant tissues that have ceased elongation. Sclerenchyma is composed of dead cells with extremely thick cell walls -secondary walls that make up to 90% of the whole cell volume.
Thus, the correct answer is option A.

Sclerenchyma is a simple permanent tissue which is mainly composed of dead cells. The walls consist of cellulose, hemicellulose and lignin. These are the principal supporting cells in plant tissues that have ceased elongation. 
Sclerenchyma fibres are of great economical importance, since they constitute the source material for many fabrics (flax, hemp, jute, ramie).

Senescence refers to the loss of functional capacity causing a cellular breakdown and metabolic failure. It is a characteristic feature of the period between reproductive maturity and death of a plant or plant part or cell, which ultimately causes cell death. 

Sclerenchyma cells have thick lignified secondary walls and often die when mature. It provides the main structural support to a plant. They are long and pointed cells. 

Parenchyma is a simple living tissue, which is composed of thin-walled polyhedral, isodiametric living cells with sufficient cytoplasm and one or more nuclei. 

Sclerenchyma is the simple permanent tissue. It commonly forms the protective covering of the nuts and fruits but it also forms the ground tissue which supports different  specialized cells. Their walls consist of cellulose, hemicellulose, and lignin. 

Parenchyma is thin walled, polyhedral, isodiametric, mostly non-lignified, soft living cells with sufficient cytoplasm and one or more nuclei. 

Sclerenchyma cell is a simple permanent tissue which is mainly composed of dead cells. It is the hard, thick walls that make sclerenchyma cells important strengthening and supporting elements in plant parts that have ceased elongation. Their cell walls contain, besides cellulose, a high proportion of lignin. It forms a protective coating on seeds and nuts. Since sclerenchyma cells are dead at maturity, it does not contain plastids. Parenchyma and collenchyma cells are living cells which have plastids.