Tag: tissues: plant tissues

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'.

Cork (phellem) is not considered as living tissue. It is a water-resistant, protective tissue that displaces the stem epidermis during the secondary growth phase. A mature cork cell is non-living and has cell walls that are composed of a waxy substance that is highly impermeable to gasses and water called as suberin. Generally, the phloem together with the cork cells is considered to comprise the outer bark. The epidermis cell is a single-layered group of cells that covers plants leaves, flowers, roots, and stems. It forms a boundary between the plant and the external environment. The epidermis serves several functions, it protects against water loss, regulates gas exchange, secretes metabolic compounds and absorbs water and mineral nutrients. Cortex and pericycle are not the protective tissues. 
Thus, the correct answer is option D.

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 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).

The protoderm mainly differentiates to form the dermal layer which is known as epidermis, hypodermis, and endodermis. Hypodermis (exodermis) is the outermost layer of cells in the plant cortex. These cells are modified to give additional structural support or to store food materials or water. After the loss of the piliferous layer of the root, the hypodermis takes over the protective functions of the epidermis.
Thus, the correct answer is option C.