Tag: permanent tissues and their types
Questions Related to permanent tissues and their types
This is a complex, non-carbohydrate polymer found in cell walls Its function is to provide stiffening to the cell as in xylem vessels and bark fibres. Name it
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Opsonin
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Saponin
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Lignin
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Plant Polypeptide
Lignin is a class of complex organic polymers that form key structural materials in the support tissues of vascular plants and some algae. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity and do not rot easily. Chemically, lignins are cross-linked phenolic polymers. As a biopolymer, lignin is unusual because of its heterogeneity and lack of a defined primary structure. Its most commonly noted function is the support through strengthening of wood (mainly composed of xylem cells and lignified sclerenchyma fibres) in vascular plants.
Hard bast is made up of
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Collenchyma
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Sclerenchyma
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Aerenchyma
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Parenchyma
Bast is the term used for the fibres of phloem. These fibres are tough and resistant with a narrow lumen and secondary walls deposited with lignin. These are dead elongated cells of sclerenchyma tissue. Examples include jute fibres.
If the pericycle is not continuous but as isolated sclerenchyma strips it is called as
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Epiblema
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Phellem
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Hard bast
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Astrosclereids
Pericycle is the outermost layer of the stele. Stele is composed of all tissues inside of the endodermis. Structure of pericycle differs in monocots and in dicots. In dicots, pericycle is in the form of isolated strips of sclerenchyma cells, which are lignified. Each patch is associated with phloem of vascular bundle. Such, pericycle is called as hard bast.
Epiblema are special epidermal cells present in rootlets. They are specially adapted for absorbing liquids. Phellem is outermost layer of cork cambium which is suberised.
Astrosclereids is a type of sclereid which is a large, radially branched structure.
Thus, the correct answer is option C.
In case of monocots, hypodermis is
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Collenchymatous
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Parenchymatous
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Sclerenchymatous
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Both A and B
Hypodermis is present in both dicot and monocot stems. In case of dicots, the hypodermis is made up of collenchyma cells and those present in monocots is made up of sclerenchymatous cells.
Rod-like elongated sclereids in the seed-coats of pulses are called as
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Astrosclereids
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Macrosclereids
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Trichosclereids
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Brachysclereids
Macrosclereids are elongated sclereids. Sclereids are the reduced form of sclerenchyma. It is usually found in the outer layer of seed coat of legumes. These cells are responsible for restricting water uptake by hard seeded legumes.
Which of the following statement (s) is/are true?
(A) Uneven thickening of cell wall is characteristic of sclerenchyma.
(B) Periblem forms cortex of the stem and the root.
(C) Tracheids are the chief water transporting elements in gymnosperms.
(D) Companion cell is devoid of nucleus at maturity.
(E) The commercial cork is obtained from Quercus suber.
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A and D only
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B and E only
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C and D only
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B, C and E only
The cortex of the root and shoot is formed from the periblem. The cortex is the outermost layer on the stem or roots of plants. Cork which is used commercially as bottle stoppers, bulletin boards, coasters, insulation, sealing for lids, flooring, gaskets for engines etc. is obtained from Quercus suber, commonly called as the cork oak, a medium-sized, evergreen oak tree. Since the vessel elements are absent in most gymnosperms, the tracheids form the main elements of xylem that help in transporting water and minerals.
Grittness in pear is due to the presence of
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Brachy sclereids
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Astro sclereids
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Ostero sclerids
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macor sclerids
Sclereids are reduced form of sclerenchyma cells with thick and lignified walls. Grittiness in pear is due to the presence of stone cells called as sclereids. The presence of numberous brachy sclereids makes the texture of pear gritty. The brachy sclereids are isodiametric in shape.
Stereome comprises
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Sclerenchyma
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Collenchyma
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Non-living cells of vascular tissues
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All of the above
Stereome is a mechanical tissue which is formed due to polysaccharide deposition. This is seen in sclerenchyma, collenchyma and all non-living cells of vascular tissues. The deposition of polysaccharides thickens the cell walls in all the three tissue types. Collenchyma is formed due to the deposition of cellulose and is a living tissue. Sclerenchyma is formed due to the deposition of lignin and is a dead permanent tissue.
What chemical substance is deposited in the secondary wall of sclerenchyma?
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Myelin
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Lignin
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Lymph
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Collagen
- Sclerenchyma cells are simple permanent tissue which is composed of dead cells and has secondary cell walls thickened with cellulose and usually impregnated with lignin. It serves two major functions protection and support.
Leaves of Victoria regia are rigid due to
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Stellate parenchyma
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Stellate sclerenchyma
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Osteosclereids
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Macrosclereids
Victoria regia belongs to the genus of water-lilies, from the family Nymphaeceae and inhabits in the still waters of all the rivers of the South American continent. These are characterized by the presence of very large green leaves that are orbiculate, peltate, flat with their margin elevated all around and floating on water surface. The leaves borne on long foot stalks are radiately and reticulately ribbed and the venation of lamina corrugated involute. A cross section reveals the presence of stellate sclerenchyma cells. The sclerenchyma cells with thick nonelastic walls provide the strength and support for these vast leaves