3
Question
(i) It is a non-living, elongated cell with tapering ends. Its wall is highly thickened with
(ii) except at certain circular spots known as (iii). And (iv) is a cylindrical tube-like structure placed one above the other end to end. (v) is a non-living, thick-walled cell providing mechanical support?Select the correct sequence of words to complete the above paragraph.
(i) It is a non-living, elongated cell with tapering ends. Its wall is highly thickened with
(ii) except at certain circular spots known as
(iii). And (iv) is a cylindrical tube-like structure placed one above the other end to end.
(v) is a non-living, thick-walled cell providing mechanical support?
Select the correct sequence of words to complete the above paragraph.
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Solution
The correct option is D (i) Tracheid (ii) Lignin (iii) Pits (iv) Vessel (v) Xylem fibre
Tracheids are elongated cells in the xylem of vascular plants that serve in the transport of water and mineral salts. Tracheids are one of two types of tracheary elements, vessel elements being the other. Tracheids, unlike vessel elements, do not have perforation plates.
All tracheary elements develop a thick lignified cell wall, and at maturity, the protoplast has broken down and disappeared. The presence of tracheary elements is the defining characteristic of vascular plants to differentiate them from non-vascular plants. The two major functions that tracheids may fulfill are contributing to the transport system and providing structural support. The secondary walls have thickenings in various forms as annular rings; as continuous helices (called helical or spiral); as a network (called reticulate); as transverse nets (called scalariform); or, as extensive thickenings except in the region of pits. Pits are parts of plant cell walls that allow the exchange of fluids. In the case of pressure changes in the cell lumen, pit aspiration can occur.
Vessel, also called trachea, in botany, the most specialized and efficient conducting structure of xylem (fluid-conducting tissues). Characteristic of most flowering plants and absent from most gymnosperms and ferns, vessels are thought to have evolved from tracheids (a primitive form of water-conducting cell) by loss of the end walls.
A vessel consists of a vertical series of vessel members that vary from elongated to squat, drum-shaped cells the walls of which are secondarily thickened with rings, spirals, or networks of cellulose, that later become lignified. The length of vessels varies from two cells to rows several meters long. During development, the end walls, already pitted, breakthrough and eventually disappear.
The xylem is the principal water-conducting tissue of vascular plants. It consists of tracheary elements, tracheids, and wood vessels and of additional xylem fibers. All of them are elongated cells with secondary cell walls that lack protoplasts at maturity. Bordered pits are typical for tracheids, while wood vessels are marked by perforated or completely dissolved final walls.
Tracheids are elongated cells in the xylem of vascular plants that serve in the transport of water and mineral salts. Tracheids are one of two types of tracheary elements, vessel elements being the other. Tracheids, unlike vessel elements, do not have perforation plates.
All tracheary elements develop a thick lignified cell wall, and at maturity, the protoplast has broken down and disappeared. The presence of tracheary elements is the defining characteristic of vascular plants to differentiate them from non-vascular plants. The two major functions that tracheids may fulfill are contributing to the transport system and providing structural support. The secondary walls have thickenings in various forms as annular rings; as continuous helices (called helical or spiral); as a network (called reticulate); as transverse nets (called scalariform); or, as extensive thickenings except in the region of pits. Pits are parts of plant cell walls that allow the exchange of fluids. In the case of pressure changes in the cell lumen, pit aspiration can occur.
Vessel, also called trachea, in botany, the most specialized and efficient conducting structure of xylem (fluid-conducting tissues). Characteristic of most flowering plants and absent from most gymnosperms and ferns, vessels are thought to have evolved from tracheids (a primitive form of water-conducting cell) by loss of the end walls.
A vessel consists of a vertical series of vessel members that vary from elongated to squat, drum-shaped cells the walls of which are secondarily thickened with rings, spirals, or networks of cellulose, that later become lignified. The length of vessels varies from two cells to rows several meters long. During development, the end walls, already pitted, breakthrough and eventually disappear.
The xylem is the principal water-conducting tissue of vascular plants. It consists of tracheary elements, tracheids, and wood vessels and of additional xylem fibers. All of them are elongated cells with secondary cell walls that lack protoplasts at maturity. Bordered pits are typical for tracheids, while wood vessels are marked by perforated or completely dissolved final walls.
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