Question

Given below are some characteristics of vessels and tracheids.
(i) Multicellular with wide lumen
(ii) Dead cells
(iii) Cell walls are lignified
(iv) Discontinues lumen due to presence of end walls
(v) Long, cylindrical tube-like structure
(vi) Elongated cells with tapering ends
Categorize the above characteristics with vessels (x) and tracheids (y) and select the correct option.

• A. X- (i), (ii), (iii), (v), Y- (ii), (iii), (iv), (vi)
• B. X- (i), (iii), (vi), Y- (ii), (iii), (iv), (v)
• C. X- (i), (iv), (v), Y- (ii), (iv), (v), (vi)
• D. X- (i), (ii), (v), (vi), Y- (i), (iii), (iv), (vi)

Answer 1

The correct option is A X- (i), (ii), (iii), (v), Y- (ii), (iii), (iv), (vi)

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 metres long. During development, the end walls, already pitted, break through and eventually disappear. Vessel elements are the building blocks of vessels, which constitute the major part of the water transporting system in those plants in which they occur. Vessels form an efficient system for transporting water (including necessary minerals) from the root to the leaves and other parts of the plant.
In secondary xylem the xylem which is produced as a stem thickens rather than when it first appears a vessel element originates from the vascular cambium. A long cell, oriented along the axis of the stem, called a "fusiform initial", divides along its length forming new vessel elements. The cell wall of a vessel element becomes strongly "lignified", i.e. it develops reinforcing material made of lignin. The side walls of a vessel element have pits: more or less circular regions in contact with neighbouring cells. At maturity the protoplast the living material of the cell dies and disappears, but the lignified cell walls persist. A vessel element is then a dead cell, but one that still has a function, and is still being protected by surrounding living cells.
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 formsas 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.