The categories of sclereids are ___________. a. Macrosclereids b. Osteosclereids c. Tracheids d. Asterosclereids Which of the statements given above is/are correct ?
- (1)Only a
- (2)Only a and b
- (3)a, b and d
- (4)a, b and c
Correct — option (3), a, b and d (statements a, b and d). Sclereids are one of the two cell types that make up sclerenchyma, the dead-at-maturity, thick, lignified-walled plant tissue that provides mechanical support; the other sclerenchyma type is fibres, which are long and narrow, while sclereids are typically shorter and more variably shaped. Botanists classify sclereids into several named categories based on their shape, and the classical list includes brachysclereids or stone cells (roughly isodiametric, as in pear and guava fruit flesh), macrosclereids (elongated, rod- or column-shaped, forming a palisade-like layer in the seed coats of legumes) — statement a — osteosclereids or bone cells (bone- or dumbbell-shaped, with expanded, often lobed ends, found in leaves and seed coats) — statement b — astrosclereids or asterosclereids (branched, star-shaped, found in the leaves and petioles of many hydrophytes such as the water lily, Nymphaea) — statement d — and the more elongated, hair-like trichosclereids and filiform sclereids. Statement c, tracheids, does not belong on this list: a tracheid is a xylem tracheary element, a long, tapering, dead water-conducting cell with pitted walls, part of the plant's vascular (water-transport) tissue system, not a member of the sclereid family of sclerenchyma support cells at all — the two are structurally, functionally and developmentally distinct cell types that happen to share the trait of being dead and lignified at maturity, which is likely why the question uses it as the false option.
- (1)Only a — This keeps only macrosclereids as a correct category, but osteosclereids and astrosclereids are equally well-established, named sclereid categories in standard plant anatomy classification — restricting the correct set to macrosclereids alone incorrectly excludes two genuine sclereid types.
- (2)Only a and b — This keeps macrosclereids and osteosclereids as correct but leaves out astrosclereids (statement d), which is just as standard a named sclereid category — the branched, star-shaped cells found in hydrophyte leaves and petioles such as Nymphaea. Omitting a genuine category understates the full correct set.
- (4)a, b and c — This keeps the two correct categories, macrosclereids and osteosclereids, but swaps in tracheids (statement c) in place of astrosclereids. Tracheids are xylem water-conducting cells, part of the vascular tissue system, not a category of sclereid at all, so including them alongside genuine sclereid types mixes two unrelated plant cell classifications together.
Sclerenchyma is one of the two main types of simple permanent tissue providing mechanical strength in plants (the other being collenchyma, which is living and flexible), and it is made of dead cells with thick, lignified secondary walls. Sclerenchyma itself is divided into two broad cell types: fibres, which are long, narrow and pointed, typically running in bundles alongside vascular tissue or in the cortex/pericycle; and sclereids (also called stone cells or sclerotic cells), which are much more variable in shape and are classified into named subtypes by their form — brachysclereids/stone cells, macrosclereids, osteosclereids, astrosclereids, trichosclereids and filiform sclereids. Sclereids occur scattered singly or in groups within otherwise soft tissue, giving gritty texture to fruits like pear and guava, forming the hard seed coat layer in many legumes, and reinforcing leaves in hydrophytes.
MPSC's botany section regularly tests whether a candidate can correctly separate a genuine named subtype within one plant-tissue classification (sclereids, here) from a plausible-sounding but unrelated cell type belonging to a different classification altogether (tracheids, which are xylem elements, not sclerenchyma). The habit rewarded is checking each listed term against the specific classification the question is actually about, rather than accepting any term that 'sounds like' it could belong on the list because it shares surface features (both are dead, lignified, thick-walled cells).
- Sclerenchyma comprises two cell types: fibres (long and narrow) and sclereids (variably shaped, also called stone cells).
- Named sclereid categories include brachysclereids/stone cells, macrosclereids, osteosclereids, astrosclereids (asterosclereids), trichosclereids and filiform sclereids, classified by shape.
- Osteosclereids ('bone cells') have expanded, often lobed ends resembling a bone, and are found in leaves and seed coats; astrosclereids are branched and star-shaped, typical of hydrophyte leaves such as Nymphaea.
- Tracheids are xylem tracheary elements — long, tapering, pitted, water-conducting cells of the vascular tissue system — and are not a category of sclereid, despite also being dead and lignified at maturity.
a, b and d are real sclereid types; tracheids belong to xylem, a different tissue system.
- Assuming any dead, thick-walled, lignified plant cell must be a sclereid, when tracheids (xylem) and fibres (the other sclerenchyma type) share those traits but belong to different classifications
- Confusing osteosclereids (bone-shaped, lobed ends) with astrosclereids (branched, star-shaped) when a question lists both as options
- Treating 'sclereid' and 'sclerenchyma' as synonyms, when sclereids are specifically one of the two cell types that make up sclerenchyma tissue
MPSC's biology section frequently lists several named subtypes under one plant-tissue classification and slips in one term from an unrelated classification, testing precise recall of which named cell types genuinely belong together rather than superficial pattern recognition.
No directly related past PYQ was found.
- practice — not a real PYQ
Which of the following is NOT a category of sclereid ?
- (a)Brachysclereid
- (b)Osteosclereid
- (c)Vessel element
- (d)Trichosclereid
Answer(c) Vessel element — like tracheids, vessel elements are xylem tracheary elements belonging to the vascular tissue system, not a category of sclereid, which is a sclerenchyma cell type.
- practice — not a real PYQ
Astrosclereids, the branched, star-shaped sclereids that reinforce leaves and petioles, are typically found in which kind of plant ?
- (a)Xerophytes
- (b)Hydrophytes
- (c)Epiphytes
- (d)Parasitic plants
Answer(b) Hydrophytes — astrosclereids are characteristic of water plants such as Nymphaea (water lily), where they help support the otherwise soft, buoyant leaf and petiole tissue.