The categories of sclereids are ___________.
a. Macrosclereids
b. Osteosclereids
c. Tracheids
d. Asterosclereids
Which of the statements given above is/are correct ?

Question

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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.

Why the other options are wrong — (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.  (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.  (d) 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.

Concept: 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.

State PCS 2025 Q60 — Science & Technology PYQ with Answer

State PCS 2025 Q60 — Science & Technology PYQ with Answer