31 Years NEET Previous Year Questions: Anatomy of Flowering Plants - 1

• The monocot stem has a sclerenchymatous hypodermis, a large number of scattered vascular bundles, each surrounded by a sclerenchymatous bundle sheath, and a large, conspicuous parenchymatous ground tissue. Thus statement (c) is incorrect because the hypodermis is typically sclerenchymatous (providing mechanical support), not parenchymatous.
• Vascular bundles are conjoint and closed — true: xylem and phloem occur together and cambium is absent in each bundle.
• Peripheral vascular bundles are generally smaller than the centrally located ones — true: bundle size often varies across the stem cross-section.
• The phloem parenchyma is absent, and water-containing cavities may be present within some monocot vascular bundles — true: phloem parenchyma is typically not seen in monocot stems.

Bulliform cells are specialised, large, thin‑walled cells found in the upper (adaxial) epidermis of many monocot leaves, especially grasses. Their main role is to regulate leaf folding or rolling in response to water stress. When turgor in bulliform cells is high (well‑watered conditions) the leaf remains expanded; when these cells lose water and become flaccid, the leaf rolls or folds inward, reducing exposed surface area and thereby reducing transpiration and water loss.
Optionwise brief evaluation:
Option A: Correct — bulliform cell collapse causes inward curling (leaf rolling) in monocots.
Option B: Incorrect — salt stress responses involve ion regulation and other mechanisms; bulliform cells are primarily involved in drought/water conservation.
Option C: Incorrect — bulliform cells do not directly increase photosynthesis; they modulate leaf position which can indirectly affect light interception.
Option D: Incorrect — bulliform cells are not storage cells for sugars; they function in leaf movement through changes in turgor.

Guard cells (label C in the figure) have a thin outer wall (facing the epidermis) and a strongly thickened inner wall (adjacent to the stomatal pore). This differential wall thickness causes the guard cells to bow out when turgid, opening the pore, and to collapse together when flaccid, closing it.

Statement I: Parenchyma is living but collenchyma is dead tissue.
This statement is False. Both parenchyma and collenchyma are living simple tissues. Parenchyma cells are thin‑walled and primarily involved in storage, photosynthesis and repair, while collenchyma cells are living cells with unevenly thickened primary walls that provide flexible mechanical support to growing parts.
Statement II: Gymnosperms lack xylem vessels but presence of xylem vessels is the characteristic of angiosperms.
This statement is True. Gymnosperms mainly have tracheids (no true vessels), whereas angiosperms commonly possess vessels (vessel elements) in their xylem, which are more efficient for water conduction.
Therefore, (c) is correct: Statement I is False but Statement II is True.

In a monocot root, the internal tissue layers from the outside (periphery) to inside (centre) are arranged as follows:

1. C. Epidermis – outermost protective single cell layer.
2. E. Cortex – region of parenchyma beneath the epidermis for storage and transport.
3. A. Endodermis – innermost cortex layer containing Casparian strips; it regulates movement into the stele.
4. D. Pericycle – a thin layer just inside the endodermis from which lateral roots originate.
5. B. Pith – central parenchymatous region prominent in many monocot roots.

Thus, the correct sequence is: C (Epidermis) → E (Cortex) → A (Endodermis) → D (Pericycle) → B (Pith)
Hence, Option (c) is correct.

The figure represents a Vessel (d). Vessels (vessel elements) are elongated, tube‑like xylem elements with perforation plates at the ends and thick, lignified secondary walls. They conduct water efficiently and are characteristic of most angiosperms. Tracheids are narrower and lack open perforations between cells; xylem parenchyma and fibres differ in wall thickness and living status.

• A: True — Companion cells are metabolically active cells adjacent to sieve tube elements; they facilitate loading/unloading of solutes and help maintain the osmotic and pressure gradients required for phloem translocation.
• B: True — Gymnosperms generally lack true vessel elements; water conduction is mainly via tracheids.
• C: True — Mature xylem vessels are dead, hollow tubes that lack cytoplasm to allow unobstructed water flow.
• D: True — Xylem fibres may be septate (with cross walls) or aseptate (without cross walls) depending on the species.
• E: False — Mature sieve tube elements lack a nucleus (and often have reduced organelles) and depend on companion cells for many functions; they do contain cytoplasm but not a functional nucleus.

Therefore, statements A, B, C and D are correct — Option (c) is the best choice.

Statement I: In collenchyma, cell walls are thickened at corners due to deposition of cellulose, hemicellulose, and pectin.
This statement is True. Collenchyma cells have unevenly thickened primary cell walls, especially at the corners, composed mainly of cellulose, hemicellulose and pectic substances; they provide flexible support to young organs.
Statement II: Sclerenchyma consists of lignified cell walls and possesses pits.
This statement is True. Sclerenchyma cells (fibres and sclereids) have heavily lignified secondary walls and often show pits (for limited radial transport) — they provide rigid mechanical support.
The correct answer is (a) Both Statement I and Statement II are True.

Sclereids are specialised sclerenchymatous cells with thick, lignified walls that impart hardness and a gritty texture. They are commonly found in the hard seed coats and fruit walls of nuts, and also produce the gritty texture of pear pulp (stone cells). Their presence explains the gritty sensation when eating pears.

Companion cells are closely associated with sieve tube elements in angiosperms. They actively load sugars and other solutes into sieve tubes and help maintain the osmotic differences that generate the pressure gradients required for mass flow (phloem transport). Sieve tube elements are enucleate or nearly so and rely on companion cells for metabolic support; thus companion cells are essential for maintaining the functional pressure gradient.

Statement I: In most dicot leaves, stomata are more numerous on the abaxial (lower) epidermis than on the adaxial (upper) epidermis; this reduces direct exposure to sunlight and helps limit water loss. Therefore, Statement I is generally False (exceptions exist in some xerophytic leaves).
Statement II: Palisade parenchyma is composed of elongated, columnar cells arranged vertically (perpendicular to the leaf surface) and packed with chloroplasts; they are located on the adaxial side and maximise light absorption. Thus Statement II is True.
Hence, only Statement II is correct — Option (b).

• Statement I: Incorrect — the terms endarch and exarch are used to describe the developmental sequence of primary xylem (protoxylem and metaxylem), not secondary xylem. In endarch condition protoxylem is innermost and metaxylem towards the periphery (typical of stems); in exarch the protoxylem is peripheral and metaxylem central (typical of roots).
• Statement II: True — the exarch condition (protoxylem towards periphery and metaxylem towards centre) is typical and most common in roots.

Therefore, Statement I is incorrect and Statement II is true — Option (d).

A. True. Lenticels are small, lens‑shaped openings in the bark that permit gas exchange between internal tissues and the atmosphere.
B. False. Bark produced early in the season (spring) is generally less woody and is often termed “soft bark”; hard bark is usually produced later in the season.
C. Partly True (but often interpreted differently in various texts). Conventionally, in plant anatomy, “bark” refers to all tissues outside the vascular cambium (this includes periderm and secondary phloem). However, many question keys distinguish between the technical phrase “bark = periderm + secondary phloem” (equivalent to D) and broader non‑technical usage. Because of such ambiguity in some exam keys, the intended correct pair given here is A and D.
D. True. Bark commonly refers to the outer protective tissues, primarily the periderm (outer bark) together with the secondary phloem (inner bark).
E. False. Phellogen (cork cambium) is usually multilayered in active tissues; it is not strictly single‑layered in most species.
Note: There is some variation in how different sources phrase the definition of “bark.” Following the exam key provided here, Option (c) (A and D only) is chosen.

(a) True. Monocot roots typically exhibit polyarch xylem arrangements and have a distinct endodermis and pericycle.
(b) False. Dicot roots usually have fewer than six xylem bundles and do not exhibit polyarch arrangements.
(c) False. Dicot stems have a different vascular arrangement and do not show polyarch xylem.
(d) False. Monocot stems do not typically have polyarch xylem; they have scattered vascular bundles.

(a) A, B, D, C: Correct. From the pith outwards in a stem undergoing secondary growth the usual order is: primary xylem (formed during primary growth) → secondary xylem (formed by vascular cambium towards inside) → secondary phloem (formed by cambium towards outside) → primary phloem (original primary tissue pushed further outward). Thus option (a) gives the correct positional sequence
(b) B, A, C, D: This sequence is incorrect. It suggests that secondary xylem (B) is closest to the pith, followed by primary xylem (A), which is not accurate as primary xylem is formed first during primary growth.
(c) A, B, C, D: This sequence is also incorrect. While it correctly places primary xylem (A) and secondary xylem (B) in order, it incorrectly positions primary phloem (C) before secondary phloem (D), which is not how they are arranged in a mature dicot stem.
(d) B, A, D, C: This sequence is incorrect as well. It incorrectly places secondary xylem (B) before primary xylem (A) and also misplaces the phloem types, suggesting a structure that does not exist in typical dicotyledonous stems.
Understanding the arrangement of these tissues is crucial for comprehending how dicotyledonous plants grow and develop, especially in terms of their vascular system and secondary growth capabilities.

Initiation of lateral roots and the formation of vascular cambium (in many dicot roots) are events that involve the pericycle. Pericycle cells can dedifferentiate and divide to form the root primordia and contribute to cambial activity; epiblema (root epidermis), cortex and endodermis do not typically dedifferentiate to give lateral roots or vascular cambium.

Statement a: In roots, xylem and phloem are arranged alternately in different radii (radial vascular arrangement), which is correct.
Statement b:
Conjoint closed vascular:

• Xylem and phloem lie together along the same radius as in stems and leaves (conjoint).
• In closed bundles, cambium is absent — hence they do not give secondary growth.

Statement c: Open vascular bundles have cambium between xylem and phloem, and hence can produce secondary xylem and phloem (secondary growth).
Statement d: Endarch condition (protoxylem towards centre, metaxylem towards periphery) is characteristic of dicot stems; thus this statement is correct.
Statement e: Monocot roots are often polyarch (more than six xylem arms/bundles), so this statement is correct.
All five statements (a), (b), (c), (d) and (e) are correct — Option (b).

The cells of medullary rays, adjoining these intrafascicular cambium become meristematic and form the interfascicular cambium.

In a large tree, only the outer secondary xylem (sapwood) serves in water conduction, while the inner part (heartwood) is composed of dead but structurally strong secondary xylem and is darker in colour due to the deposition of tannins, resins and oils.

In grasses, certain adaxial epidermal cells along the veins modify themselves into large, empty, colourless cells. These are called bulliform cells. When the bulliform cells in the leaves have absorbed water and arc turgid, the leaf surface is exposed. When they are flaccid due to water stress, they make the leaves curl inwards to minimise water loss.

• Vascular cambium is a type of lateral meristem that produces secondary tissues (xylem and phloem) during secondary growth. 
• It is produced by two types of meristem: intrafascicular cambium (primary meristem occurring as strip in vascular bundles) and interfascicular cambium (secondary meristem which develops from permanent cells of medullary rays which occur at the level of intrafascicular strips).
• The cells of vascular cambium are of two types : fusiform initials which produce secondary xylem towards outside and secondary phloem towards inner side and ray initials which give rise to vascular rays.

Cells of vascular cambium divide periclinal both on the outer and inner sides to form secondary permanent tissues, i.e., secondary xylem and secondary phloem.

The vascular bundles are arranged in a loose circle inside the endodermis of a monocot root. In a monocot root, more than six vascular bundles are present. It shows polyarch condition.

 Gymnosperms lack xylem fibres. Large amount of parenchymatous cells are present with secondary xylem tracheids. So, these are also known as softwood spermatophytes.

Stem of maize has water containing cavities  in vascular bundles.

In closed vascular bundle cambium is absent between xylem and phloem.

Companion cells are narrow, elongated and thin walled living cells. They lie on the sides of the  sieve tubes and are closely associated with them through compound plasmodesmata. It is supposed that the nuclei of the companion cells control the activities of the sieve tube through plasmodesmata. Companion cells also help in maintaining a proper pressure gradient in the sieve tube elements.

The common bottle cork is the product of phellogen. Phellogen produces cork or phellem on the outer side. It consists of dead and compactly arranged rectangular cells that possess suberised cells walls. The cork cells contain tannins. Hence, they appear brown or dark brown in colour.

In Kranz anatomy, the bundle sheath cells have thick wall, no intracellular spaces and large number of chloroplasts.

Open means presence of cambium during secondary growth. Vascular cambium divides to form secondary xylem towards inner side while secondary phloem towards outside.