Chapter 6: Anatomy of Flowering Plants Application Questions | biology Class 11 CBSE

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Chapter 6: Anatomy of Flowering Plants Application Questions | biology Class 11 CBSE | ByteNotes.in

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 1

Applied Concept

A student observes a transverse section of a plant organ under a microscope and notes: vascular bundles are arranged in a ring, each bundle is conjoint and open, and a large central pith is present. Which plant organ and plant type does this section belong to? Justify your answer.

The section belongs to the stem of a dicotyledonous plant. The ring arrangement of vascular bundles is the hallmark of a dicot stem, distinguishing it from monocot stems (where bundles are scattered) and roots (where bundles are radial).
Conjoint vascular bundles (xylem and phloem on the same radius) are characteristic of stems and leaves, not roots (which are radial). The 'open' nature of the bundles (cambium present between xylem and phloem) specifically identifies this as a dicot stem, since monocot stem bundles are closed.
The presence of a large central pith is consistent with a dicot stem where a prominent ring of vascular bundles separates the cortex from the central pith. In dicot roots, pith is small or inconspicuous; in monocot stems, there is no distinct cortex-pith boundary.
The student can further confirm by checking for: endodermis as a starch sheath, collenchymatous hypodermis, semi-lunar sclerenchymatous pericycle above phloem, and medullary rays between bundles — all features characteristic only of the dicot stem.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 2

Applied Concept

During a drought period, a farmer notices that the grass in the field has rolled up its leaves. Explain the anatomical basis of this observation and state its adaptive significance.

The leaf rolling is caused by bulliform cells — large, empty, colourless adaxial epidermal cells present along the veins in grass leaves. During drought (water stress), these cells lose water and become flaccid (lose turgor).
The loss of turgor in bulliform cells removes the mechanical tension that normally keeps the leaf lamina flat and exposed. As a result, the leaf curls or rolls inwards longitudinally, reducing the total surface area exposed to the dry, windy atmosphere.
The adaptive significance is water conservation: by rolling inward, the leaf reduces its exposed surface, lowering transpirational water loss. The curled structure also creates a humid microenvironment inside, further reducing the gradient driving evaporation from stomata.
This mechanism is fully reversible — when water becomes available, bulliform cells regain turgor and the leaf unfurls, resuming full photosynthetic activity. This reversibility makes it an energetically cheap and efficient drought-response strategy for grasses.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 3

Applied Concept

With reference to the internal anatomy of a dicot root, explain why an endodermal barrier is necessary and what would happen if Casparian strips were absent.

Casparian strips are water-impermeable suberised bands on the radial and tangential walls of endodermal cells. They block the apoplastic (cell-wall) pathway, forcing all water and dissolved mineral ions to pass through the living cytoplasm (symplast) of endodermal cells before entering the stele.
This mandatory symplastic passage allows the root to selectively regulate which ions enter the xylem — essential nutrients are actively transported in, while harmful ions or toxins can be excluded. Without Casparian strips, any solute in the soil water could freely enter the stele through cell walls, bypassing cellular regulation.
If Casparian strips were absent, soil toxins, excess salts, and unwanted ions would flow freely into the xylem and be transported to leaves and other organs, potentially disrupting cellular metabolism and damaging photosynthetic tissues.
Additionally, without this barrier, the high osmotic pressure maintained in the stele (which drives water uptake) could not be sustained, as solutes would freely diffuse back out — reducing root pressure and the plant's ability to push water upward, especially in conditions of low transpiration.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 4

Applied Concept

A biology student is shown two microscope slides — one of a monocot stem and one of a dicot stem — but they are not labelled. Using your knowledge of plant anatomy, describe the features the student should look for to correctly identify each slide.

The student should first examine the arrangement of vascular bundles: a ring arrangement of vascular bundles indicates a dicot stem, while scattered vascular bundles throughout the ground tissue indicate a monocot stem — this is the most reliable and immediate distinguishing criterion.
Next, check the nature of the vascular bundles: if bundles have cambium between xylem and phloem (open bundles), it is a dicot stem; if bundles lack cambium (closed bundles) and are surrounded by a sclerenchymatous bundle sheath, it is a monocot stem.
Examine the hypodermis: collenchymatous hypodermis (flexible cells) indicates dicot; sclerenchymatous hypodermis (rigid, thick-walled cells) indicates monocot. Also check for a distinct cortex, endodermis (starch sheath), and pericycle — present in dicot, absent as distinct layers in monocot.
Finally, check for phloem parenchyma within the vascular bundles: its presence indicates dicot; its absence (and possible presence of water-containing cavities in bundles) indicates monocot. The presence of medullary rays between bundles is also a dicot feature absent in monocots.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 5

Applied Concept

With reference to the anatomy of a dorsiventral leaf, explain why more stomata are present on the lower surface and how this is related to the leaf's internal structure.

In a dorsiventral leaf, the abaxial (lower) epidermis bears more stomata because this surface is less directly exposed to sunlight and is therefore cooler; lower temperature means lower vapour pressure gradient between the leaf interior and the atmosphere, so water loss per open stoma is less.
The adaxial (upper) surface faces direct solar radiation and higher temperatures; having few or no stomata here prevents excessive evaporative water loss that would occur if stomata were equally distributed on the hotter upper surface.
Internally, the spongy parenchyma (with large interconnected air spaces including sub-stomatal cavities) is positioned adjacent to the abaxial epidermis. The air spaces provide a pathway for CO2 to diffuse from the stomata to the photosynthetically active cells, making the abaxial-stomata arrangement functionally efficient.
The palisade parenchyma is adaxially placed to intercept light efficiently; it does not need direct access to stomata as CO2 can diffuse from the abaxial stomata through the spongy layer and into palisade cells. The anatomical arrangement of mesophyll layers thus complements the stomatal distribution.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 6

Applied Concept

A transverse section of a root shows more than six xylem bundles, a large well-developed pith, and no secondary growth. Identify the root type and explain each observation.

This is a monocotyledonous root. The polyarch condition (more than six xylem bundles) is a defining characteristic of monocot roots, in contrast to the oligarch condition (two to four xylem bundles) of dicot roots.
The large, well-developed pith is characteristic of monocot roots because the numerous xylem bundles radiate outward from the pericycle, leaving a significant parenchymatous region at the centre that develops into a prominent pith. In dicot roots, fewer xylem strands extend to the centre, leaving little or no pith.
The absence of secondary growth is consistent with monocotyledonous roots, which do not form a cambium ring and therefore permanently retain their primary anatomy without any increase in girth over time.
The polyarch xylem arrangement in monocot roots is functionally significant because a greater number of xylem bundles provides more pathways for rapid water conduction from the root surface to the stele, supporting the high water-demand of large monocot plants like sugarcane and maize.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 7

Applied Concept

With reference to the anatomy of the dicotyledonous stem, explain why the pericycle is described as sclerenchymatous patches and not a complete ring, and discuss the functional implication of this.

In the dicot stem, the pericycle is present as semi-lunar (half-moon shaped) patches of sclerenchyma located above the phloem, on the inner side of the endodermis. It does not form a continuous ring because it is only developed where mechanical reinforcement is needed — directly above the phloem of each vascular bundle.
This discontinuous arrangement allows the spaces between sclerenchyma patches to remain as parenchymatous medullary rays, which facilitate lateral transport of water, minerals, and food between the vascular bundles and the pith/cortex.
If the pericycle were a complete sclerenchymatous ring, it would block the medullary rays and prevent lateral translocation of materials between the vascular system and the ground tissue, reducing the metabolic efficiency of the stem.
The semi-lunar sclerenchyma patches provide targeted mechanical support to the phloem — the softer, more vulnerable conducting tissue — without creating a rigid barrier throughout, balancing mechanical protection with the need for continued radial communication between tissue systems.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 8

Applied Concept

A student claims that root hairs and trichomes are structurally identical. Evaluate this claim with reference to the chapter.

The claim is incorrect. Root hairs are unicellular elongations of the epidermal cells (epiblema) in the root, formed from a single cell — they are always unbranched and lack complex structure.
Trichomes are epidermal hairs on the shoot system (stem); they are usually multicellular, composed of more than one cell, and can be branched or unbranched, soft or stiff, and may even be secretory — a structural complexity absent in root hairs.
Functionally, root hairs are specialised for absorption of water and minerals from the soil, whereas trichomes function primarily to prevent water loss through transpiration by trapping a boundary layer of humid air near the leaf or stem surface.
Thus, although both are epidermal appendages arising from the epidermis, they are anatomically distinct (unicellular vs. multicellular), morphologically different (unbranched vs. branched or unbranched), and functionally contrasting (absorption vs. water retention) — the student's claim is anatomically and functionally unsupported.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 9

Applied Concept

In a plant anatomy practical, a student observes a cross section and identifies scattered vascular bundles, each surrounded by a sclerenchymatous bundle sheath, with absent phloem parenchyma. Identify the organ and explain whether this plant will undergo secondary growth.

The described features — scattered vascular bundles, each surrounded by a sclerenchymatous bundle sheath, and absent phloem parenchyma — are the anatomical hallmarks of a monocotyledonous stem.
This plant will NOT undergo secondary growth. The vascular bundles in monocot stems are closed — cambium is absent between the xylem and phloem — so no lateral meristem is present to produce secondary tissues.
Additionally, the scattered arrangement of bundles prevents the formation of a continuous cambium ring (which requires a ring arrangement of vascular bundles connected by interfascicular parenchyma as in dicot stems). Without a cambium ring, organised secondary thickening is impossible.
The monocot stem compensates for the lack of secondary growth through its sclerenchymatous hypodermis, sclerenchymatous bundle sheaths, and the mechanical strength of tightly packed peripheral vascular bundles — achieving rigidity through primary structural investment rather than secondary growth.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 10

Applied Concept

With reference to the anatomy of the dicotyledonous leaf, explain the role of the bundle sheath and its relationship to the veins visible on a leaf surface.

Bundle sheath cells form a complete layer of thick-walled cells that encloses each vascular bundle in the veins of dicot leaves. They physically separate the vascular tissue from the mesophyll, controlling the exchange of materials between them.
The veins visible on the surface of a dicot leaf correspond to the vascular bundles internally — larger, more prominent veins contain larger vascular bundles with more prominent bundle sheaths, while smaller veins have smaller bundles. The reticulate venation pattern of dicot leaves thus directly reflects the internal branching of vascular bundles.
The bundle sheath acts as a loading/unloading interface for phloem: sugars produced in mesophyll cells move into the bundle sheath and then into phloem for translocation. Water and minerals exiting the xylem first enter the bundle sheath before being distributed to mesophyll cells.
By controlling access to the vascular tissue, bundle sheath cells regulate the concentrations of ions and solutes around the xylem and phloem, contributing to maintaining appropriate water potentials and ion gradients necessary for efficient transport.

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Chapter 6: Anatomy of Flowering Plants | Application Questions

A student observes a transverse section of a plant organ under a microscope and notes: vascular bundles are arranged in a ring, each bundle is conjoint and open, and a large central pith is present. Which plant organ and plant type does this section belong to? Justify your answer.

During a drought period, a farmer notices that the grass in the field has rolled up its leaves. Explain the anatomical basis of this observation and state its adaptive significance.

With reference to the internal anatomy of a dicot root, explain why an endodermal barrier is necessary and what would happen if Casparian strips were absent.

A biology student is shown two microscope slides — one of a monocot stem and one of a dicot stem — but they are not labelled. Using your knowledge of plant anatomy, describe the features the student should look for to correctly identify each slide.

With reference to the anatomy of a dorsiventral leaf, explain why more stomata are present on the lower surface and how this is related to the leaf's internal structure.

A transverse section of a root shows more than six xylem bundles, a large well-developed pith, and no secondary growth. Identify the root type and explain each observation.

With reference to the anatomy of the dicotyledonous stem, explain why the pericycle is described as sclerenchymatous patches and not a complete ring, and discuss the functional implication of this.

A student claims that root hairs and trichomes are structurally identical. Evaluate this claim with reference to the chapter.

In a plant anatomy practical, a student observes a cross section and identifies scattered vascular bundles, each surrounded by a sclerenchymatous bundle sheath, with absent phloem parenchyma. Identify the organ and explain whether this plant will undergo secondary growth.

With reference to the anatomy of the dicotyledonous leaf, explain the role of the bundle sheath and its relationship to the veins visible on a leaf surface.

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