Chapter 5: Morphology of Flowering Plants Application Questions | biology Class 11 CBSE

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Chapter 5: Morphology 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 farmer notices that wheat plants growing in his field have a different root system compared to mustard plants. With reference to the root systems, explain the structural and functional differences and how they relate to the crops' water absorption strategies.

Wheat (monocot) has a fibrous root system — numerous roots of similar thickness arising from the stem base — that spreads widely in the upper layers of soil, efficiently absorbing surface moisture from shallow depths.
Mustard (dicot) has a tap root system — a prominent primary root with secondary and tertiary laterals — that penetrates deep into the soil, accessing water from deeper layers and providing firm anchorage against wind.
In drought conditions, the tap root system of mustard allows access to sub-soil moisture while the fibrous roots of wheat are more dependent on surface rainfall, making mustard relatively more drought-tolerant.
The fibrous root system of wheat, by binding large volumes of topsoil, also prevents soil erosion more effectively than the tap root, demonstrating that root architecture has both agronomic and ecological significance.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 2

Applied Concept

A botanist examines two plants. Plant A has leaves where the leaf base forms a sheath covering the stem, while Plant B has a leaf base bearing two small lateral leaf-like structures. Identify the type of leaf base modification in each case and explain its significance.

Plant A shows the monocotyledonous leaf base modification: the leaf base expands into a sheath that partially or wholly covers the stem, providing additional mechanical support to the weak stem of monocots like grasses, wheat, and maize.
Plant B shows stipules at the leaf base — two lateral, small leaf-like structures that may be free or adnate to the petiole; stipules are present in many dicotyledonous plants and serve protective and photosynthetic functions in some species.
In some leguminous plants (dicots), the leaf base becomes swollen into a pulvinus — a specialised structure involved in sleep movements (nyctinasty) allowing the leaf to fold at night or in response to touch, as in Mimosa pudica.
The presence or absence of stipules and the nature of the leaf base are diagnostic taxonomic characters used to identify plant families; for instance, stipules are characteristic of Rosaceae and Fabaceae families.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 3

Applied Concept

A student observes that in one plant, the main shoot tip produces a flower and all subsequent flowers are produced below it. In another plant, the main shoot continues to grow and new flowers keep appearing from the side. Identify the type of inflorescence in each case and explain the developmental difference.

Plant 1 shows cymose inflorescence: the main axis terminates in a flower (determinate growth), limiting further elongation; subsequent flowers arise from lateral axes in basipetal order (older flowers on top), as seen in cotton and Solanum.
Plant 2 shows racemose inflorescence: the main axis retains indeterminate growth and continues to elongate; flowers arise from lateral branches in acropetal succession (older flowers at the base, younger toward tip), as seen in mustard and radish.
The developmental difference lies in the fate of the apical meristem: in cymose types, it differentiates into a terminal flower (determinate), while in racemose types, the apical meristem remains vegetative and keeps producing lateral floral buds (indeterminate).
This difference in inflorescence type affects flowering duration and pollination success: racemose inflorescences allow prolonged flowering extending the pollination window, whereas cymose types concentrate flower production within a shorter, synchronised period.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 4

Applied Concept

With reference to the chapter, a botanist writes the floral formula: ⊕ ♀ K(5) C(5) A5 G(2). Decode this formula and identify the likely plant family it belongs to.

⊕ indicates actinomorphic (radially symmetrical) flower; ♀ indicates female/bisexual flower. K(5) means calyx with 5 united sepals (gamosepalous); C(5) means corolla with 5 united petals (gamopetalous).
A5 indicates 5 free stamens; the superscript or attachment notation for epipetalous would be included if present. G(2) means the gynoecium has 2 fused carpels (bicarpellary, syncarpous); the line position on G indicates ovary position.
This formula corresponds to family Solanaceae: 5 united sepals, 5 united petals with valvate aestivation, 5 stamens that are epipetalous, bicarpellary syncarpous superior ovary with axile placentation.
Common Solanaceae members whose flowers match this formula include tomato (Lycopersicon esculentum), brinjal (Solanum melongena), potato (Solanum tuberosum), and tobacco (Nicotiana tabacum), all of which are economically important plants.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 5

Applied Concept

A horticulturist examining two flowers notices that in one flower (X), the petals just touch at the margins without overlapping, while in flower (Y), each petal margin overlaps the next in a consistent direction. Name the aestivation type in each and give examples of plants showing these patterns.

Flower X shows valvate aestivation — in this type, sepals or petals in the bud touch each other at the margins without any overlapping; this is seen in Calotropis and members of the family Solanaceae (petals of Solanum).
Flower Y shows twisted (contorted) aestivation — one margin of each petal overlaps the margin of the next petal in a consistent direction (either all clockwise or all anticlockwise), as in china rose (Hibiscus), lady's finger (Abelmoschus), and cotton (Gossypium).
The twisted aestivation pattern creates a tight spiral in the bud that provides more uniform and complete protection to the inner floral parts compared to valvate aestivation, which provides minimal but even coverage.
Aestivation type is a useful character in plant identification: twisted aestivation is a characteristic feature of family Malvaceae (to which china rose and cotton belong), while valvate aestivation is typical of Solanaceae and some Liliaceae members.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 6

Applied Concept

A student is asked to identify whether a cross-sectioned ovary belongs to a pea plant or a tomato plant by examining the placentation. How would the student proceed and what differences would they observe?

The student would first count the number of locules (chambers): pea has a unilocular ovary (single chamber) while tomato has a bilocular or multilocular ovary; this immediately distinguishes the two.
In pea (marginal placentation), the ovules are attached to a ridge along the ventral suture of the single-chambered ovary forming two rows; no central axis or septa are present.
In tomato (axile placentation), the ovules are attached to the central axis in a multilocular ovary; the septa divide the ovary into chambers and the central placenta bears ovules in each locule.
This structural difference reflects the carpel number and fusion: pea has a monocarpellary ovary (one carpel, no fusion) giving marginal placentation, while tomato has a bicarpellary syncarpous ovary where fused carpels create the multilocular condition with axile placentation.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 7

Applied Concept

During a field trip, a student finds a plant with flowers where the petals are in a complex arrangement: one large outer petal, two lateral petals, and two small innermost petals fused together. What type of aestivation is this and what does it suggest about the plant's identity and pollination biology?

This is vexillary (papilionaceous) aestivation, a specialised form found in flowers of the subfamily Papilionoideae (family Fabaceae): the largest outer petal is called the standard (vexillum), the two lateral petals are called wings (alae), and the two smallest anterior petals are called the keel (carina) — all overlapping in this specific hierarchy.
This aestivation pattern is characteristic of Fabaceae members like pea (Pisum sativum), bean (Phaseolus), gram (Cicer), and gulmohur (Delonix); the zygomorphic (bilaterally symmetrical) flower associated with this aestivation suggests the plant is from Fabaceae.
The keel petals enclose the stamens and carpel, while the wing petals and standard petal guide bee pollinators; when a bee lands on the wing petals, its weight depresses them, exposing the stamens and carpel for pollen transfer (bee-pollinated landing platform mechanism).
Vexillary aestivation is thus not merely a structural character but is tightly co-evolved with bee pollination; it is a highly reliable diagnostic character for identifying Fabaceae in the field and represents an adaptation for effective cross-pollination.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 8

Applied Concept

A researcher studying mangrove plants observes special roots growing vertically upward out of the mud. With reference to the morphology chapter, identify these roots and explain their functional advantage in the mangrove habitat.

These are pneumatophores (breathing roots) — a type of adventitious root modification found in mangrove plants like Avicennia and Rhizophora that grow in waterlogged, anaerobic (oxygen-deficient) muddy soils.
Pneumatophores grow vertically upward, emerging above the water/mud surface; their outer surface contains numerous pores (lenticels) that allow atmospheric oxygen to diffuse into the root system, overcoming the lack of oxygen in waterlogged soil.
Internally, pneumatophores have large air spaces (aerenchyma) that facilitate the transport of oxygen to the deeply buried submerged roots that cannot access atmospheric oxygen directly.
This modification is an excellent example of adaptive root morphology where the basic anchorage/absorption function is supplemented by a respiratory function necessitated by the unique anaerobic conditions of the mangrove habitat.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 9

Applied Concept

A student dissects a mango and a sunflower. With reference to fruit structure, explain the differences in the position of the ovary that led to the formation of these two different types of fruit.

Mango develops from a hypogynous flower where the ovary is superior (gynoecium is the highest on the thalamus, other floral parts arise below); after fertilisation, only the ovary develops into the true fruit with pericarp differentiated into thin epicarp (outer skin), fleshy mesocarp (edible part), and stony endocarp (the hard 'stone' enclosing the seed).
Sunflower (ray and disc florets) develops from an epigynous flower where the ovary is inferior (thalamus encloses and fuses with the ovary, with other floral parts arising above); the mature fruit (cypsela) therefore has the fused floral tube as part of the fruit wall in addition to the true pericarp.
In mango (drupe), the entire pericarp is derived from the ovary wall alone, giving a clear differentiation of three pericarp layers; in sunflower (cypsela), the pericarp is partly derived from the thalamus fused with the ovary wall.
This illustrates how the position of the ovary at flower stage (hypogynous vs. epigynous) directly determines the structure of the mature fruit, making ovary position a critical character for fruit classification in plant taxonomy.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 10

Applied Concept

A botanist examining a cross-section of a maize kernel under a microscope identifies a distinct protein-rich layer surrounding the starchy endosperm. Name this layer, describe its location, and explain its role during germination.

The protein-rich layer is the aleurone layer — a single layer of cells that forms the outer covering of the endosperm in the maize grain, separating it from the embryo and the seed coat/fruit wall.
During germination, gibberellins produced by the embryo diffuse to the aleurone layer and activate genes encoding hydrolytic enzymes (especially alpha-amylase), which are then secreted into the starchy endosperm.
These enzymes digest the starch and other stored reserves in the endosperm, converting them to soluble sugars and amino acids that are absorbed by the scutellum and transported to the growing embryo axis (plumule and radicle).
The aleurone layer thus acts as a metabolically active signal-receiving and enzyme-secreting tissue that bridges the dormant food store of the endosperm and the growing embryo, making it essential for successful germination and early seedling establishment.

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Chapter 5: Morphology of Flowering Plants | Application Questions

A farmer notices that wheat plants growing in his field have a different root system compared to mustard plants. With reference to the root systems, explain the structural and functional differences and how they relate to the crops' water absorption strategies.

A botanist examines two plants. Plant A has leaves where the leaf base forms a sheath covering the stem, while Plant B has a leaf base bearing two small lateral leaf-like structures. Identify the type of leaf base modification in each case and explain its significance.

With reference to the chapter, a botanist writes the floral formula: ⊕ ♀ K(5) C(5) A5 G(2). Decode this formula and identify the likely plant family it belongs to.

A horticulturist examining two flowers notices that in one flower (X), the petals just touch at the margins without overlapping, while in flower (Y), each petal margin overlaps the next in a consistent direction. Name the aestivation type in each and give examples of plants showing these patterns.

A student is asked to identify whether a cross-sectioned ovary belongs to a pea plant or a tomato plant by examining the placentation. How would the student proceed and what differences would they observe?

A researcher studying mangrove plants observes special roots growing vertically upward out of the mud. With reference to the morphology chapter, identify these roots and explain their functional advantage in the mangrove habitat.

A student dissects a mango and a sunflower. With reference to fruit structure, explain the differences in the position of the ovary that led to the formation of these two different types of fruit.

A botanist examining a cross-section of a maize kernel under a microscope identifies a distinct protein-rich layer surrounding the starchy endosperm. Name this layer, describe its location, and explain its role during germination.

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