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These are complete NCERT Solutions for CBSE Class 11 Biology Chapter 5 — Morphology of Flowering Plants. Attempt each question before checking. For morphology questions, use correct terminology — marks are given for terms like 'internode', 'axil', 'racemose', 'cymose', 'placentation', etc.
Key Concepts (Quick Recap)
- Root systems: Taproot (dicots) vs Fibrous root (monocots); root regions: root cap, region of meristematic activity, elongation, maturation.
- Stem modifications: Tendril (cucumber), thorn (citrus), phylloclade (Opuntia), rhizome (ginger), tuber (potato), bulb (onion).
- Leaf: Stipules, petiole, lamina; venation — parallel (monocots) vs reticulate (dicots); phyllotaxis — alternate, opposite, whorled.
- Inflorescence: Racemose (indefinite growth) vs Cymose (definite growth).
- Flower: Calyx, corolla, androecium, gynoecium; actinomorphic vs zygomorphic; unisexual vs bisexual.
- Fruit: Pericarp (epicarp + mesocarp + endocarp); true fruit (from ovary) vs false fruit (from other floral parts).
- Seed: Dicot (two cotyledons) vs Monocot (one cotyledon, endospermic); seed coat, embryo, endosperm.
- Families: Fabaceae (Leguminosae), Solanaceae, Liliaceae — distinctive features.
Intext Questions
Page 67
Q1. What is meant by modification of root? What type of modification of root is found in the: (a) Banyan tree (b) Turnip (c) Mangrove trees
Answer
Modification of root means roots changing their normal structure to perform functions other than absorption and anchorage — such as storage, support, and respiration.
(a) Banyan tree — Prop roots (Stilt roots): Roots arise from branches, grow downward, enter soil, and provide additional support to the massive tree canopy.
(b) Turnip — Tuberous roots (Storage roots): The taproot becomes swollen and fleshy due to storage of food (starch). Similar modifications are seen in radish, carrot, and sweet potato.
(c) Mangrove trees — Pneumatophores (Respiratory roots): Roots grow vertically upward from the soil surface to obtain oxygen for respiration, as the waterlogged soil lacks air. These roots have pores (pneumathodes) for gas exchange.
Q2. Justify the following statements on the basis of external features: (i) Underground parts of a plant are not always roots. (ii) Flower is a modified shoot.
Answer
(i) Underground parts are not always roots: Many plants have underground stems that are modified for storage, perennation, or vegetative propagation. Examples: Potato tuber (modified stem — has nodes, eyes/buds), ginger rhizome (modified stem — has nodes, internodes, and scale leaves), onion bulb (modified stem — has fleshy leaf bases and a disc-like stem). These can be distinguished from roots by the presence of nodes, internodes, and buds.
(ii) Flower is a modified shoot: A flower develops from a floral bud on the stem. The thalamus (receptacle) is the modified stem tip, and the floral parts (sepals, petals, stamens, carpels) are modified leaves arranged in whorls on the thalamus. The position of floral parts on the thalamus corresponds to the arrangement of leaves on a stem, confirming the flower is a modified shoot.
Page 74
Q1. How is a pinnately compound leaf different from a palmately compound leaf?
Answer
| Feature | Pinnately Compound Leaf | Palmately Compound Leaf |
|---|
| Leaflets arranged | Along both sides of a common axis (rachis), like a feather | All leaflets attached at a single point at the tip of the petiole, like fingers of a palm |
| Rachis | Present (the main axis) | Absent |
| Examples | Neem, Rose, Tamarind | Silk cotton, Bombax, Oxalis |
Q2. How do the leaf modifications in pitcher plant help the plant?
Answer
In the pitcher plant (Nepenthes), the leaf is modified into a pitcher to trap insects. The leaf tip forms a pitcher-like structure filled with water and digestive enzymes. The rim of the pitcher is slippery, and insects that land on it fall inside. The lid-like structure above prevents rainwater from diluting the digestive enzymes. The trapped insects are digested, and the plant absorbs the nitrogen and minerals — this is an adaptation to nitrogen-poor soil habitats.
Chapter-End Exercise
Q1. What is meant by modification of root? What type of modification of root is found in the: (a) Banyan tree (b) Turnip (c) Mangrove trees
Answer
(See Intext Page 67 Q1 — answered above.)
Q2. Justify the following statements on the basis of external features: (i) Underground parts of a plant are not always roots. (ii) Flower is a modified shoot.
Answer
(See Intext Page 67 Q2 — answered above.)
Q3. Take one flower each of the families Fabaceae and Solanaceae and write its floral formula. Also draw the floral diagram.
Answer
*Fabaceae (e.g., Pea — Pisum sativum):*
- Floral formula: % ⚥ K₅ C₁+₂+(2) A₁+(9) G₁
- % = zygomorphic, ⚥ = bisexual
- K₅ = Calyx 5 sepals, united
- C₁+₂+(2) = Corolla — 1 standard, 2 wings, 2 keel (papilionaceous)
- A₁+(9) = Androecium — 1 free stamen + 9 fused (diadelphous)
- G₁ = Gynoecium — 1 carpel, superior ovary, unilocular
Solanaceae (e.g., Datura / Brinjal):
- Floral formula: ⚹ ⚥ K₅ C₅ A₅ G₂
- ⚹ = actinomorphic, ⚥ = bisexual
- K₅ = Calyx 5 sepals, united (gamosepalous)
- C₅ = Corolla 5 petals, united (gamopetalous)
- A₅ = Androecium 5 stamens, epipetalous
- G₂ = Gynoecium 2 carpels, syncarpous, superior ovary, bilocular
(Floral diagrams should be drawn as per NCERT Fig 5.19 and 5.20 — showing the relative position, union, and number of each whorl.)
Q4. Describe the arrangement of floral members in relation to their insertion on thalamus.
Answer
Based on the position of floral parts on the thalamus relative to the ovary:
1. Hypogynous (Superior ovary): Ovary is the highest point on the thalamus; sepals, petals, and stamens arise below the ovary. Example: Mustard, China rose, brinjal. 2. Perigynous (Half-inferior ovary): Ovary is in the centre; other floral parts are at the rim of the cup-shaped thalamus at the same level. Example: Rose, peach, plum. 3. Epigynous (Inferior ovary): Ovary is embedded in the thalamus; sepals, petals, and stamens arise above the ovary. Example: Sunflower, cucumber, guava.
Q5. Define the following terms: (i) Aestivation (ii) Placentation (iii) Actinomorphic (iv) Zygomorphic (v) Superior ovary
Answer
1. Aestivation: The arrangement of sepals or petals in a floral bud with respect to each other. Types: valvate, twisted, imbricate, vexillary (papilionaceous). 2. Placentation: The arrangement of ovules inside the ovary. Types: marginal, axile, parietal, basal, central, free-central. 3. Actinomorphic: A flower that can be divided into two equal halves by any vertical plane passing through the centre — radially symmetrical. Example: Mustard, Datura. 4. Zygomorphic: A flower that can be divided into two similar halves only in one vertical plane — bilaterally symmetrical. Example: Pea, Bean, Cassia. 5. Superior ovary: When the ovary is positioned above the other floral parts on the thalamus (hypogynous condition). Example: Mustard, China rose.
Q6. Differentiate between: (a) Racemose and Cymose inflorescence (b) Fibrous root and Adventitious root (c) Apocarpous and Syncarpous ovary
Answer
(a) Racemose vs Cymose Inflorescence:
| Feature | Racemose | Cymose |
|---|
| Main axis | Continues to grow (indeterminate) | Terminates in a flower (determinate) |
| Flower arrangement | Acropetal (youngest at tip) | Basipetal (oldest at tip) |
| Number of flowers | Can be unlimited | Limited |
| Examples | Raceme, spike, catkin, corymb | Solitary, cyme, biparous cyme |
(b) Fibrous Root vs Adventitious Root:
| Feature | Fibrous Root | Adventitious Root |
|---|
| Origin | From the base of the stem (replacing the primary root) | From any part of the plant other than the radicle |
| Examples | Wheat, rice, maize | Banyan prop roots, screw pine stilt roots, grass |
| Function | Absorption and anchorage | Support, respiration, storage, or absorption |
(c) Apocarpous vs Syncarpous Ovary:
| Feature | Apocarpous | Syncarpous |
|---|
| Carpels | Free (not fused) | Fused together |
| Ovaries | Separate ovaries | Single compound ovary |
| Examples | Lotus, Rose (some species) | Mustard, Tomato, Datura |
Q7. Write the floral formula of a actinomorphic, bisexual, hypogynous flower with 5 united sepals, 5 free petals, 5 free stamens and 3 united carpels, superior ovary, axile placentation.
Answer
Floral formula: ⚹ ⚥ K₅ C₅ A₅ G(₃)
Where:
- ⚹ = actinomorphic (radially symmetrical)
- ⚥ = bisexual
- K₅ = 5 united sepals (gamosepalous)
- C₅ = 5 free petals (polypetalous)
- A₅ = 5 free stamens (polyandrous)
- G(₃) = 3 united carpels (syncarpous), superior ovary (hypogynous)
- Placentation: axile (ovules attached to the central axis in a multilocular ovary)
Q8. Describe the arrangement of floral members in Solanaceae and Fabaceae.
Answer
Solanaceae: ⚹ ⚥ K₅ C₅ A₅ G₂ — Actinomorphic, bisexual, hypogynous; 5 united sepals (gamosepalous), 5 united petals (gamopetalous), 5 stamens epipetalous, 2 carpels syncarpous, superior ovary, axile placentation.
Fabaceae: % ⚥ K₅ C₁+₂+(2) A₁+(9) G₁ — Zygomorphic, bisexual, hypogynous; 5 united sepals, papilionaceous corolla (1 standard + 2 wings + 2 keel), diadelphous stamens (1+9), 1 carpel, superior ovary, marginal placentation.
Internal Links
- [Chapter 5 Guide — Morphology of Flowering Plants](/school/cbse/class/11/biology/cbse-morphology-of-flowering-plants)
- [All Class 11 Biology Solutions](/school/cbse/class/11/biology/solutions)
- [Class 11 Biology Subject Guide](/school/cbse/class/11/biology)
