Morphology of Flowering Plants
Welcome to HSLC Guru! This article presents a complete English-medium study guide for Class 11 Biology Chapter 5 — Morphology of Flowering Plants, designed strictly to the ASSEB (Assam State School Education Board) syllabus. You will find a clear summary, NCERT-style questions and answers of varying marks, MCQs, fill-in-the-blanks, true/false items and a glossary table to make revision smooth and exam-ready.
Summary
Angiosperms or flowering plants show enormous variation in external form yet share a common ground plan. The plant body is divisible into an underground root system and an aerial shoot system. Roots are of three principal types — tap root (developing from the radicle, characteristic of dicots like mustard and gram), fibrous root (cluster of slender roots arising from the base of the stem, typical of monocots like wheat and grass) and adventitious roots (arising from any part other than the radicle, as in the prop roots of banyan and maize). A typical root tip displays four regions — the root cap, the region of meristematic activity, the region of elongation and the region of maturation bearing root hairs. Roots are modified for storage (carrot, turnip, sweet potato), mechanical support (prop roots of banyan, stilt roots of sugarcane, maize), respiration (pneumatophores of Rhizophora) and other vital functions.
The stem develops from the plumule and bears nodes, internodes, buds, leaves, flowers and fruits. Stems are also modified to suit special needs. Underground stems such as the rhizome of ginger, the tuber of potato, the corm of Colocasia and the bulb of onion store food and aid perennation. Sub-aerial modifications include the runner (grass), stolon (jasmine), offset (Pistia) and sucker (mint) which help in vegetative propagation. Aerial modifications include stem tendrils (cucumber, grapevine), thorns (Citrus, Bougainvillea) and phylloclades (Opuntia, Casuarina) which carry out photosynthesis when leaves are reduced. The leaf is a flattened lateral outgrowth bearing three parts — the leaf base, the petiole and the lamina (blade). The arrangement of veins on the lamina is called venation — reticulate in dicots and parallel in monocots. Leaves are simple when the lamina is undivided and compound (pinnate or palmate) when divided into leaflets. The pattern of leaf attachment on the stem is called phyllotaxy — alternate (sunflower), opposite (guava) and whorled (Alstonia).
The inflorescence is the arrangement of flowers on the floral axis. In a racemose inflorescence the main axis continues to grow and bears flowers laterally in acropetal succession; in a cymose inflorescence the main axis terminates in a flower and further growth proceeds from lateral branches. The flower is the reproductive unit and bears four whorls — calyx (sepals), corolla (petals), androecium (stamens, the male whorl) and gynoecium (carpels, the female whorl). The mode of arrangement of sepals or petals in the floral bud with respect to one another is termed aestivation (valvate, twisted, imbricate, vexillary). The arrangement of ovules within the ovary is called placentation (marginal, axile, parietal, free-central, basal). After fertilisation the ovary develops into a fruit and the ovule into a seed. Fruits may be simple (drupe, berry, pome), aggregate or composite. A dicot seed (e.g., gram) has two cotyledons and is generally non-endospermic, while a monocot seed (e.g., maize) has a single cotyledon (scutellum) and is endospermic.
To describe a flower in standardised form, botanists use the floral formula and floral diagram, which together represent symbols for symmetry, sex, the four whorls and their numbers, fusion and ovary position. The chapter highlights the semi-technical description of three families. Solanaceae (the potato family, e.g., Solanum nigrum) — herbs, shrubs or small trees with alternate leaves; flowers bisexual, actinomorphic; calyx 5, gamosepalous, persistent; corolla 5, gamopetalous; androecium 5, epipetalous; gynoecium bicarpellary, syncarpous, ovary superior, axile placentation; fruit a berry or capsule. Liliaceae (the lily family, e.g., Allium cepa) — monocot herbs with bulbs or rhizomes; flowers bisexual, actinomorphic, trimerous; perianth 3+3, tepals often petaloid; androecium 3+3; gynoecium tricarpellary, syncarpous, ovary superior, axile placentation; fruit capsule or berry. Fabaceae (sub-family Papilionoideae, e.g., Pisum sativum) — herbs, shrubs or trees with pinnately compound leaves and tendrillar leaflets; flowers bisexual, zygomorphic; calyx 5, gamosepalous; corolla 5, papilionaceous with vexillary aestivation; androecium 10, diadelphous (9)+1; gynoecium monocarpellary, ovary superior, marginal placentation; fruit a legume.
Very Short Answer Questions (1 Mark)
Q1. Define morphology.
Answer: Morphology is the study of the external form, structure and various features of plants.
Q2. What is a tap root?
Answer: A tap root is the primary root that develops directly from the radicle and grows vertically downward, bearing lateral branches.
Q3. Name the type of root found in maize.
Answer: Fibrous root system with additional adventitious prop roots.
Q4. Give one example of an underground stem.
Answer: Potato (tuber) or ginger (rhizome).
Q5. What is phyllotaxy?
Answer: Phyllotaxy is the pattern of arrangement of leaves on the stem or branch.
Q6. Define aestivation.
Answer: Aestivation is the mode of arrangement of sepals or petals in a floral bud with respect to other members of the same whorl.
Q7. What is placentation?
Answer: Placentation is the arrangement of ovules within the ovary of a flower.
Q8. Name the family of Pisum sativum.
Answer: Fabaceae (sub-family Papilionoideae).
Q9. What kind of fruit is a legume?
Answer: A dry, dehiscent fruit developing from a monocarpellary, superior ovary and splitting along both sutures.
Q10. Name the type of inflorescence in mustard.
Answer: Racemose (raceme) inflorescence.
Short Answer Questions (2-3 Marks)
Q1. Differentiate between tap root and fibrous root systems.
Answer: A tap root system has a single, prominent primary root developing from the radicle with lateral branches; it is characteristic of dicots (e.g., mustard, mango). A fibrous root system has many slender, equally sized roots arising from the base of the stem, with the primary root being short-lived; it is characteristic of monocots (e.g., wheat, paddy, grass).
Q2. What are the regions of a young root? Mention their functions.
Answer: A typical root tip shows four regions — (i) Root cap: a thimble-like protective covering of the root apex; (ii) Region of meristematic activity: small, thin-walled, actively dividing cells producing new cells; (iii) Region of elongation: cells elongate and enlarge, contributing to root length; (iv) Region of maturation: cells differentiate and mature, bearing fine root hairs that absorb water and minerals from soil.
Q3. Distinguish between simple and compound leaves with examples.
Answer: A simple leaf has a single, undivided lamina or, if incised, the incisions do not reach up to the midrib (e.g., mango, guava). A compound leaf has the lamina divided into several distinct leaflets — pinnately compound when leaflets are arranged on a common rachis (e.g., neem) and palmately compound when leaflets arise from a common point at the tip of the petiole (e.g., silk cotton).
Q4. Differentiate between racemose and cymose inflorescence.
Answer: In a racemose inflorescence the main axis continues to grow indefinitely and flowers are borne laterally in an acropetal succession (older flowers below, younger above), e.g., radish, mustard. In a cymose inflorescence the main axis terminates in a flower and further growth proceeds from one or more lateral branches in basipetal succession, e.g., Solanum, jasmine.
Q5. Define and give an example of each — actinomorphic and zygomorphic flower.
Answer: A flower that can be divided into two equal halves by any vertical plane passing through the centre is called actinomorphic (radially symmetrical), e.g., mustard, Datura, chilli. A flower that can be divided into two equal halves by only one particular vertical plane is called zygomorphic (bilaterally symmetrical), e.g., pea, bean, Cassia.
Q6. Briefly describe types of placentation with one example each.
Answer: (i) Marginal: ovules borne on the ventral suture of a single carpel — pea. (ii) Axile: placenta is axial and ovules are attached in a multilocular ovary — China rose, tomato. (iii) Parietal: ovules develop on the inner wall of a unilocular ovary — mustard. (iv) Free-central: ovules borne on a central axis of a unilocular ovary — Dianthus. (v) Basal: a single ovule attached to the base of the ovary — sunflower.
Long Answer Questions (5-7 Marks)
Q1. Describe the various modifications of stem with suitable examples.
Answer: Stems are modified to perform additional functions besides support and conduction. Underground stem modifications store food and help in perennation — the rhizome of ginger and turmeric, the tuber of potato (with eyes that are nodes bearing axillary buds), the corm of Colocasia and the bulb of onion and garlic. Sub-aerial modifications aid in vegetative propagation — the runner of grass and lawn weeds creeps horizontally; the stolon of jasmine arches and roots at the tip; the offset of Pistia and water hyacinth is a short, thick, horizontal branch; the sucker of mint and chrysanthemum arises underground but emerges obliquely. Aerial modifications serve special needs — stem tendrils of cucumber, watermelon, grapevine and passion flower help in climbing; thorns of Citrus and Bougainvillea protect from grazing animals; phylloclades of Opuntia and Casuarina are flattened or cylindrical green stems performing photosynthesis when leaves are reduced to spines or scales to reduce transpiration in xerophytes; the cladode is a one-internode-long phylloclade as in Asparagus.
Q2. Describe the parts of a typical flower with the help of a labelled diagram.
Answer: A typical flower is the modified shoot meant for sexual reproduction. It is borne on a stalk called the pedicel which expands at the tip into the thalamus or receptacle. Four whorls are arranged on the thalamus. (i) Calyx: outermost whorl made of green sepals; protects the bud and may be polysepalous (free) or gamosepalous (united). (ii) Corolla: composed of brightly coloured petals that attract pollinators; may be polypetalous or gamopetalous and may show valvate, twisted, imbricate or vexillary aestivation. (iii) Androecium: the male whorl made of stamens; each stamen has a filament and a bilobed anther where pollen grains are produced; stamens may be free, monoadelphous, diadelphous or polyadelphous. (iv) Gynoecium: the female whorl composed of one or more carpels; each carpel has a basal ovary, a slender style and a sticky stigma; the ovary contains ovules attached to the placenta. On the basis of position of ovary the flower may be hypogynous (superior ovary), perigynous or epigynous (inferior ovary).
Q3. Give a semi-technical description of a typical flower of family Solanaceae with floral formula and floral diagram.
Answer: Solanaceae — the potato or nightshade family, with examples such as Solanum nigrum, Solanum tuberosum and Datura. Habit: herbs, shrubs and small trees, often bearing bicollateral vascular bundles. Stem: aerial, erect, cylindrical, branched, solid or hollow, hairy. Leaves: alternate, simple, exstipulate, with reticulate venation. Inflorescence: solitary, axillary or cymose. Flower: bisexual, actinomorphic, pentamerous, hypogynous, with bracts. Calyx: 5 sepals, gamosepalous, persistent, valvate aestivation. Corolla: 5 petals, gamopetalous, valvate aestivation. Androecium: 5 stamens, polyandrous, epipetalous. Gynoecium: bicarpellary, syncarpous, ovary superior, bilocular, placenta swollen with many ovules on axile placentation; carpels are placed obliquely. Fruit: berry (tomato) or capsule (Datura). Seeds: many, endospermic. Floral formula: Br ⊕ ⚥ K(5) C(5) A5 G(2). The family is economically important — food (potato, tomato, brinjal), spice (chilli), medicine (Atropa, Withania) and ornamentals (Petunia).
Q4. Give a semi-technical description of family Fabaceae (Papilionoideae) with reference to Pisum sativum.
Answer: Fabaceae (Papilionoideae) — the pea family. Habit: trees, shrubs, herbs; root with characteristic nitrogen-fixing nodules. Stem: erect or climbing. Leaves: alternate, pinnately compound or simple, leaf base pulvinate, stipulate, venation reticulate; the upper leaflets in pea are modified into tendrils. Inflorescence: racemose. Flower: bisexual, zygomorphic. Calyx: 5 sepals, gamosepalous, imbricate aestivation. Corolla: 5 petals, polypetalous, papilionaceous comprising one posterior standard (vexillum), two lateral wings and two anterior fused petals forming a keel; aestivation vexillary. Androecium: 10 stamens, diadelphous (9 fused + 1 free), anthers dithecous. Gynoecium: monocarpellary, ovary superior, unilocular with many ovules, marginal placentation; style single, bent. Fruit: legume (pod). Seed: one to many, non-endospermic. Floral formula: Br % ⚥ K(5) C1+2+(2) A(9)+1 G1. The family yields pulses (gram, arhar, pea), edible oil (soybean, groundnut), dye (Indigofera), fibre (Crotalaria) and medicines.
Q5. Compare the structure of monocot and dicot seeds taking maize and gram as examples.
Answer: A dicot seed like gram is enclosed within the seed coat made of an outer testa and an inner tegmen; a scar called the hilum represents the point of attachment to the fruit; below it lies a small pore, the micropyle. Inside the seed coat lies the embryo consisting of two fleshy cotyledons that store food, and an embryonal axis with the radicle at one end and plumule at the other; gram is non-endospermic since food is stored in the cotyledons, while castor is endospermic. A monocot seed like maize (technically a one-seeded fruit, the caryopsis) has a fused seed coat and fruit wall. The endosperm forms the bulk of the seed and stores food; it is separated from the embryo by a proteinaceous layer called the aleurone layer. The embryo lies on one side and consists of a single shield-shaped cotyledon, the scutellum, an embryonal axis with a plumule enclosed in a coleoptile and a radicle enclosed in a coleorhiza. Thus monocot seeds are typically endospermic with one cotyledon, whereas dicot seeds are usually non-endospermic with two cotyledons.
Multiple Choice Questions (MCQs)
Q1. The edible part of potato is a:
(a) Root (b) Stem tuber (c) Bulb (d) Corm
Answer: (b) Stem tuber.
Q2. Pneumatophores are seen in:
(a) Carrot (b) Banyan (c) Rhizophora (d) Maize
Answer: (c) Rhizophora.
Q3. Reticulate venation is a characteristic of:
(a) Monocot leaf (b) Dicot leaf (c) Gymnosperm leaf (d) Fern leaf
Answer: (b) Dicot leaf.
Q4. The fruit of pea is a:
(a) Berry (b) Drupe (c) Legume (d) Capsule
Answer: (c) Legume.
Q5. Aestivation found in pea flower is:
(a) Valvate (b) Twisted (c) Imbricate (d) Vexillary
Answer: (d) Vexillary.
Q6. Placentation in tomato is:
(a) Marginal (b) Parietal (c) Axile (d) Free-central
Answer: (c) Axile.
Q7. Onion is a modified:
(a) Stem (bulb) (b) Root (c) Leaf (d) Fruit
Answer: (a) Stem (bulb).
Q8. A flower with both male and female reproductive organs is:
(a) Unisexual (b) Bisexual (c) Sterile (d) Asexual
Answer: (b) Bisexual.
Q9. The number of stamens in a typical Liliaceae flower is:
(a) 4 (b) 5 (c) 6 (d) 10
Answer: (c) 6 (in two whorls of three).
Q10. Stilt roots are seen in:
(a) Carrot (b) Sugarcane (c) Mustard (d) Wheat
Answer: (b) Sugarcane.
Fill in the Blanks
Q1. The protective covering at the tip of the root is called the __________.
Answer: root cap.
Q2. The arrangement of leaves on a stem is known as __________.
Answer: phyllotaxy.
Q3. The female reproductive whorl of a flower is the __________.
Answer: gynoecium.
Q4. The fruit of mango is a __________.
Answer: drupe.
Q5. In maize seed, the radicle is enclosed by a sheath called __________.
Answer: coleorhiza.
True or False
Q1. Ginger is a modified root.
Answer: False (ginger is a modified underground stem — rhizome).
Q2. Sunflower has a racemose head inflorescence (capitulum).
Answer: True.
Q3. The flower of pea is actinomorphic.
Answer: False (it is zygomorphic).
Q4. Onion is a bulb showing modification of stem.
Answer: True.
Q5. Aleurone layer is found in dicot seeds.
Answer: False (it is found in monocot seeds like maize).
Glossary
| Term | Meaning |
|---|---|
| Radicle | Embryonic root that gives rise to the tap root system. |
| Plumule | Embryonic shoot that develops into the stem and leaves. |
| Adventitious root | Root that arises from any plant part other than the radicle. |
| Pneumatophore | Negatively geotropic respiratory root in mangroves. |
| Rhizome | Underground stem growing horizontally with nodes and scale leaves (e.g., ginger). |
| Phylloclade | Green, flattened or cylindrical photosynthetic stem (e.g., Opuntia). |
| Petiole | Stalk that attaches the leaf blade to the stem. |
| Lamina | The expanded green photosynthetic blade of a leaf. |
| Reticulate venation | Network-like vein pattern typical of dicot leaves. |
| Parallel venation | Veins running parallel to one another in monocot leaves. |
| Phyllotaxy | Arrangement of leaves on a stem (alternate, opposite, whorled). |
| Inflorescence | Mode of arrangement of flowers on the floral axis. |
| Aestivation | Mode of arrangement of sepals/petals in a floral bud. |
| Placentation | Arrangement of ovules on the placenta within the ovary. |
| Calyx | Outermost whorl of a flower made of sepals. |
| Corolla | Whorl of petals, often coloured to attract pollinators. |
| Androecium | Male reproductive whorl of stamens in a flower. |
| Gynoecium | Female reproductive whorl made of one or more carpels. |
| Vexillary | Aestivation in pea where the largest petal overlaps two lateral wings. |
| Diadelphous | Stamens fused into two bundles, as in pea (9+1). |
| Legume | Dry dehiscent fruit splitting along both sutures (e.g., pea pod). |
| Drupe | One-seeded fleshy fruit with a hard endocarp (e.g., mango). |
| Berry | Fleshy fruit with seeds embedded in pulp (e.g., tomato, brinjal). |
| Scutellum | Shield-shaped single cotyledon of a monocot seed (e.g., maize). |
| Coleoptile | Protective sheath around the plumule in monocot seeds. |
| Coleorhiza | Protective sheath around the radicle in monocot seeds. |
| Aleurone layer | Outermost proteinaceous layer of the endosperm in maize. |
| Floral formula | Symbolic representation of a flower’s structure. |
| Actinomorphic | Radially symmetrical flower (e.g., mustard, Datura). |
| Zygomorphic | Bilaterally symmetrical flower (e.g., pea, Cassia). |