NCERT Solutions for Class 11 Biology Chapter 5: Morphology of Flowering Plants
All 10 exercise questions of the latest NCERT textbook (2026–27 reprint) answered with exam-ready descriptive detail — compound leaves, phyllotaxy, floral terms, inflorescence, seeds, the Solanaceae description with floral diagram, placentation, flower parts and thalamus position — with 17 labelled diagrams linked to the exact NCERT pages, comparison tables, flow charts, complete revision notes covering every section of the chapter, and exam tips.
Chapter at a glance — complete revision notes
Unit 2 and chapter introduction
- Unit 2 – Structural Organisation in Plants and Animals. Description of the diverse forms of life was first made only by observation — with naked eyes, later with magnifying lenses and microscopes — mainly of gross structural features, external and internal. Before experimental biology or physiology was established, naturalists only described biology, so biology long remained natural history. This description later became meaningful in the reductionist biology where living processes drew more attention, and helped in framing research questions in physiology and evolutionary biology. Chapters of the unit: 5 Morphology of Flowering Plants, 6 Anatomy of Flowering Plants, 7 Structural Organisation in Animals.
- Katherine Esau (1898–1997) — born in Ukraine in 1898; studied agriculture in Russia and Germany; doctorate in USA (1931). Showed that the curly top virus spreads through the phloem. Her Plant Anatomy (1954) took a dynamic, developmental approach and revived the discipline; The Anatomy of Seed Plants (1960) was called the “Webster’s of plant biology”. Elected to the National Academy of Sciences in 1957 (sixth woman); received the National Medal of Science (1989). Peter Raven recalled that she “absolutely dominated” plant biology even at 99.
- Angiosperms show a large diversity in morphology but all have roots, stems, leaves, flowers and fruits. For classification and understanding any higher plant we need standard technical terms and definitions and the possible variations found as adaptations (to habitats, protection, climbing, storage, etc.). The underground part is the root system and the part above ground is the shoot system.
5.1 The Root
- In most dicots the direct elongation of the radicle forms the primary root, which grows in the soil and bears lateral roots of several orders (secondary, tertiary…). The primary root and its branches form the tap root system (e.g., mustard).
- In monocots the primary root is short-lived and is replaced by many roots arising from the base of the stem — the fibrous root system (e.g., wheat).
- In some plants (grass, Monstera, banyan tree) roots arise from parts of the plant other than the radicle — adventitious roots.
- Functions: absorption of water and minerals from the soil, anchorage, storage of reserve food material and synthesis of plant growth regulators.
5.1.1 Regions of the root
- Root cap — thimble-like structure at the apex that protects the tender apex as it moves through the soil.
- Region of meristematic activity — a few mm above the cap; cells are very small, thin-walled with dense protoplasm and divide repeatedly.
- Region of elongation — cells proximal to the meristem undergo rapid elongation and enlargement, responsible for growth of the root in length.
- Region of maturation — cells of the elongation zone gradually differentiate and mature; some epidermal cells form fine, delicate thread-like root hairs that absorb water and minerals from the soil.
5.2 The Stem
- The stem is the ascending part of the axis bearing branches, leaves, flowers and fruits; it develops from the plumule of the embryo. It bears nodes (where leaves are borne) and internodes (portions between two nodes) and buds (terminal or axillary). It is generally green when young and later often woody and dark brown.
- Functions: spreading out branches bearing leaves, flowers and fruits; conducting water, minerals and photosynthates; some stems also store food, give support, protection and help in vegetative propagation.
5.3 The Leaf
- A leaf is a lateral, generally flattened structure borne on the stem; it develops at the node and bears a bud in its axil (axillary bud, which later develops into a branch). Leaves originate from shoot apical meristems and are arranged in acropetal order; they are the most important vegetative organs for photosynthesis.
- A typical leaf has leaf base, petiole and lamina (Fig. 5.4a). The leaf base attaches the leaf to the stem and may bear two lateral small leaf-like stipules; in monocots it expands into a sheath covering the stem; in some leguminous plants it is swollen — the pulvinus. The petiole holds the blade to light; long thin flexible petioles let the blade flutter in wind, cooling the leaf and bringing fresh air. The lamina is the green expanded part with veins and veinlets and a prominent midrib; veins give rigidity and transport water, minerals and food. Shape, margin, apex, surface and extent of incision vary.
5.3.1 Venation
- Venation = arrangement of veins and veinlets in the lamina. Reticulate – veinlets form a network (generally dicots; Fig. 5.4b). Parallel – veins run parallel (most monocots; Fig. 5.4c).
5.3.2 Types of leaves
- Simple leaf – lamina entire or incised, incisions not reaching the midrib. Compound leaf – incisions reach the midrib, breaking the lamina into leaflets. A bud is in the axil of the petiole in both, but not in the axil of leaflets. Pinnately compound – leaflets on a common axis, the rachis (midrib), as in neem. Palmately compound – leaflets attached at a common point, the tip of the petiole, as in silk cotton (Fig. 5.5).
5.3.3 Phyllotaxy
- Pattern of arrangement of leaves on the stem or branch (Fig. 5.6): alternate (single leaf at each node – china rose, mustard, sunflower); opposite (pair at each node – Calotropis, guava); whorled (more than two leaves at a node – Alstonia).
5.4 The Inflorescence
- A flower is a modified shoot: the shoot apical meristem changes to floral meristem, internodes do not elongate, the axis is condensed, and the apex produces floral appendages laterally at successive nodes instead of leaves. When a shoot tip transforms into a flower it is always solitary. Inflorescence = arrangement of flowers on the floral axis.
- Racemose – main axis continues to grow; flowers borne laterally in acropetal succession (Fig. 5.7). Cymose – main axis terminates in a flower, hence limited growth; flowers in basipetal order (Fig. 5.8).
5.5 The Flower
- The flower is the reproductive unit of angiosperms, meant for sexual reproduction. A typical flower has four whorls on the swollen end of the stalk (pedicel), the thalamus / receptacle: calyx, corolla, androecium, gynoecium. Calyx and corolla = accessory organs; androecium and gynoecium = reproductive organs. In lily the calyx and corolla are not distinct – perianth. Bisexual flower has both androecium and gynoecium; unisexual has only stamens or only carpels.
- Symmetry: actinomorphic (radial; divisible into two equal radial halves in any radial plane – mustard, datura, chilli), zygomorphic (bilateral; only one vertical plane – pea, gulmohur, bean, Cassia), asymmetric (irregular – canna).
- Flowers are trimerous, tetramerous or pentamerous when floral appendages are in multiples of 3, 4 or 5; bracteate (with bracts – reduced leaves at the base of the pedicel) or ebracteate.
- Position of floral parts on the thalamus (Fig. 5.9): Hypogynous – gynoecium highest, other parts below; ovary superior (mustard, china rose, brinjal). Perigynous – gynoecium in the centre, other parts on the rim of the thalamus at about the same level; ovary half inferior (plum, rose, peach). Epigynous – margin of thalamus grows up enclosing the ovary completely and fusing with it; other parts arise above; ovary inferior (guava, cucumber, ray florets of sunflower).
5.5.1 Parts of a flower
- Calyx – outermost whorl of sepals; usually green and leaf-like, protecting the flower in the bud stage; gamosepalous (united) or polysepalous (free).
- Corolla – composed of petals, brightly coloured to attract insects for pollination; gamopetalous or polypetalous; may be tubular, bell-shaped, funnel-shaped or wheel-shaped.
- Aestivation – mode of arrangement of sepals or petals in the floral bud (Fig. 5.11): valvate (just touch at the margin, no overlap – Calotropis); twisted (one margin overlaps the next – china rose, lady’s finger, cotton); imbricate (overlap not in any particular direction – Cassia, gulmohur); vexillary / papilionaceous (pea, bean: largest petal standard overlaps two lateral wings which overlap two smallest anterior petals, the keel).
- Androecium – composed of stamens (male reproductive organ): filament + anther; each anther is bilobed, each lobe with two chambers, the pollen-sacs producing pollen grains. A sterile stamen = staminode. Stamens may be attached to petals (epipetalous – brinjal) or to the perianth (epiphyllous – lily); free (polyandrous) or united: one bundle monoadelphous (china rose), two bundles diadelphous (pea), more than two polyadelphous (citrus). Filament length may vary within a flower (Salvia, mustard).
- Gynoecium – female reproductive part made of one or more carpels; a carpel has stigma (receptive surface for pollen), style (elongated tube) and ovary (enlarged basal part) bearing one or more ovules on a cushion-like placenta. Carpels free = apocarpous (lotus, rose); fused = syncarpous (mustard, tomato). After fertilisation ovules → seeds, ovary → fruit.
- Placentation – arrangement of ovules within the ovary (Fig. 5.12): marginal (placenta forms a ridge along the ventral suture, ovules in two rows – pea); axile (placenta axial, multilocular ovary – china rose, tomato, lemon); parietal (ovules on the inner wall; one chamber made two by a false septum – mustard, Argemone); free central (ovules on central axis, no septa – Dianthus, primrose); basal (placenta at the base, single ovule – sunflower, marigold).
5.6 The Fruit
- The fruit is a mature or ripened ovary developed after fertilisation, a characteristic feature of flowering plants. A fruit formed without fertilisation is parthenocarpic. It consists of a pericarp (wall; dry or fleshy) and seeds; a thick fleshy pericarp is differentiated into outer epicarp, middle mesocarp and inner endocarp.
- Drupe – mango and coconut; develops from monocarpellary superior ovaries and is one-seeded (Fig. 5.13). Mango: thin epicarp, fleshy edible mesocarp, stony hard endocarp. Coconut: fibrous mesocarp.
5.7 The Seed
- Ovules after fertilisation develop into seeds. A seed = seed coat + embryo; the embryo has a radicle, embryonal axis and one cotyledon (wheat, maize) or two cotyledons (gram, pea).
- Dicotyledonous seed (Fig. 5.14): seed coat of outer testa and inner tegmen; hilum = scar where the seed was attached to the fruit; micropyle = small pore above the hilum; embryo = embryonal axis + two cotyledons (often fleshy with reserve food); radicle and plumule at the two ends of the axis. Endospermic seeds (e.g., castor) retain the endosperm formed by double fertilisation; non-endospermous (bean, gram, pea) lose it.
- Monocotyledonous seed (Fig. 5.15): usually endospermic (some, e.g., orchids, non-endospermic). In cereals like maize the seed coat is membranous and fused with the fruit wall; endosperm bulky; the aleurone layer (proteinous) separates endosperm from the embryo; embryo small, in a groove at one end, with one large shield-shaped cotyledon, the scutellum, and a short axis with plumule and radicle enclosed in sheaths coleoptile and coleorhiza.
5.8 Semi-technical description of a typical flowering plant
- The description is brief, in simple scientific language, in proper sequence: habit → vegetative characters (roots, stem, leaves) → floral characters (inflorescence, flower parts) → floral diagram and floral formula.
- Floral formula symbols: Br = bracteate; K = calyx; C = corolla; P = perianth; A = androecium; G = gynoecium (G underlined = superior ovary, G with a line above = inferior ovary); ♂ male; ♀ female; ⚥ bisexual; ⊕ actinomorphic; % zygomorphic. Fusion is shown by enclosing the figure in brackets; adhesion by a line drawn above the symbols.
- A floral diagram gives the number of parts, their arrangement and mutual relations; the mother axis is shown by a dot at the top; calyx, corolla, androecium, gynoecium drawn in successive whorls (calyx outermost, gynoecium in the centre). The diagram and formula in Fig. 5.16 represent mustard (Brassicaceae): ⊕ ⚥ K2+2 C4 A2+4 G(2).
5.9 Solanaceae – the “potato family”
- Large family; widely distributed in tropics, subtropics and temperate zones (Fig. 5.17, Solanum nigrum – makoi).
- Vegetative: mostly herbs, shrubs, rarely small trees; stem herbaceous, rarely woody, aerial, erect, cylindrical, branched, solid or hollow, hairy or glabrous; underground stem in potato (Solanum tuberosum); leaves alternate, simple, rarely pinnately compound, exstipulate, reticulate venation.
- Floral: inflorescence solitary, axillary or cymose (Solanum); flower bisexual, actinomorphic; calyx 5 sepals, united, persistent, valvate; corolla 5 petals, united, valvate; androecium 5 stamens, epipetalous; gynoecium bicarpellary, obliquely placed, syncarpous, ovary superior, bilocular, placenta swollen with many ovules, axile; fruit berry or capsule; seeds many, endospermous. Floral formula: ⊕ ⚥ K(5) C(5) A5 G(2) (stamens adhere to the corolla).
- Economic importance: food – tomato, brinjal, potato; spice – chilli; medicine – belladonna, ashwagandha; fumigatory – tobacco; ornamental – petunia.
Summary (as in NCERT)
- Flowering plants show enormous variation in shape, size, structure, nutrition, life span, habit and habitat. Dicots generally have tap roots, monocots fibrous roots; roots may be modified for storage, support and respiration. The shoot system = stem, leaves, flowers, fruits. Stems are distinguished from roots by nodes and internodes, multicellular hair and positive phototropism. The leaf is a lateral outgrowth of the stem developed exogenously at the node. The flower is a modified shoot; after fertilisation ovary → fruit and ovules → seeds; seeds may be monocot or dicot. Floral characteristics form the basis of classification and identification of flowering plants, illustrated through semi-technical descriptions, floral diagrams and floral formulae.
How is a pinnately compound leaf different from a palmately compound leaf?
Concept. A leaf is simple when its lamina is entire or, if incised, the incisions do not touch the midrib. When the incisions of the lamina reach up to the midrib, breaking it into a number of leaflets, the leaf is compound. A bud is present in the axil of the petiole in both simple and compound leaves, but not in the axil of the leaflets of a compound leaf — this helps to distinguish a leaflet from a leaf. Compound leaves are of two types: pinnately compound and palmately compound (Fig. 5.5).
Pinnately compound leaf. A number of leaflets are present on a common axis called the rachis, which represents the midrib of the leaf. The leaflets are arranged along the rachis, usually in pairs, like the barbs of a feather (pinna = feather). Example (NCERT): neem.
Palmately compound leaf. The leaflets are attached at a common point, i.e., at the tip of the petiole, and spread out like the fingers of a palm (palma = palm of the hand); there is no rachis. Example (NCERT): silk cotton.
| Basis | Pinnately compound leaf | Palmately compound leaf |
|---|---|---|
| Arrangement of leaflets | Leaflets arranged along a common axis (rachis) | Leaflets attached at a common point — the tip of the petiole |
| Rachis | Present — it represents the midrib of the leaf | Absent (the petiole ends where leaflets arise) |
| Resemblance | Feather-like (pinna = feather) | Palm-like / hand-like |
| Axillary bud | At the axil of the petiole, not at the axil of leaflets | At the axil of the petiole, not at the axil of leaflets |
| Incisions of the lamina | Reach the midrib; leaflets along it | Reach the tip of the petiole; leaflets radiate from it |
| Examples | Neem (NCERT); also rose, tamarind (standard) | Silk cotton (NCERT); also Cannabis (standard) |
Extra depth — leaf or leaflet? To decide whether a structure is a whole leaf or a leaflet, look for the axillary bud. A true leaf (simple or compound) has a bud in the axil of its petiole; a leaflet of a compound leaf has no bud in its axil. A pinnately compound leaf can look like a twig with simple leaves, but the twig would have buds in the axils of each of its leaves, while the rachis does not.
Conclusion: in a pinnately compound leaf (e.g., neem) the leaflets are borne on a common axis, the rachis, which represents the midrib, whereas in a palmately compound leaf (e.g., silk cotton) the leaflets are attached at one common point at the tip of the petiole.
Explain with suitable examples the different types of phyllotaxy.
Concept. Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. Leaves arise at the nodes; the number of leaves at a node decides the type. Phyllotaxy is usually of three types — alternate, opposite and whorled (Fig. 5.6). A regular arrangement ensures that every leaf receives maximum sunlight for photosynthesis and is not shaded by the leaf above it.
- Alternate phyllotaxy. A single leaf arises at each node in an alternate manner, i.e., successive leaves are on opposite sides of the stem and at different levels. Examples (NCERT): China rose (Hibiscus), mustard and sunflower.
- Opposite phyllotaxy. A pair of leaves arises at each node and lie opposite to each other. Examples (NCERT): Calotropis and guava. (In Calotropis successive pairs lie in the same plane — opposite superposed — while in guava each pair is at right angles to the one below — opposite decussate; this refinement is standard knowledge.)
- Whorled phyllotaxy. More than two leaves arise at a node and form a whorl around the stem. Example (NCERT): Alstonia (devil tree); also Nerium (oleander) in some cases.
| Type | Number of leaves at a node | Arrangement | Examples (NCERT) |
|---|---|---|---|
| Alternate | One | Leaves arise singly, in alternate manner on opposite sides | China rose, mustard, sunflower |
| Opposite | Two (a pair) | The two leaves lie opposite each other | Calotropis, guava |
| Whorled | More than two | Leaves form a whorl round the node | Alstonia |
Extra depth. Phyllotaxy is a morphological character used in identifying plants and families; for example, Solanaceae (Solanum) leaves are alternate and simple (Section 5.9), while guava and Calotropis have opposite leaves. It is related to the principle that leaves develop from the shoot apical meristem in an acropetal order at the nodes.
Conclusion: phyllotaxy is of three types — alternate (one leaf per node: China rose, mustard, sunflower), opposite (a pair of leaves per node: Calotropis, guava) and whorled (more than two leaves per node: Alstonia).
Define the following terms: (a) aestivation (b) placentation (c) actinomorphic (d) zygomorphic (e) superior ovary (f) perigynous flower (g) epipetalous stamen
Concept. These are basic descriptive terms used in the semi-technical description of a flower (Section 5.8). Each is defined below with its NCERT examples.
(a) Aestivation. The mode of arrangement of sepals or petals in a floral bud with respect to the other members of the same whorl. The main types (Fig. 5.11) are valvate (margins just touch without overlapping – Calotropis), twisted (one margin overlaps the next, all in one direction – China rose, lady’s finger, cotton), imbricate (margins overlap but not in any particular direction – Cassia, gulmohur) and vexillary or papilionaceous (pea and bean: the largest petal, the standard, overlaps the two lateral petals, the wings, which in turn overlap the two smallest anterior petals, the keel).
(b) Placentation. The arrangement of ovules within the ovary (the ovules are attached to a cushion-like placenta). Types: marginal (pea), axile (China rose, tomato, lemon), parietal (mustard, Argemone), basal (sunflower, marigold), central and free central (Dianthus, primrose) — described fully in Question 7.
(c) Actinomorphic flower. A flower with radial symmetry — it can be divided into two equal radial halves in any radial plane passing through the centre. Examples: mustard, datura, chilli.
(d) Zygomorphic flower. A flower with bilateral symmetry — it can be divided into two similar halves only in one particular vertical plane. Examples: pea, gulmohur, bean, Cassia. (A flower that cannot be divided into two similar halves by any vertical plane through the centre is asymmetric / irregular, as in canna.)
(e) Superior ovary. An ovary that is situated above the other floral parts (calyx, corolla, androecium) on the thalamus; it is seen in hypogynous flowers, where the gynoecium occupies the highest position and the other parts lie below it. Examples: mustard, China rose, brinjal.
(f) Perigynous flower. A flower in which the gynoecium is situated in the centre and the other parts of the flower are located on the rim of the thalamus almost at the same level; the ovary is said to be half inferior. Examples: plum, rose, peach.
(g) Epipetalous stamen. A stamen that is attached (adnate) to the petals. Example: brinjal (and all Solanaceae, with five stamens attached to the corolla). (When stamens are attached to the perianth, as in lily, they are called epiphyllous.)
| Term | Definition (key words) | Example |
|---|---|---|
| Aestivation | Arrangement of sepals / petals in the bud | Calotropis (valvate), China rose (twisted) |
| Placentation | Arrangement of ovules within the ovary | Pea (marginal), tomato (axile), mustard (parietal) |
| Actinomorphic | Radial symmetry; divisible in any radial plane | Mustard, datura, chilli |
| Zygomorphic | Bilateral symmetry; divisible in one vertical plane only | Pea, gulmohur, bean, Cassia |
| Superior ovary | Ovary above the other floral parts (hypogynous flower) | Mustard, China rose, brinjal |
| Perigynous flower | Gynoecium in centre, other parts on thalamus rim; ovary half inferior | Plum, rose, peach |
| Epipetalous stamen | Stamens attached to petals | Brinjal |
Conclusion: aestivation is the arrangement of floral members in the bud; placentation is the arrangement of ovules in the ovary; actinomorphic and zygomorphic flowers show radial and bilateral symmetry; a superior ovary lies above the other parts (hypogynous); a perigynous flower has its parts on the thalamus rim with a half-inferior ovary; and epipetalous stamens are attached to the petals.
Differentiate between (a) Racemose and cymose inflorescence (b) Apocarpous and syncarpous ovary
Concept. Inflorescence is the arrangement of flowers on the floral axis. Depending on whether the apex of the axis develops into a flower or continues to grow, two major types are defined — racemose and cymose. A gynoecium is made of one or more carpels; when there is more than one they may be free or fused — apocarpous or syncarpous.
(a) Racemose and cymose inflorescence
| Basis | Racemose inflorescence | Cymose inflorescence |
|---|---|---|
| Main axis | Continues to grow (unlimited growth) | Terminates in a flower (limited growth) |
| Position of flowers | Borne laterally on the axis | Terminal flower, with lateral flowers on branches below |
| Order of opening | Acropetal succession — older flowers at the base, younger towards the apex | Basipetal order — oldest flower at the top (terminal), younger ones towards the base |
| Apex | Apical meristem remains active | Apex is used up in forming the terminal flower |
| Growth of axis | Indefinite | Definite |
(b) Apocarpous and syncarpous ovary
| Basis | Apocarpous | Syncarpous |
|---|---|---|
| Carpels | Free — carpels are not united | Fused — carpels are united with each other |
| Number of carpels | Two or more, each with its own ovary, style and stigma | Two or more, fused into a compound ovary (style and stigma may be fused or free) |
| Ovary | Each carpel forms a separate ovary — many ovaries in a flower | A single compound ovary (uni- or multilocular) |
| Fruit formed | Many small fruitlets (aggregate of fruits) from one flower | A single fruit from one flower |
| Examples (NCERT) | Lotus, rose | Mustard, tomato |
Extra depth. A flower with a single carpel is monocarpellary; the drupes of mango and coconut develop from monocarpellary superior ovaries. Syncarpous ovaries are the common condition in advanced families such as Solanaceae (bicarpellary, syncarpous) and mustard.
Conclusion: in a racemose inflorescence the axis continues to grow with flowers in acropetal order, while in a cymose inflorescence the axis ends in a flower with flowers in basipetal order; an apocarpous gynoecium has free carpels (lotus, rose) whereas a syncarpous gynoecium has fused carpels (mustard, tomato).
Draw the labelled diagram of the following: (i) gram seed (ii) V.S. of maize seed
Concept. A seed is the fertilised, matured ovule; it consists of a seed coat and an embryo. The embryo has a radicle, an embryonal axis and one (monocot) or two (dicot) cotyledons. Gram is a dicotyledonous, non-endospermous seed; maize is a monocotyledonous, endospermic seed (a cereal grain, in which the seed coat is fused with the fruit wall).
(i) Gram seed (dicotyledonous seed) — Fig. 5.14
- Seed coat — the outermost covering, of two layers: outer testa and inner tegmen.
- Hilum — a scar on the seed coat through which the developing seed was attached to the fruit.
- Micropyle — a small pore above the hilum (for entry of water at germination).
- Embryo — inside the seed coat, consisting of an embryonal axis and two cotyledons. The cotyledons are often fleshy and full of reserve food materials.
- Radicle and plumule — at the two ends of the embryonal axis: the radicle is the future root and the plumule is the future shoot.
- Endosperm — absent in the mature seed of gram, pea and bean (non-endospermous seeds); castor has an endospermic dicot seed.
(ii) V.S. of a maize seed (monocotyledonous seed) — Fig. 5.15
- Seed coat and fruit wall — the seed coat is membranous and generally fused with the fruit wall.
- Endosperm — bulky and stores food (starch); its outer covering separates it from the embryo by a proteinous layer, the aleurone layer.
- Embryo — small, situated in a groove at one end of the endosperm. It consists of one large, shield-shaped cotyledon called the scutellum and a short axis with a plumule and a radicle.
- Coleoptile and coleorhiza — the plumule and radicle are enclosed in protective sheaths: the coleoptile covers the plumule and the coleorhiza covers the radicle.
| Feature | Gram seed (dicot) | Maize grain (monocot) |
|---|---|---|
| Number of cotyledons | Two (fleshy) | One — scutellum (shield-shaped) |
| Endosperm | Absent in mature seed (non-endospermous) | Present, bulky (endospermic) |
| Seed coat | Testa + tegmen; separate from the fruit wall | Membranous, fused with the fruit wall |
| Aleurone layer | Absent | Present |
| Sheaths round embryonal axis | Absent | Coleoptile (plumule) and coleorhiza (radicle) |
| Hilum and micropyle | Visible | Not prominent in the grain |
Conclusion: the gram seed shows seed coat, hilum, micropyle, two fleshy cotyledons, plumule and radicle with no endosperm, while the V.S. of a maize grain shows the fused seed coat and fruit wall, aleurone layer, bulky endosperm and an embryo with scutellum, plumule enclosed in coleoptile and radicle enclosed in coleorhiza.
Take one flower of the family Solanaceae and write its semi-technical description. Also draw its floral diagram.
Concept. A semi-technical description describes a flowering plant briefly, in simple scientific language and in a proper sequence: habit → vegetative characters (root, stem, leaves) → floral characters (inflorescence, flower and its whorls) → fruit and seed → floral formula and floral diagram. Solanaceae is a large family commonly called the ‘potato family’, widely distributed in the tropics, subtropics and temperate zones. The plant chosen is Solanum nigrum (makoi), as in Fig. 5.17 of NCERT.
Semi-technical description of Solanum nigrum (Family: Solanaceae)
| Part | Description |
|---|---|
| Habit | Herb (the family has mostly herbs, shrubs and rarely small trees) |
| Root | Tap root system with lateral roots (dicotyledonous plant) |
| Stem | Herbaceous, aerial, erect, cylindrical, branched, solid or hollow, hairy or glabrous (underground tuber in potato, Solanum tuberosum) |
| Leaves | Alternate, simple, petiolate, exstipulate (without stipules); venation reticulate |
| Inflorescence | Solitary, axillary or cymose as in Solanum |
| Flower | Bisexual, actinomorphic, pentamerous, hypogynous |
| Calyx | Sepals five, united (gamosepalous), persistent, valvate aestivation |
| Corolla | Petals five, united (gamopetalous), valvate aestivation |
| Androecium | Stamens five, epipetalous (attached to the corolla) |
| Gynoecium | Bicarpellary, obliquely placed, syncarpous; ovary superior, bilocular; placenta swollen with many ovules; axile placentation |
| Fruit | Berry or capsule |
| Seeds | Many, endospermous |
| Floral formula | ⊕ ⚥ K(5) C(5) A5 G(2) |
How to read the floral formula. ⊕ = actinomorphic; ⚥ = bisexual; K(5) = calyx of 5 sepals, brackets show fusion (united); C(5) = corolla of 5 united petals; A5 = 5 free-looking stamens that are adnate to the petals (a line above the symbols A and C shows adhesion, i.e., epipetalous); G(2) = gynoecium of 2 fused (syncarpous) carpels, the underline indicating a superior ovary.
Explanation of the floral diagram. The dot at the top represents the mother axis; the calyx is the outermost whorl, followed by the corolla, then the androecium, with the gynoecium in the centre. Sepals and petals are drawn touching each other at their margins (valvate) and joined (united); the five stamens are shown alternating with the petals and connected to them by lines (epipetalous); the central bilocular ovary shows axile placentation with a swollen placenta bearing many ovules.
Economic importance (NCERT). Food – tomato, brinjal, potato; spice – chilli; medicine – belladonna, ashwagandha; fumigatory – tobacco; ornamental – petunia.
Conclusion: a Solanaceae flower (Solanum) is bisexual and actinomorphic with five united valvate sepals, five united valvate petals, five epipetalous stamens and a bicarpellary, syncarpous, superior, bilocular ovary with axile placentation, represented by the formula ⊕ ⚥ K(5) C(5) A5 G(2).
Describe the various types of placentations found in flowering plants.
Concept. Each ovary bears one or more ovules, attached to a flattened, cushion-like placenta. The arrangement of ovules within the ovary is called placentation. Different families have different, constant types, which makes placentation a useful taxonomic character. NCERT describes the types as marginal, axile, parietal, basal, central and free central (Fig. 5.12).
- Marginal placentation. The placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge, forming two rows. The ovary is unilocular (one-chambered), made of a single carpel. Example: pea (and other legumes).
- Axile placentation. The placenta is axial (in the centre, formed by the fusion of the carpel margins) and the ovules are attached to it in a multilocular ovary — each chamber (locule) has ovules attached to the central axis. Examples: China rose, tomato, lemon (also Solanaceae).
- Parietal placentation. The ovules develop on the inner wall of the ovary or on its peripheral part. The ovary is one-chambered but becomes two-chambered due to the formation of a false septum. Examples: mustard and Argemone.
- Free central placentation. The ovules are borne on a central axis and septa are absent (the ovary is unilocular). Examples: Dianthus and primrose.
- Basal placentation. The placenta develops at the base of the ovary and a single ovule is attached to it. Examples: sunflower and marigold.
| Type | Position of ovules | Ovary chambers | Examples (NCERT) |
|---|---|---|---|
| Marginal | On a ridge along the ventral suture, in two rows | One (monocarpellary) | Pea |
| Axile | On the central axis, in each locule | Many (multilocular) | China rose, tomato, lemon |
| Parietal | On the inner wall / periphery of the ovary | One, made two by a false septum | Mustard, Argemone |
| Free central | On a central axis, no septa | One | Dianthus, primrose |
| Basal | At the base of the ovary; a single ovule | One | Sunflower, marigold |
Extra depth. After fertilisation, the ovules develop into seeds and the ovary matures into a fruit, so the placentation type also decides how seeds are arranged inside the fruit (e.g., seeds in rows in the pea pod; seeds in each chamber of a tomato).
Conclusion: placentation, the arrangement of ovules in the ovary, is of the marginal (pea), axile (China rose, tomato, lemon), parietal (mustard, Argemone), free central (Dianthus, primrose) and basal (sunflower, marigold) types.
What is a flower? Describe the parts of a typical angiosperm flower.
Concept — what is a flower? A flower is a modified shoot in which the shoot apical meristem changes into a floral meristem; the internodes do not elongate, the axis becomes condensed, and the apex produces different kinds of floral appendages laterally at successive nodes instead of leaves. A flower is the reproductive unit of the angiosperms, meant for sexual reproduction.
Parts of a typical flower. The flower is borne on a stalk, the pedicel, whose swollen end is the thalamus (receptacle). On the thalamus four kinds of whorls are arranged successively: calyx, corolla, androecium and gynoecium (Fig. 5.10). Calyx and corolla are accessory organs; androecium and gynoecium are the reproductive organs. In some flowers, such as lily, the calyx and corolla are not distinct and are called the perianth.
- Calyx. The outermost whorl; its members are the sepals, generally green and leaf-like, which protect the flower in the bud stage. The calyx may be gamosepalous (sepals united) or polysepalous (sepals free).
- Corolla. Composed of petals, usually brightly coloured to attract insects for pollination. It may be gamopetalous (petals united) or polypetalous (free); the shape and colour vary greatly — tubular, bell-shaped, funnel-shaped or wheel-shaped. Aestivation is the arrangement of sepals or petals in the bud (valvate, twisted, imbricate, vexillary).
- Androecium. Composed of stamens, the male reproductive organs. Each stamen consists of a filament (stalk) and an anther; each anther is usually bilobed and each lobe has two chambers, the pollen-sacs, in which pollen grains are produced. A sterile stamen is a staminode. Stamens may be free (polyandrous) or united — monoadelphous (China rose), diadelphous (pea), polyadelphous (citrus); they may be attached to petals (epipetalous, brinjal) or to the perianth (epiphyllous, lily).
- Gynoecium. The female reproductive part, made up of one or more carpels. A carpel has three parts: stigma (receptive surface for pollen, at the tip), style (elongated tube connecting ovary to stigma) and ovary (enlarged basal part) bearing one or more ovules attached to the placenta. Carpels may be free (apocarpous, lotus, rose) or fused (syncarpous, mustard, tomato). After fertilisation the ovules become seeds and the ovary becomes a fruit.
Types of flowers. Bisexual — both androecium and gynoecium present; unisexual — only stamens or only carpels. By symmetry — actinomorphic (radial), zygomorphic (bilateral) or asymmetric. By the number of parts — trimerous, tetramerous, pentamerous (multiples of 3, 4, 5). With or without bracts (reduced leaves at the base of the pedicel) — bracteate or ebracteate.
| Whorl | Members | Function | Nature |
|---|---|---|---|
| Calyx | Sepals | Protect the bud; photosynthesis (green) | Accessory (non-essential) organ |
| Corolla | Petals | Attract insects for pollination | Accessory organ |
| Androecium | Stamens (filament + anther) | Produce pollen grains (male) | Reproductive organ |
| Gynoecium | Carpels (stigma + style + ovary) | Receive pollen; ovules → seeds, ovary → fruit (female) | Reproductive organ |
Conclusion: a flower is a modified shoot meant for sexual reproduction; a typical flower, borne on a pedicel and thalamus, has four whorls — calyx (sepals), corolla (petals), androecium (stamens) and gynoecium (carpels with stigma, style and ovary) — of which androecium and gynoecium are the reproductive organs.
Define the term inflorescence. Explain the basis for the different types inflorescence in flowering plants.
Concept — definition. The arrangement of flowers on the floral axis is called inflorescence. A flower itself is a modified shoot: when a shoot tip transforms into a flower it is always solitary; when the shoot continues to grow and bears flowers on its sides, an inflorescence results.
Basis of the types of inflorescence. The types depend on whether the apex of the floral axis develops into a flower or continues to grow. On this basis two major types are defined — racemose and cymose (Figs 5.7 and 5.8, shown in Question 4):
- Racemose inflorescence — the main axis continues to grow (the apex does not end in a flower); the flowers are borne laterally in an acropetal succession, i.e., the older flowers are at the base and the younger flowers towards the tip.
- Cymose inflorescence — the main axis terminates in a flower, hence its growth is limited; the flowers are borne in a basipetal order, i.e., the oldest flower is at the apex and the younger flowers are towards the base.
| Criterion (basis) | Racemose | Cymose |
|---|---|---|
| Fate of the apex of the axis | Continues to grow (does not become a flower) | Develops into a flower (growth stops) |
| Growth of the axis | Unlimited | Limited |
| Order of development of flowers | Acropetal (base → apex) | Basipetal (apex → base) |
| Position of oldest flower | At the base | At the apex (terminal) |
Extra depth. Acropetal means “towards the apex” (new flowers form near the tip) and basipetal means “towards the base”. The same words are used for the arrangement of leaves (acropetal order at the stem apex, Section 5.3). A solitary flower, as in Solanaceae, is the simplest case when the shoot tip itself becomes a flower.
Conclusion: inflorescence is the arrangement of flowers on the floral axis, and its types depend on whether the apex of the axis keeps growing (racemose, flowers in acropetal succession) or ends in a flower (cymose, flowers in basipetal order).
Describe the arrangement of floral members in relation to their insertion on thalamus.
Concept. On the thalamus (receptacle) the calyx, corolla and androecium are inserted at a position relative to the ovary (gynoecium). Based on this position, flowers are described as hypogynous, perigynous and epigynous (Fig. 5.9).
- Hypogynous flower. The gynoecium occupies the highest position on the thalamus while the other parts (calyx, corolla, androecium) are situated below it. The ovary is said to be superior. Examples: mustard, China rose and brinjal.
- Perigynous flower. The gynoecium is situated in the centre and the other parts of the flower are located on the rim of the thalamus almost at the same level. The ovary is said to be half inferior. Examples: plum, rose and peach.
- Epigynous flower. The margin of the thalamus grows upward, enclosing the ovary completely and getting fused with it; the other parts of the flower arise above the ovary. Hence the ovary is said to be inferior. Examples: guava and cucumber, and the ray florets of sunflower.
| Type | Position of gynoecium | Position of other floral parts | Ovary | Examples (NCERT) |
|---|---|---|---|---|
| Hypogynous | Highest position | Below the ovary | Superior | Mustard, China rose, brinjal |
| Perigynous | In the centre | On the rim of the thalamus, at about the same level | Half inferior | Plum, rose, peach |
| Epigynous | Enclosed by, and fused with, the thalamus | Arise above the ovary | Inferior | Guava, cucumber, ray florets of sunflower |
Extra depth. The position of the ovary also decides the kind of fruit: superior ovaries form true fruits, while inferior ovaries (guava, cucumber) produce fruits in which the thalamus also contributes (standard knowledge). The position is a key character in the descriptions of plant families (Solanaceae is hypogynous).
Conclusion: in hypogynous flowers the gynoecium is highest and the ovary is superior (mustard), in perigynous flowers the gynoecium is central with other parts on the thalamus rim and a half-inferior ovary (rose), and in epigynous flowers the thalamus encloses and fuses with the ovary, which is inferior (guava).