Spermatophyte: Gymnosperms and Angiosperm Morphology BBO2T03

Syllabus topics (official RTMNU)

1. Gymnosperms: General characteristics, Classification (Stewart, 1982) and Economic Importance
2. Fossil Gymnosperms: Cycadeoidea (Morphology and Reproductive structure)
3. Life cycle of: Cycas (Morphology, Anatomy and Reproductive structures)

Gymnosperms: General characteristics, Classification (Stewart, 1982) and Economic Importance

Definition: Gymnosperms are seed plants whose ovules are not enclosed in an ovary; they lie exposed on megasporophylls or cone scales. Hence the seeds are "naked". They were dominant in the Mesozoic era.

General characteristics

• Mostly woody, perennial, evergreen trees or shrubs (tallest: Sequoia).
• Plant body is the diploid sporophyte, differentiated into root, stem and leaves. Tap root system; coralloid roots in Cycas (with cyanobacteria) and mycorrhizal roots in Pinus.
• Vascular bundles are conjoint, collateral, open; secondary growth present. Xylem has tracheids but no vessels (except Gnetales); phloem has sieve cells but no companion cells (albuminous cells instead).
• Plants are heterosporous: microspores (pollen) and megaspores. Sporophylls usually grouped into male and female cones (strobili). Plants monoecious (Pinus) or dioecious (Cycas).
• No flowers, no ovary, no style and stigma; hence no fruit is formed.
• Wind pollination; pollen lands directly on the ovule, caught by a pollination drop.
• Male gametophyte is highly reduced; female gametophyte (endosperm) is haploid and formed before fertilisation. Archegonia are present (except Gnetum, Welwitschia).
• Fertilisation by siphonogamy (pollen tube). Male gametes are motile and ciliated in Cycas and Ginkgo; non-motile in conifers.
• Polyembryony is common. No double fertilisation (true double fertilisation absent).

Classification (Stewart, 1982) – W.N. Stewart in "Paleobotany and the Evolution of Plants" placed gymnosperms (living and fossil) in Division Gymnospermophyta with three classes:

Within class Gymnospermopsida two lines are recognised: the cycad line (seed ferns, Bennettitales, Cycadales) with manoxylic wood (soft, much parenchyma), large pinnate leaves and radiospermic seeds, and the conifer line (Cordaitales, Ginkgoales, Coniferales, Taxales) with pycnoxylic wood (compact), small simple leaves and platyspermic seeds.

Economic importance

• Timber: Cedrus deodara, Pinus, Abies – furniture, construction, plywood.
• Paper pulp: Pinus, Picea.
• Resin, turpentine from Pinus roxburghii; Canada balsam (mountant) from Abies balsamea.
• Food: sago starch from Cycas pith; chilgoza seeds of Pinus gerardiana.
• Medicine: Ephedrine from Ephedra (asthma, cold); Taxol (anticancer) from Taxus; Ginkgo biloba extract for memory and blood circulation.
• Ornamental: Cycas, Thuja, Araucaria.

Fossil Gymnosperms: Cycadeoidea (Morphology and Reproductive structure)

Systematic position: Class Gymnospermopsida (Cycadopsida), Order Cycadeoidales (Bennettitales), Family Cycadeoidaceae. Genus Cycadeoidea lived from the Triassic to the Cretaceous (Mesozoic). Petrified fossils from the USA were studied in detail by G.R. Wieland.

Morphology

• Stem short, stout, barrel-shaped or globose, up to about 1 m tall.
• The stem surface is covered by an armour of persistent leaf bases with dense ramentum (hairs).
• A crown of large pinnately compound leaves (cycad-like) at the apex.
• Internally: large pith, a ring of bundles with manoxylic wood, large cortex; leaf traces simple (not girdling).
• Stomata are syndetocheilic (subsidiary cells from the same mother cell as guard cells) – a key difference from cycads (haplocheilic).

Reproductive structure ("flower")

• Cones were borne laterally among the leaf bases, sunk in the armour.
• Cones were bisporangiate (bisexual), resembling an angiosperm flower – hence called "flowers".
• From base to apex the cone shows: (1) a short peduncle bearing spirally arranged hairy bracts (perianth-like); (2) a whorl of about 10–20 microsporophylls, pinnate, fused at the base into a cup (like a fern frond), bearing synangia (fused microsporangia) on pinnae; they were incurved in bud; (3) a central conical or dome-shaped receptacle (ovulate region).
• The receptacle bore numerous long-stalked orthotropous ovules intermixed with interseminal scales. The expanded tips of interseminal scales formed a protective layer with openings only for micropyles.
• Each ovule had a single integument extended into a long micropylar tube. Seeds were small, dicotyledonous and exalbuminous (embryo almost fills the seed).

Significance: The bisexual, flower-like cone of Cycadeoidea led to the Bennettitalean (Anthostrobilus) theory of angiosperm origin (Arber and Parkin, 1907).

Life cycle of: Cycas (Morphology, Anatomy and Reproductive structures)

Systematic position: Gymnospermopsida – Cycadales – Cycadaceae. Example: Cycas revoluta. Called a "living fossil".

Morphology (sporophyte)

• Palm-like, 1–3 m tall; stem unbranched, columnar, covered by persistent bases of foliage and scale leaves.
• Roots: tap root; coralloid roots – apogeotropic, dichotomously branched, swollen, containing the cyanobacteria Anabaena/Nostoc in the cortex (nitrogen fixation).
• Leaves dimorphic: (a) foliage leaves – large, pinnately compound, crowded at the stem apex; young leaflets show circinate vernation; each leaflet has a single midrib and no lateral veins; (b) scale leaves – brown, dry, hairy, protective.

Anatomy

• Coralloid root: cortex with a distinct algal zone between outer and inner cortex.
• Stem T.S.: outline irregular due to leaf bases; large parenchymatous cortex with mucilage canals and girdle leaf traces; a ring of conjoint, collateral, open, endarch bundles; large pith; manoxylic wood; secondary growth by successive cambia (polyxylic in old stems).
• Rachis T.S.: omega (Ω)-shaped arrangement of vascular bundles; each bundle diploxylic (centripetal xylem exarch + centrifugal xylem endarch).
• Leaflet T.S.: xerophytic – thick cuticle, sclerenchymatous hypodermis, palisade only on upper side, sunken stomata on lower side, transfusion tissue (primary beside the midrib and secondary/accessory transfusion tissue running across the mesophyll to the margins). Midrib bundle is diploxylic.

Reproductive structures – Cycas is dioecious.

• Male cone: large, compact, terminal. Numerous spirally arranged, woody, wedge-shaped microsporophylls, each with a sterile upturned apex (apophysis). Lower (abaxial) surface bears thousands of microsporangia in sori (groups of 2–6). Microspore mother cells undergo meiosis forming microspores (pollen).
• Female "cone": no true cone; megasporophylls are produced in a loose rosette at the apex, and the stem apex keeps growing through them. Each megasporophyll is leaf-like with a petiole bearing 2–10 ovules on its margins.
• Ovule: the largest ovules in the plant kingdom (up to 6 cm in C. thouarsii); orthotropous, one thick integument with three layers (outer fleshy, middle stony, inner fleshy), nucellus with a beak, pollen chamber, female gametophyte (endosperm) bearing 2–8 archegonia at the micropylar end, and an archegonial chamber.

Gametophytes and fertilisation

• Microspore forms 3-celled pollen (prothallial, generative, tube cell). Wind pollination; pollination drop draws pollen into the pollen chamber.
• Generative cell divides into stalk cell and body cell; body cell forms two large top-shaped, multiciliated antherozoids (the largest male gametes, about 300 µm, visible to the naked eye).
• Pollen tube is haustorial (absorbs food from nucellus). It bursts and releases gametes into the archegonial chamber; one antherozoid fuses with the egg → zygote (zooidogamy with siphonogamy).
• Embryo develops with a suspensor; seed has two cotyledons, haploid endosperm and stony seed coat. Polyembryony occurs.

5 likely exam questions

Long answer

1. Give an account of general characteristics and economic importance of gymnosperms. Add a note on classification of gymnosperms proposed by Stewart (1982).
2. Describe the morphology, anatomy of the leaflet and reproductive structures of Cycas with labelled diagrams.

Short answer / short notes

3. Describe the reproductive structure (bisexual cone) of Cycadeoidea.
4. Write a note on coralloid roots of Cycas.
5. Draw a labelled diagram of L.S. of the ovule of Cycas.

Syllabus topics (official RTMNU)

1. Root: Tap root and adventitious root, modification of root for storage and respiration.
2. Stem: Branching (Monopodial and Sympodial), Modification of stem (Runner, Suckers, Rhizome, Tuber, Bulb)
3. Leaf: Typical leaf, Types (Simple and Compound), Types of phyllotaxy, Venation, Modification of leaf (Tendril, Phyllode)

Root: Tap root and adventitious root, modification of root for storage and respiration.

Root: the descending, non-green, positively geotropic part of the plant axis, without nodes, internodes, leaves or buds. Functions: anchorage, absorption of water and minerals, conduction, storage. Regions: root cap, region of cell division, elongation, root-hair zone and maturation.

A. Tap root modified for storage (the swollen primary root; named by shape):

• Fusiform – swollen in the middle, tapering at both ends: radish (Raphanus sativus).
• Napiform – very swollen at top (spherical), abruptly tapering below: turnip (Brassica rapa), beetroot (Beta vulgaris).
• Conical – broad at base, gradually tapering to apex: carrot (Daucus carota).

B. Adventitious root modified for storage:

• Tuberous – single swollen roots without definite shape: sweet potato (Ipomoea batatas).
• Fasciculated – a cluster of swollen roots from the stem base: Dahlia, Asparagus.
• Nodulose – roots swollen only near the tips: mango ginger (Curcuma amada), Maranta.
• Moniliform (beaded) – alternate swellings and constrictions like a bead necklace: Momordica, Vitis, some grasses.
• Annulated – ring-like swellings: ipecac (Psychotria ipecacuanha).

C. Root modified for respiration – Pneumatophores (breathing roots)

• Found in mangroves (halophytes) growing in saline, marshy, waterlogged soil where oxygen is scarce, e.g. Rhizophora, Avicennia, Sonneratia, Heritiera.
• Branches of underground roots grow vertically upward (negatively geotropic) and come out of the mud as conical, peg-like projections.
• Their surface bears many small pores called lenticels/pneumathodes through which air enters; internal aerenchyma carries oxygen to submerged roots.

Stem: Branching (Monopodial and Sympodial), Modification of stem (Runner, Suckers, Rhizome, Tuber, Bulb)

Stem: the ascending axis developing from the plumule; bears nodes, internodes, leaves, buds and flowers. Positively phototropic.

Branching – lateral (axillary) branching is of two types:

Modifications of stem – all modified stems are identified by the presence of nodes, internodes, scale leaves and axillary buds.

(a) Sub-aerial modifications (for vegetative propagation):

• Runner – slender, creeping stem with long internodes running horizontally on the soil; roots arise from the lower side and leaves from the upper side of each node; new plants form at nodes. E.g. Cynodon dactylon (doob grass), Oxalis, Centella.
• Sucker – a lateral branch arising from the underground base of the stem, grows horizontally under the soil for some distance and then comes up obliquely to form a new leafy shoot. E.g. Chrysanthemum, mint (Mentha), banana, pineapple.

(b) Underground modifications (for food storage and perennation):

• Rhizome – a thick, fleshy, horizontally growing underground stem with distinct nodes and internodes, scale leaves, axillary and terminal buds and adventitious roots. E.g. ginger (Zingiber officinale), turmeric (Curcuma longa), Canna.
• Stem tuber – swollen tip of an underground branch (stolon), storing starch. Surface shows depressions called "eyes", each with an axillary bud and a scale leaf (= node). E.g. potato (Solanum tuberosum).
• Bulb – a highly reduced, disc-like convex stem at the base, bearing many fleshy scale leaves that store food, with adventitious roots below. Tunicated bulb – scale leaves concentric, covered by dry outer scales (onion, Allium cepa); scaly (imbricate) bulb – scales overlap loosely (garlic, Allium sativum; Lilium).

Leaf: Typical leaf, Types (Simple and Compound), Types of phyllotaxy, Venation, Modification of leaf (Tendril, Phyllode)

Leaf: a green, flat, lateral outgrowth of the stem borne at a node, with a bud in its axil; main organ of photosynthesis and transpiration.

Typical leaf – parts:

• Leaf base (hypopodium) – attaches the leaf to the node; may bear two lateral outgrowths, the stipules; swollen leaf base = pulvinus (legumes); sheathing base in grasses.
• Petiole (mesopodium) – stalk; leaf with petiole = petiolate, without = sessile.
• Lamina (epipodium) – flat green blade with a midrib, veins and veinlets.

Types of leaves

• Simple leaf – lamina entire or incised, but incisions do not reach the midrib (mango, Hibiscus).
• Compound leaf – incisions reach the midrib/petiole, dividing the lamina into separate leaflets. Leaflets have no axillary buds (the whole leaf has one).
  Pinnately compound – leaflets on a common axis (rachis): unipinnate (rose, neem; paripinnate – even number, imparipinnate – odd number), bipinnate (Acacia, Mimosa), tripinnate (Moringa), decompound (coriander).
  Palmately compound – leaflets attached at the tip of the petiole: unifoliate (Citrus), bifoliate (Balanites), trifoliate (Aegle), quadrifoliate (Marsilea), multifoliate (Bombax).

Phyllotaxy – arrangement of leaves on the stem:

• Alternate (spiral) – one leaf per node: Hibiscus, mustard, sunflower.
• Opposite – two leaves per node opposite each other: superposed (all pairs in one plane – guava, Quisqualis) or decussate (successive pairs at right angles – Calotropis, Ocimum).
• Whorled (verticillate) – more than two leaves per node: Nerium, Alstonia.

Venation – arrangement of veins in the lamina:

Modifications of leaf

• Leaf tendril – the whole leaf or a part becomes a thin, coiled, sensitive structure for climbing. Whole leaf: Lathyrus aphaca (wild pea; stipules become leaf-like); terminal leaflets: garden pea (Pisum sativum); leaf apex: Gloriosa; stipules: Smilax.
• Phyllode – the petiole becomes flat, green and leaf-like and performs photosynthesis, while the true lamina is lost early (reduction of transpiration in xerophytes). E.g. Australian Acacia (A. auriculiformis, A. melanoxylon), Parkinsonia. Phyllodes are often placed vertically.

5 likely exam questions

Long answer

1. What is a root? Describe the modifications of tap root and adventitious root for storage, and the roots modified for respiration, with suitable examples and diagrams.
2. Describe the underground and sub-aerial modifications of stem with suitable examples. Add a note on monopodial and sympodial branching.

Short answer / short notes

3. Differentiate between simple and compound leaves with examples.
4. What is a phyllode? Give an example.
5. Explain the different types of phyllotaxy with examples.

Syllabus topics (official RTMNU)

1. Inflorescence: Definition, Racemose, Cymose and Special types.
2. Flower: Structure of Typical flower, insertion of floral whorls, Variation in thalamus (Androphore, Gynophore and Gynandrophore)
3. Calyx and Corolla: Cohesion, Forms of corolla and Aestivation.
4. Androecium: Parts, Cohesion, Adhesion and Fixation.

Inflorescence: Definition, Racemose, Cymose and Special types.

Definition: The arrangement of flowers on the floral axis is called inflorescence. The main axis is the peduncle; the stalk of each flower is the pedicel. A peduncle arising from an underground stem is a scape (onion).

A. Racemose (indefinite) – main axis grows indefinitely; flowers arise in acropetal succession (older below, younger above); opening is centripetal.

• Raceme – elongated axis, pedicellate flowers: mustard, radish. Compound raceme (panicle): Delonix, Mangifera.
• Spike – elongated axis, sessile flowers: Achyranthes, Adhatoda. Spikelet: grasses, wheat.
• Catkin – pendulous spike of unisexual flowers: mulberry (Morus), Acalypha.
• Spadix – fleshy spike enclosed by a large bract (spathe): Colocasia, banana, palms.
• Corymb – lower pedicels longer so all flowers come to one level: candytuft (Iberis), Cassia.
• Umbel – axis reduced; flowers arise from one point, with a whorl of bracts (involucre): Allium; compound umbel – coriander, carrot.
• Capitulum (head) – axis flattened into a receptacle bearing sessile florets, surrounded by involucre; ray florets outside, disc florets in centre: sunflower, Tridax.

B. Cymose (definite) – main axis ends in a flower; further growth by lateral branches; flowers in basipetal succession; opening centrifugal.

• Monochasial (uniparous) – one lateral branch each time: helicoid (branches on one side, coiled – Heliotropium, Drosera) or scorpioid (alternately on both sides – Ranunculus, Gossypium).
• Dichasial (biparous) – two lateral branches: Jasminum, Bougainvillea, Clerodendrum.
• Polychasial (multiparous) – more than two branches: Calotropis, Nerium.

C. Special types

• Cyathium – cup-like involucre of bracts with nectar gland; a central stalked female flower surrounded by many male flowers (each a single stamen) in scorpioid cymes: Euphorbia, Poinsettia.
• Verticillaster – a pair of dichasial cymes (later monochasial) at each node giving a false whorl: Ocimum, Leonotis (Lamiaceae).
• Hypanthodium – receptacle forms a hollow pear-shaped cup with an apical opening (ostiole); male flowers near the ostiole, female flowers at the base, gall flowers in between: Ficus.

Flower: Structure of Typical flower, insertion of floral whorls, Variation in thalamus (Androphore, Gynophore and Gynandrophore)

Flower: a highly condensed, modified shoot meant for sexual reproduction. A typical flower has a pedicel, a swollen tip called thalamus (receptacle), and four whorls: calyx (sepals, protective), corolla (petals, attractive), androecium (stamens, male) and gynoecium (carpels, female). Calyx and corolla are accessory whorls; androecium and gynoecium are essential whorls. When calyx and corolla are similar they are called perianth (tepals).

Insertion of floral whorls (position of whorls with respect to the ovary):

Variation in thalamus – internodes of the thalamus may elongate:

• Anthophore – internode between calyx and corolla (Silene) – for comparison.
• Androphore – internode between corolla and androecium elongates, raising the stamens: Passiflora (as given in most Indian textbooks).
• Gynophore – internode between androecium and gynoecium elongates, raising the ovary: Capparis, groundnut (after fertilisation gynophore pushes the ovary into soil).
• Gynandrophore (androgynophore) – internode below both androecium and gynoecium elongates, carrying both: Gynandropsis (Cleome gynandra).

Calyx and Corolla: Cohesion, Forms of corolla and Aestivation.

Cohesion = union of members of the same whorl. Free sepals = polysepalous; fused = gamosepalous. Free petals = polypetalous; fused = gamopetalous. Calyx persistent after fertilisation (brinjal, tomato), modified into pappus (Asteraceae) or petaloid (Mussaenda).

Forms of corolla

• Polypetalous, regular: Cruciform – 4 clawed petals in a cross (mustard); Caryophyllaceous – 5 petals with long claws at right angles to limb (Dianthus); Rosaceous – 5 petals without claws, spreading (rose).
• Polypetalous, irregular: Papilionaceous – one large posterior standard (vexillum), two lateral wings (alae), two anterior fused keel (carina) petals (pea, bean).
• Gamopetalous, regular: Tubular (disc floret of sunflower), Campanulate/bell-shaped (Physalis), Infundibuliform/funnel (Datura, Ipomoea), Rotate/wheel (brinjal), Hypocrateriform/salver (Vinca, Ixora).
• Gamopetalous, irregular: Bilabiate – two-lipped (Ocimum); Personate – two-lipped with throat closed by a palate (Antirrhinum); Ligulate – strap-shaped (ray floret of sunflower).

Aestivation – arrangement of sepals or petals in the bud:

• Valvate – margins just touch, no overlap: Calotropis, Annona.
• Twisted (contorted) – each petal overlaps the next on one side, regularly: Hibiscus, cotton.
• Imbricate – irregular overlapping; one petal fully inside, one fully outside: Cassia, gulmohur.
• Quincuncial – two petals outside, two inside, one half in half out: Ipomoea.
• Vexillary (descendingly imbricate) – standard overlaps wings, wings overlap keel: pea.

Androecium: Parts, Cohesion, Adhesion and Fixation.

Parts of a stamen: filament (stalk), anther (usually bilobed, each lobe with two pollen sacs – tetrasporangiate), and connective joining the two lobes. A sterile stamen is a staminode.

Cohesion of stamens

• Adelphous (filaments fused, anthers free): monadelphous – one bundle (Hibiscus, China rose); diadelphous – two bundles, (9)+1 (pea); polyadelphous – many bundles (Citrus, Bombax).
• Syngenesious – anthers fused, filaments free (sunflower, Asteraceae).
• Synandrous – stamens fused throughout (filaments and anthers): cucurbits.

Adhesion of stamens (union with other whorls): epipetalous – stamens attached to petals (brinjal, Datura); epiphyllous/epitepalous – attached to perianth (lily); gynandrous – stamens fused with gynoecium forming gynostegium (Calotropis) or gynostemium (orchids).

Length of stamens (often asked with this topic): didynamous – 2 long + 2 short (Ocimum); tetradynamous – 4 long + 2 short (mustard).

Fixation of anther (attachment to filament):

• Basifixed (innate) – filament attached at the base of the anther: mustard, Datura.
• Dorsifixed – attached on the back of the anther: Passiflora, Sesbania.
• Versatile – attached at a point in the middle so the anther swings freely (wind pollination): grasses, lily.
• Adnate – filament continues along the whole back of the anther: Michelia, Magnolia.

5 likely exam questions

Long answer

1. Define inflorescence. Describe racemose, cymose and special types of inflorescence with suitable examples and labelled diagrams.
2. Describe the structure of a typical flower. Explain the insertion of floral whorls and the variations in thalamus with examples.

Short answer / short notes

3. What is aestivation? Describe its types with examples.
4. Describe cohesion of stamens with examples.
5. Explain the different types of fixation of anther.

Syllabus topics (official RTMNU)

1. Gynoecium: Parts, Cohesion, Adhesion and Placentation.
2. Fruit: Definition, Pericarp, Types of fruits: Simple (Dehiscent, Schizocarpic, Dry Indehiscent, Fleshy Indehiscent); Aggregate (Etaerio) fruits, Composite Fruits (Sorosis and Syconus).

Gynoecium: Parts, Cohesion, Adhesion and Placentation.

Gynoecium (pistil) is the female, innermost whorl of the flower made of one or more carpels (megasporophylls).

Parts of a carpel/pistil:

• Ovary – basal swollen part containing ovules attached to a cushion-like tissue, the placenta. The ovary is divided into chambers (locules).
• Style – slender stalk arising from the ovary top; gynobasic style arises from the base of a deeply lobed ovary (Ocimum).
• Stigma – tip of the style which receives pollen; may be capitate, bifid, feathery (grasses), etc.

Cohesion of carpels

• Monocarpellary – one carpel: pea, bean, mango.
• Apocarpous – two or more carpels, free from each other: Ranunculus, lotus, Annona, Michelia.
• Syncarpous – two or more carpels fused: bicarpellary (mustard, Datura, tomato), tricarpellary (cucurbits, Euphorbia), tetracarpellary, pentacarpellary (Hibiscus, Citrus). Fusion may be of ovaries only, ovaries and styles, or complete.

Adhesion – union of the gynoecium with other whorls: fusion of ovary with thalamus forms an inferior ovary (epigynous flower – guava, cucumber); with free thalamus the ovary is superior; fusion with stamens is gynandry (Calotropis – gynostegium; orchids – gynostemium/column).

Placentation – the arrangement of placentae (and ovules) inside the ovary:

Fruit: Definition, Pericarp, Types of fruits: Simple (Dehiscent, Schizocarpic, Dry Indehiscent, Fleshy Indehiscent); Aggregate (Etaerio) fruits, Composite Fruits (Sorosis and Syconus).

Definition: A fruit is a mature or ripened ovary, developed after fertilisation, containing seeds. A fruit formed without fertilisation is parthenocarpic (seedless – banana, grape). If other floral parts (thalamus, calyx) take part, it is a false fruit (pseudocarp) – apple (thalamus), cashew (pedicel).

Pericarp: the fruit wall, developed from the ovary wall. In fleshy fruits it has three layers: epicarp (outer skin), mesocarp (middle, often fleshy) and endocarp (inner, may be stony or membranous).

Classification of fruits

I. Simple fruits – from a single ovary (mono- or syncarpous) of one flower.

(A) Dry dehiscent (pericarp splits to release seeds):

• Legume (pod) – monocarpellary, dehisces along both sutures: pea, bean.
• Follicle – monocarpellary, dehisces along one (ventral) suture: Calotropis, Michelia (they bear follicles in groups, so the whole fruit is an etaerio of follicles).
• Siliqua – bicarpellary, long, opens from base upwards; seeds on replum: mustard. A short broad siliqua is a silicula (Capsella).
• Capsule – multicarpellary, opens in various ways (pores, valves): cotton, Datura, poppy, lady's finger.

(B) Schizocarpic (dry fruit breaking into one-seeded parts, the mericarps):

• Lomentum – a legume constricted between seeds, breaking into one-seeded pieces: Mimosa, groundnut (indehiscent form), Acacia.
• Cremocarp – bicarpellary, splits into two mericarps hanging on a forked carpophore: coriander, fennel (Apiaceae).
• Carcerulus – splits into many one-seeded nutlets: Ocimum, Abutilon.
• Regma – tricarpellary, splits into cocci (three-seeded parts): castor (Ricinus), Geranium.

(C) Dry indehiscent (pericarp does not split; usually one-seeded):

• Caryopsis – pericarp fused with the seed coat: wheat, rice, maize.
• Achene – pericarp free from seed coat: Clematis, Mirabilis.
• Cypsela – from inferior bicarpellary ovary, with pappus: sunflower, Tridax.
• Nut – hard woody pericarp: cashew, litchi, oak.
• Samara – winged pericarp: Hiptage, Holoptelea.

(D) Fleshy indehiscent:

• Drupe (stone fruit) – stony endocarp: mango (fleshy mesocarp), coconut (fibrous mesocarp), plum.
• Berry – fleshy throughout, many seeds: tomato, guava, grape, brinjal.
• Pepo – inferior tricarpellary ovary, parietal placentation, hard rind: cucumber, watermelon.
• Hesperidium – leathery rind with oil glands, juicy hairs from endocarp: orange, lemon.
• Pome – false fruit; fleshy thalamus: apple, pear.
• Balausta – juicy testa is edible: pomegranate.

II. Aggregate fruits (Etaerio) – from a multicarpellary apocarpous ovary of a single flower; each free carpel forms a fruitlet:

• Etaerio of achenes – strawberry, Ranunculus; Etaerio of follicles – Michelia, Calotropis; Etaerio of drupes – raspberry; Etaerio of berries – custard apple (Annona squamosa).

III. Composite (multiple) fruits – from a whole inflorescence:

• Sorosis – from a spike, spadix or catkin; flowers fuse with the axis: pineapple (Ananas), jackfruit (Artocarpus), mulberry (Morus).
• Syconus – from a hypanthodium; the hollow fleshy receptacle encloses many tiny achenes: fig (Ficus carica), peepal, banyan.

5 likely exam questions

Long answer

1. Define placentation. Describe different types of placentation with labelled diagrams and examples. Add a note on cohesion and adhesion of carpels.
2. Define fruit and pericarp. Classify fruits and describe simple dry and fleshy fruits with suitable examples.

Short answer / short notes

3. Differentiate between aggregate and composite fruits with examples.
4. Describe the syconus fruit of Ficus.
5. Write a note on schizocarpic fruits.