7 Main Organs of Flowering Plants (With Features)

The following points highlight the seven main organs of flowering plants. The organs are: 1. Roots 2. Stems 3. Leaves 4. Inflorescence 5. Flowers 6. Fruits 7. Seeds.

Organ # 1. Roots:

Roots differ from stems in the absence of nodes and leaves.

Position:

Primary – an extension of the radicle of the embryo.

Secondary – branches of other roots.

Terrestrial – growing in earth.

Aerial – growing in the air.

Adventitious – growing from stems or leaves.

Morphology:

Tap – a main root growing straight downward.

Fascicled – arranged in cluster and approximately equal in size.

Fibrous – slender and usually tough.

Organ # 2. Stems:

Stems produce nodes at more or less regular intervals, with internodes in between. Each node normally bears one or more leaves with a bud in the axil.

Position:

Twig – a short lateral branch of a woody stem.

Decumbent – lying prostrate, with tip turned upward.

Texture:

Herbaceous – die at the end of the season’s growth.

Shrubby – larger than herb lower part woody.

Woody – living over winter and hard in texture.

Specialized stems:

Tendril – a lateral climbing organ.

Prickle – a sharp pointed protective organ.

Cladophyll – a stem having the appearance and function of a leaf.

Surface:

Glaucous – surface smooth and shining.

Glabrous – surface smooth and dull.

Succulent – stem thick and fleshy with reserve food.

Hairy – surface with hairs.

Spiny – surface with spines.

Prickly – surface with prickles.

Shape:

Cylindrical – straight and rounded.

Angular – stem having ridges e.g. in Lamiaceae.

Flattened – stem flat and plate-like.

Buds:

Buds are incipient and unfolded shoots.

Kinds:

Dormant – inactive bud due to seasons i.e. winter or summer.

Floral bud – unopened flowers.

Position:

Terminal – at the end of the shoots and terminating the seasons growth.

Axillary – growing in the axil of a leaf,

Lateral – growing from the side of the stem.

Adventitious – growing from roots or leaves.

Organ # 3. Leaves:

They are always borne on the nodes of stems. These are having primarily the functions of transpiration, respiration and photosynthesis and often specialized for other functions.

Duration:

Deciduous – falling off, soon after maturity.

Persistent – leaves remaining in place and functioning for 1 or more years after formation.

Evergreen – Leaves not deciduous but persistent.

Insertion:

Cauline – leaf borne on the main stem.

Ramal – leaf borne on the branches.

Radical – Leaf borne on reduced stem and appears to come from the root.

Arrangement of leaves on stem or Phyllotaxy (Fig. 21.9):

Alternate – leaves occur single at each node and so arranged that a line drawn on the stem through the leaf bases will take a spiral course up the stem.

Opposite – Two leaves at a node on opposite sides.

Opposite deccusate – The line of insertion of a pair of leaves on the node is at right angles to the line of insertion of the leaves at the next node so that the leaves form four vertical rows on the stem.

Opposite superposed – The line of insertion of a pair of leaves at a node is parallel to the line of insertion of leaves of next lower or upper node so as to form two vertical rows of leaves on the stem.

Whorled – more than two leaves at a node in a circle around it.

Trifoliate – having a whorl of three simple leaves.

Bact – a relatively small leaf just below an inflorescence or flower.

Leaf Parts:

Blade – flat and expanded portion.

Petiole – Leaf stalk.

Stipules – scale-like attachments at the base of the petiole.

Sheath – basal portion of (grass or sedge) leaves surrounding the stem.

Ligule – the extension at the top of the leaf sheath of grasses.

Sessile – leaf without petiole, blade attached directly to the stem.

Exstipulate – leaf without stipules.

Leaf Shape (Fig. 21.4):

Linear – very narrow, without parallel margins.

Lanceolate – narrow and tapering towards the ends.

Oblong – About twice as long as broad.

Reniform – Kidney shaped e.g. Malva.

Cylindrical – Like a cylinder e.g. Onion.

Leaf Margin (Fig. 21.8)

Entire – Without indentation or incisions.

Hairy – Hairs on the margin of the leaves.

Dentate – Margin broken up into small projections and directed outwards.

Spiny – Teeth hard and pointed.

Serrate – Teeth pointing toward the apex.

Undulate – With wavy surface at margin.

Lobed – With relatively few, large, shallow indentations.

Leaf base:

Cuneate – The blade extending downward along the petiole.

Sagittate – The base of the blade extended into two lobes that point downward or slightly inward.

Leaf apex (Fig. 21.5):

Acuminate – With a long, slender, sharp point, the margins near the tip being concave.

Acute – With the point forming an acute angle, the margins near the tip being straight.

Obtuse – Blunt-pointed or rounded.

Mucronate – Leaf with a board apex ending abruptly in a sharp tip.

Emarginate – Leaf with a shallow notch at the tip.

Cuspidate – Terminates into a long sharp, spiny point.

Truncate – Ending abruptly as if cut transversely straight.

Cirrhose – Ending into a tendril like structure.

Retuse – Slightly notched obtuse apex.

Venation (Fig. 21.7):

The arrangement of veins in the leaf blade.

Reticulate or netted – Veins branching and intersecting to form a network.

Parallel – Veins run parallel to each other.

Unicostate – Number of midrib one.

Multicostate – Number of midribs many.

Midrib – A large main vein running lengthwise through the blade from petiole to tip.

Surface coverings:

Glabrous – Without hairs of any kind.

Glaucous – Covered with a whitish waxy coating that easily rubs off.

Pubescent – With fine, soft short hairs.

Villous – With long, silky, straight hairs.

Hispid – With stiff, bristly hairs.

Tomentose – With long, curled, matted hairs.

Types of Leaf (Fig. 21.3):

Compounding – Simple or compound leaf.

Simple – With the blade is in one piece.

Compound – With the blade divided into several distinct parts.

Usually each of these parts or leaflets is attached to the midrib or stalk by a definite articulation.

Pinnate – Having a midrib with smaller veins branching from it.

Paripinnate – Leaflets in pairs, numbers even.

Imparipinnate – All leaflets except terminal one in pairs, number odd.

Bipinnate – Leaflets further divided into leaflets of second order, e.g. Acacia.

Tripinnate – Leaflets divided into leaflets of third order.

Palmate – The main vein radiate from the point where petiole joins the blade.

Bifoliate – Leaf having two leaflets.

Trifoliate – Leaf having three leaflets.

Multifoliate – Leaf having many leaflets.

Leaflet – One of the parts of a compound – leaf blade.

Rachis – The extension of the petiole to which the leaflets of a attached.

Decompound – With leaflets compounds e.g. in Apiaceae.

Organ # 4. Inflorescence:

It is the mode of arrangement of flowers on a plant. An inflorescence is, in reality, a closely branching stem, each branch bearing a flower.

Kinds of inflorescence:

Solitary terminal – Flowers occur singly at the top of a branch.

Solitary axillary – Single flower situated in the axil of a leaf.

Simple – Only the main inflorescence stem, branches.

Compound – Inflorescence stem branches two or more times.

Special – Branching of peduncle.

Racemose or indeterminate – The main axis grows idenfinitely and bear flowers laterally; thus stopping its terminal growth.

Raceme – A central axis bearing pediceled flowers along its sides, the pedicels equal in length when mature.

Spike – A central axis bearing sessile flowers along its sides.

Catkin or ament – Spike bearing apetalous unisexual flowers, usually pendulous.

Corymb – Central axis like raceme but the flowers reach the same level on account of elongation of the pedicel of lower flowers.

Umbel – Flowers pedicelled, attached at the same point on the top of the stem as in Apiaceae (Umbelliferae).

Capitulum or head – Axis of the spike is suppressed to form a flat or convex disc-receptacle; sessile flowers crowded together to form a compact mass. The flowers are of two types i.e. peripheral ray florets and central-disc florets e.g. Asteraceae.

Spadix – A fleshy central axis bearing many male flowers below and many female flowers above. The spadix is surrounded by a large bract or spathe, usually showy, giving the whole the effect of a single flower.

Panicle – Indefinitely branching; long pedicelled; loosely branched compound raceme or corymb.

Cymose or determinate – Lateral branches of the peduncle end in a flower which come to lie opposite the bract as a result of straightening the sympodial axis.

Uniparous – In this the main axis and its successive branches have only one lateral branch terminated by a flower.

Helicoid uniparous cyme – The main axis stops growth after forming a branch on one side. This branch in turn develop another branch on the same side and so on e.g. Solarium and Hamelia.

Scorpioid uniparous cyme – In uniparous cyme when branches develop alternately from the right and the left of the axis e.g. Heliotropium.

Biparous or dischasial cyme – The main axis is terminated by a flower and has two lateral branches also terminated by flowers; each of the latter again bears two branches and this may be repeated two or more times e.g. Nyctanthus.

Multiparous or polychasial cyme – The main axis is terminated by a flower and more than two secondary branches also terminated by flowers, are given off from the main axis as in Calotropis.

Organ # 5. Flowers:

Flowers are important organs of sexual reproduction in plants.

Floral organs:

Receptacle – The expansion at the top of the peduncle that bears the carpels and other floral organs.

Calyx – The collection of sepals that encloses the rest of the organs in bud.

Corolla – The whorl of petals just inside the calyx and usually forming the showy part of flower.

Ligule – Straped shaped extension of the corolla of ray florets in Asteraceae (Compositae). In Poaceae (Gramineae), the collar like extension of the leaf sheath clasping the stem above the attachment of the blade.

Stamen – A microsporophyll found just inside the corolla and producing the pollen grains.

Filament – Stalk of the stamen.

Anther – The microsporangium which contains the pollen grains.

Pistil – Composed of one or more carpels that may be united completely or at the base or free.

Bract – A leaf or scale in whose axil an inflorescence, flower or floral organ is produced.

Spathe – A large, usually showy bract at the base of a spadix or other inflorescence and enclosing it.

Involucre – A series of scale-like leaves at the base of a flower or inflorescence.

Floral symmetry:

Actinomorphic – Flower divisible along two or more planes into many halves which are equal (radial symmetry).

Zygomorphic – Flower divisible into equal halves in one plane only.

Symmetrical – Face of the flower divided by one or more median planes into equal halves.

Asymmetrical – Face of the flower cannot be divided into two equal halves.

Sexuality:

Complete – Containing all the different kinds of floral parts.

Hermaphrodite or bisexual – Both stamens and pistils present.

Unisexual – With stamens or pistil but not both.

Staminate or male – With stamens but not pistils.

Pistillate or female – With pistils but not stamens.

Monoecious – Each individual plant producing both staminate or pistillate flowers.

Dioecious – Each individual plant bearing only staminate or pistillate flowers but not both.

Pollination:

Anemophilous – Adapted for wind pollination.

Entomophilous – Adapted for insect pollination.

Hydrophilous – Adapted for water pollination.

Zoophilous – Adapted for animal pollination.

Insertion:

Hypogynous – Calyx, corolla, and stamens attached to the receptacle at the base of the ovary, which is superior.

Perigynous – Sepals, petals and stamens attached to the margin of a cup-shaped receptacle.

Epigynous – Sepals, petals and stamens apparently growing from the top of the ovary but in reality from the hypanthodium, which extends up around the ovary and adhere to it.

Arrangement of floral parts:

Aestivation – Arrangement of floral parts in the bud (Fig. 21.14)

Valvate – Petals or sepals do not overlap but simply touch or in front each other by their margins.

Twisted or contorted – The sepals or petals overlap the adjacent sepal or petal on one side and is in turn overlapped by another sepal or petal on the other side resulting in a regular one sided twist.

Imbricate – When the margins of the sepals or petals overlap each other in such a way that at least one member of each whorl has both margins covered.

Ascending imbricate – In overlapping one of the sepal or petal is upwards.

Descending imbricate – In overlapping one of the sepal or petal is downwards.

Quincuncial – When two of the sepals or petals have covered margins.

Number of floral parts:

‘Merous’ suffix, taken with a numerical prefix, indicates the number of each of the floral parts, for e.g. 5-merous or pentamerous flower.

Epicalyx – An extra calyx found in some flowers outside the calyx e.g. Malvaceae.

Calyx (Fig. 21.12):

Pappus – Sepals denoted by fine hairs.

Spurred – Two or more sepals united to form a spur.

Bilabiate – Gamosepalous with two lips.

Tubular – Long tube-like.

Gamosepalous – Sepals united.

Sepaloid – Green in colour.

Corolla (Fig. 21.13):

Apetalous – Without petals. Polypetalous – Petals free.

Gamopetalous – Petals united with each other at their margins.

Cruciform – Corolla polypetalous and petals arranged like a cross.

Rosaceous – Corolla polypetalous, petals spreading, unclawed.

Tubular – Tube-like or forming a tube.

Campanulate – Corolla bell shaped.

Infundibuliform – Corolla funnel shaped.

Bilabiate or bilipped – Petals united to form two lips.

Strap-shaped – Corolla gamopetalous; lower portion tubular and upper flat e.g. ray florets in Asteraceae (Compositae).

Corona – Well developed ligular outgrowth on corolla.

Androecium:

Collection of stamens in a flower.

Cohesion of stamens:

Monadelphous – Stamens united into one bundle by filaments.

Diadelphous – Filaments united into two sets.

Polyadelphous – When stamens united by their filaments into more than two bundles.

Syngenesious – When anther lobes are united and their filaments remain free e.g., in family Asteraceae (Compositae).

Adhesion of stamens (Fig. 21.16):

Epipetalous – When stamens attached to the petals.

Gynandrous – When stamens are attached to the gynoecium e.g. Calotropis.

Relative length of stamens:

Didynamous – Stamens of unequal length, two short and two long.

Tetradynamous – Four long and two short stamens.

Introrse – Anther facing the centre of the flower.

Extrorse – Anther facing the priphery of the flower.

Staminode – A sterile stamen.

Fixation of anthers lobes on the filament (Fig. 21.15):

Basifixed – When filament is attached to the base of anther.

Adnate – When filament is attached to the back of the anther throughout its whole length.

Dorsifixed – When filament appears to be inserted at the back of the anther.

Versatile – When the filament is attached to the back of the anther by a fine point so that the anther swings freely e.g. grasses.

Gynoecium or pistil (Fig. 21.17):

Collection of carpels in a flower, whether separate or united.

Simple – When it is composed of a single carpel.

Compound – When it is composed of more than one carpel.

Apocarpous – When carpels are free from one another.

Syncarpous – In compound pistil the carpels are united with one another.

Number of carpels:

Monocarpellary – Pistil composed of single carpel.

Bicarpellary – Pistil composed of two carpels.

Polycarpellary – More than two carpels.

Inferior ovary – Ovary embedded in the receptacle, resulting in an epigynous insertion of petals and stamens.

Superior ovary – Ovary on the top of receptacle, with the insertion of sepals, petals and stamens hypogynous.

Carpel type:

Stylocarpellous – Carpel without a stipe and with a style.

Stylocarpepodic – With a stipe and a style.

Stylodious – With single free carpel.

Synovarious – The condition when the ovaries of adjacent carpels are fused while their styles and stigmas separate.

Synstylovarious – The condition when the ovaries and styles of adjacent carpels are fused while their stigmas separate.

Terete – Cylindrical and elongate.

Semicarpous – With fused ovaries of adjacent carpels and their free styles and stigmas.

Style Type:

Geniculate Style – the style which bents abruptly.

Gynobasic Style – The style which is attached at the base of the ovary in central depression e.g. Lamiaceae.

Heterostylous – With styles of different shapes or lengths.

Homostylous – With styles of same shapes or lengths.

Stigma Type:

Lobed – Stigma having lobes.

Lineate – Linear i.e. in the form of lines.

Discoid – Like a disc.

Plumose – Feather like.

Diffuse – Spread over a wide surface.

Capitate – Like a cap or head.

Clavate – Club-shaped.

Crested – Possessing a terminal tuft or ridge.

Decurrent – Long and extending downward.

Placentation:

The way in which the placentae are arranged is called placentation.

Placentum – Inner surface of the ovary wall on which ovules are borne, usually the margin of carpel.

Marginal – In case of monocarpellary and unilocular ovary, only one placentum develops by the united margins of the single carpel on which ovules attached e.g. Pea, Bean.

Parietal – Each carpel more or less open,-with margins of adjacent ones united, thus forming a one-chambered compound ovary with placentae on the walls at the lines of union.

Axile – Each carpel entirely closed, thus making as many chambers as carpels with the placentae at the center of the pistil.

Free-central – In this case the ovules develop on the central axis of a unilocular gynoecium, the axis not being connected by partitions with the walls of the ovary e.g. Caryophyllaceae.

Basal – When placenta is situated at the base of a unilocular ovary from which a single ovule is developed.

Superficial – When ovary is multilocular and the ovules arise from the partition walls of the chambers e.g. Waterlily.

Ovules:

Orthotropous – Ovules symmetrical and straight with the chalaza at the base and micropyle at the tip.

Anatropous – Ovule symmetrical but completely inverted so that the apparent tip is really the chalaza and the micropyle is close to the stalk, which is adnate to the entire length of ovule.

Amphitrophous – Ovule symmetrical but half inverted, so that the stalk appears to be attached at the side.

Campylotropous – Ovule asymmetrical and curved so as to bring the base and micropyle close together.

Organ # 6. Fruits:

The true fruit is the ripened ovary; it may however have various appendages as receptacle, involucre, calyx, style etc., which are commonly included under the term fruit.

Parts of wall:

Pericarp – Wall of the fruit considered as a whole.

Exocarp – Outer layer of the pericarp including the skin.

Mesocarp – Middle layer of the pericarp.

Endocarp – Inner layer of the pericarp, including the linning wall of the seed chamber.

Character of wall:

Fleshy – Relatively fleshy and juicy.

Dry – Relatively hard and tough.

Kinds of fruit:

Simple – Composed of single ripened ovary.

Aggregate – Composed of several ripened apocarpous ovaries from a single flower, joined together by a common receptacle.

Multiple – Ripened ovaries of several flowers born in a compact spike and joined together at maturity.

Simple one seeded fruit:

Achene – Small dry indehiscent one seeded fruit, seed separating from the ovary wall.

Nut – Like achene, but pericarp hard, tough and woody protecting seed.

Caryopsis – A seed like fruit resembling achene, seed coat firmly united to the wall of ovary.

Samara – Fruit like achene but winged.

Cypsela – At the top of the fruit hair like growth is present.

Simple many seeded:

Pod or legume – Monocarpellary fruit dehiscing along dorsal and ventral suture.

Follicle – Monocarpellate dry fruit, dehiscing along ventral suture.

Siliqua – Long, slender capsule of two carpels, ovary bilocular due to false septum.

Silicula – Like siliqua but short and compressed.

Capsule – A many seeded dry, dehiscent fruit, derived from polycarpellary syncarpous ovary.

Schizocarpic fruits:

Simple many seeded dry fruits which break up on ripening into a number of many one seeded parts. If these one seeded parts are of dehiscent type then they are called cocci and if indehiscent called mericarp.

Lomentum – Many seeded dry fruits, breaking into a number of one seeded parts by transverse septa.

Cremocarp – Arise from bicarpellary syncarpous inferior ovary; on ripening two loculi with one seeded locule separate from each other and keep hanging from the top of central axis called carpophore.

Regma – Fruit break into a number of dehiscent parts called cocci.

Fleshy fruits or succulent fruits:

The fruit wall or pericarp becomes fleshy and full of food material.

Drupe – One seeded, fleshy fruit with hard and stony endocarp fleshy mesocarp and epicarp constitutes the skin.

Berry – Poly car pell ary, many seeded, fleshy fruit with pericarp entirely soft.

Pome – A multi-carpellate, several seeded fruit, in which the wall is a combination of carpels and receptacle.

Hesperidium – Many celled fruit, endocarp projects inwards forming distinct cells or chambers and epicarp and mesocarp fuse to form skin.

Composite fruits or multiple fruits:

Fruits developed from the entire inflorescence.

Sorosis – Develops form spadix. The axis of inflorescence, ovaries, perianth leaves of flowers all grow simultaneously and fuse together to form a fleshy mass.

Syconus – Develops from hypanthodium inflorescence with a hollow fleshy receptacle. It contains within it many small fruits developed from the pistillate flowers of the inflorescence e.g. Fig, Banyan.

Organ # 7. Seeds:

The seed is a ripened ovule.

Parts of seed:

Integument – One of the layers that grows around the megasporangium from its base and from the walls of the ovule and hence the seedcoat.

Testa – Outer covering of seed.

Endosperm – The tissue that stores food outside the embryo. It originates from a union of the second sperm nucleus with the secondary nuclei.

Embryo – Young plant developed from the fertilized egg cell.

Funiculus – Stalk of seed or ovule.

Chalaza – The place where the seed coat unites with the rest of the ovule.

Micropyle – An opening where the integuments have not completely grown over the ovule.

Hilum – The scar on a seed left by its separation from the funiculus.

Tegmen – When there are two seed coats then the inner thin and delicate layer.