Inflorescence , Flower , Fruits

INFLORESCENCE

Arrangement of flower on floral axis is called inflorescence.

Racemose – In this type of inflorescence the main axis continues to grow and does not terminate in a flower and give off flowers laterally in acropetal manner (Where old flowers are arranged lower side and young flowers are upper side).

This is of foll. diff. types :

Raceme -  When peduncle or (main axis) is elongated and flowers are pedicellate. Eg. Radish. When peduncle is branched and each branch bear pedicelated flowers like racemose and are arranged in acropetal manner known as compound raceme or panicle Eg. Gulmohar, Neem.

Spike – In it peduncle is elongated but flowers are sessile. Eg. Achyranthes. When peduncle is branched and each branch bear spike, like inflorescence then the small branch having flower is called spikelet and this arrangement is called as spike of spike of spikelet. Eg. In the members of grass family (Gramineae) wheat

Catkin – In it peduncle is thin, long and weak, and flowers are sessile and unisexual Eg. Mulberry, Betula, Oak.

Spadix - In it peduncle is thick, long and fleshy and have small sessile and unisexual flowers covered with oneor more green or colourfull bracts. Eg. Colocasia, Maize, Aroids, Palms, Grain of maize is fruit long filamentous threads protruding at the end of a young cob of maize are styles.

Corymb –  In it peduncle is short and all flowers are present at same level because the lower flower has much long pedicel than the upper one. Eg. Candytuft (Iberis amara) It in this type of inflorescence peduncle is branched, then each branch has flower cluster then this type of inflores- cence is called compound Corymb.

Umbel – An inflorescence in which the flower stalks of more or less equal length, arise from the same point, At the base of flowers stalk, there is whorl of bracts forming the involucre. Eg. Cantella.

If in this type of inflorescence, peduncle is branched then each branch has flower cluster then this type of inflorescence is called compound umbel. Eg.  Coriander, Foeniculum , cuminum.

Capitulum/Racemose head – In it the growth of peduncle is retarded and it become broad, flattened concave or convex. On it small flowers are found. These flowers are called floret.

If all the flower of Capitulum are same, then it is called monogamous. If the younger flower are present towards centre and older towards the periphery, than it is known centripetal order. The flowers which are present in centre called disc floret and flowers at periphery are called as ray floret and arrangement of this type is called heterogamous. In this type of inflorescence florets may be unisexual, bisexual and sterile. This inflorescence is surrounded by one or more involucre. It is most advanced type of inflorescence, because all flowers are pollinated at same time. Eg. Sunflower, Zinnia, Marigold.

CYMOSE

In this type of inflorescence, the peduncle terminate in a flower. In it the older flowers are present at upper portion and young buds are arragned towards base. This arrangement is called basipetal succession. It is of following types –

Uniparous cyme/Monochasial cyme – The peduncle ending in a flower producing lateral branch at a time ending in a flower. It is two types –

(a)       Helicoid cyme – When all lateral branches developed on the same side on peduncle then it is called helical cyme. Eg. Heliotropism

(b)       Scorpioid cyme - In it the lateral branch is develop on one side and the other branch will develop opposite to first one, i.e. they lie alternate to each other. Eg. Begonia

Dichasial or biparous cyme – In it peduncle ends in a flower from the basal part of peduncle two lateral branches arise which also end in a flower now this same arrangement occur on these lateral branches. Eg. Bougainvillea, Jasmine, Teak

Multiparous cyme/Polychasial – In it peduncle ends in a flower and from the base of it many lateral branches arise, which also terminated in flower, this arrangement now also occur on these lateral branches Eg. Calotropis (madar) , Nerium, Asclepias

SPECIAL TYPE OF INFLORESCENCE –

Cyathium –  The bracts or the involucre become fused to form a cup shaped structure on the margin of it secretory glands are found. In the central part of cup shaped structure a female flowers is found, which mature earlier. Due to the growth of pedicel this come out from the cup shaped structure. Female flowers are surrounded by small male flowers. These are also found on Pedicel. The male flower, which lie toward centre mature earlier than the flowers which are towards periphery.

This inflorescence is found in Euphorbiaceae family like Euphorbia, Poinsetia, Pedilanthus.

Verticillaster – This type inflorescence is found in Labiatae/Lamiaceae family. In this type of inflorescence leaves are arranged in opposite manner on stem. Form the axil of each leaf inflorescence develops. From the main axil, lateral axil arises, on which flowers are found. Now from these branches lateral branches developed also. On these branches flowers are found also. In this inflorescence each dichasial chyme changes into Monochasial (Scorpioid) cyme. Eg. Salvia, Ocimum, Coleus

Hypanthodium – In the peduncle is modified in narrow cup like structure. At the base of cup female flowers develop while towards mouth male flowers develops. All three types of flowers are present in this inflorescence. Eg. Banyan, Peepal, Syconus, Ficus species

Mixed inflorescence – Some times flowers are arranged in both racemose and cymose manner on same peduncle called mixed inflorescence.

(i)        Mixed spadix –Banana

(ii)       Cymose raceme or thyrsus – Grapes.

(iii)     Corymbose raceme – The yound flowers appear to be arranged like corymb but in mature state the longer pedicels of the lower flowers do not bring them to the level of upper ones. Eg. Mustard

FLOWER

It can be defined as modified dwarf shoot which is meant for sexual reproduction. It is characteristics feature of angiosperm whease reproductive organs have been aggregated as flowers.

Parts of a typical flower : It comprises a stalk called pedicel which arises in the axis of leaves called bracts. Upon the pedicel there may be one to many small scaly structures called bracteoles. The terminal part of the pedicel is the thalamus or torus. It is a modified and condensed axis of the flower. Modified leaves called floral leaves or floral parts arises from the nodes of the thalamus as successive whorls. A typical flower of an angiosperm consists of four types of floral parts namely calyx, corolla, androecium and gynoecium.

(i) Calyx : It is the outermost whorl composed of sepals.

(ii) Corolla : It is composed of petals and is the second whorl.

(iii) Androecium : It is the third whorl composed of stamens.

(iv) Gyneocium : It is the innermost whorl and is also called pistil. It shows carpels.

General description of a flower : The flowers are termed pedicellate if they possess stalks and sessile if they lack them. The flower may be described as complete if it bears all the floral parts and incomplete, when one or more floral parts are absent. Flowers are called bisexual if they bear both androecium and gynoecium. The unisexual flowers have either androecium or gynoecium. The unisexual flowers may be male flowers or female flowers. The male flower are also called staminate flowers as they have stamens only. The female flowers have only the carpels and hence called pistillate flowers. Flowers with sterile sex organs are described as neutral flowers. According to the distribution of male, female and bisexual flowers, various pattern are recognized.

(i) Monoecious : Presence of male and female flowers on the same plant, e.g., Acalypha, Cocos and Ricinus.

(ii) Dioecious : Presence of male and female flowers on different plants, namely, male plants and female plants. e.g., Cycas, Carica papaya and Vallisneria.

(iii) Polygamous : Presence of unisexual and bisexual flowers on the same plant, e.g., Mangifera and Polygonum.

Symmetry of flower : The number, shape, size and arrangement of floral organs in a flower determines its symmetry. On the basis of symmetry flowers can be of the following types :

(i) Actinomorphic (Regular = Symmetrical) : Actinomorphic flowers can be divided (passing through center) by any vertical plane in to two equal and similar halves. e.g., Mustard, Brinjal, Catharanthus roseus.

(ii) Zygomorphic (Monosymmetrical) : Zygomorphic flowers can be divide into two equal halves by only one verticle division e.g., Pea, Larkspur, Ocimum.

(iii) Asymmetrical (Irregular) : Asymmetrical flowers can not be divided into two equal halves by any vertical division. e.g., Canna, Orchids.

Arrangement of floral organs :

On the basis of arrangement of floral organs, three types of flowers are recognized. They are :

(i) Acyclic : Here the thalamus is conical or convex and the floral parts are spirally arranged, e.g., water lily and Magnolia.

(ii) Cyclic : Here the floral organs are arranged in regular whorls at the nodes of the thalamus, e.g., Hibiscus and Datura.

(iii) Hemicyclic (Spirocyclic) : Here some floral parts (sepals and petals) are arranged in regular whorls and the remaining parts (stamens and carpels) are arranged spirally. e.g., Annona  and Polyalthia.

Number of floral parts in whorl is called the merosity. There are two kinds of flowers based on the merosity of the flower. They are isomerous flowers and anisomerous flowers.

If the number of sepals, petals, stamens and carpels of flower is equal, such flowers are called isomerous flowers.

Dimerous : Two floral parts in each whorl.

Trimerous : Three floral parts in each whorl.

Tetramerous : Four floral parts in each whorl.

Pentamerous : Five floral parts in each whorl.

A flower with different number of floral parts in each whorl is called anisomerous flower. The sepals, petals, stamens and carpels present at different whorls of a flower vary in their numbers. These are also called heteromerous flowers.

Detailed structure of flower : Angiospermic flowers exhibit many variations in their external morphological characters. Detailed description of a flower helps in its proper identification.

(i) Bract : Bract (hypsophyll) is a small leaf like structure on the peduncle which produces a flower in its axil. The floral buds are usually protected by the bracts. Flower with a bract is described as bracteate and the flower without a bract is known as ebracteate. Bracteoles are small scale like structures present on the pedicel. Bracts are modified into following structures :

(a) Foliaceous bract : Leaf like, expanded green bract is called the foliaceous bract, e.g., Pisum, Lathyrus, Adathoda and Gynandropsis.

(b) Spathe : A large modified bract which encloses spadix inflorescence totally or partially. It may be leathery or woody, e.g., Alocasia, Cocoa, Musa and Typhonium.

(c) Petaloid bract : Brightly coloured petal like bract is known as petaloid bract, e.g., Bougainvillea, Poinsettia and Euphorbia.

(d) Involucre : One or two whorls of green bracts that protect young inflorescence is called involucre, e.g., Coriandrum, Tagetes and Heracleum.

(e) Epicalyx : Whorl of bracteoles present below the calyx or outside the calyx, e.g., Hibiscus rosa sinensis and Malvaviscus arborcus.

(f) Scaly bracts : Reduced, membranous, scale like bracts seen in head inflorescence, e.g., florets in Tridax and Helianthus.

(g) Glumes : The bracts found on the rachilla of spikelet are called glumes. They may be sterile glumes or fertile glumes (lemma), e.g., Oryza sativa.

(ii) Thalamus : The terminal part of the pedicel is called thalamus or torus or receptacle. It is a condensed axis of the flower from which all floral parts arise. Depending upon the position of gynoecium on the thalamus with respect to other parts, flowers are of three kinds – hypogynous, perigynous and epigynous

In many flowers, the thalamus is condensed and the internodes are not seen clearly. But there are some flowers with elongated, distinct floral internodes as mentioned below :

(a) Anthophore : This is the first elongated internode between the calyx and corolla, e.g., Silene, Pennsylvania and Lychnis.

(b) Androphore : It is the second elongated internode between corolla and androecium, e.g., Gynandropsis.

(c) Gynophore : It is the third elongated internode between androecium and gynoecium e.g., Capparis and Gynandropsis.

(d) Gynandrophore : It is an elongated stalk like part between non essential and essential organs of the flower. It is equivalent to androphore, e.g., Passiflora.

(e) Carpophore : This is a stalk like connection present between two carpels. It is formed due to expansion of the thalamus between the carpels, e.g., Coriandrum and Foeniculum.

(iii) Perianth : The non essential organs, calyx and corolla are together called perianth. The perianth protects the stamens and carpels. In angiospermic flowers, the perianth exists in different forms.

(a) Achlamydeous : Perianth is absent and the flowers appear naked. Mostly the achlamydeous flowers occur in cyathium inflorescence. e.g., Euphorbia, Poinsettia.

(b) Chlamydeous : Perianth is present and the flowers usually appear attractive. The chlamydeous flowers are of two types. They are :

Monochlamydeous flowers are with perianth in one whorl, e.g., Amaranthus and Ricinus.

Dichlamydeous flowers are with perianth differentiated into calyx and corolla. They are arranged in two different whorls. The dichlamydeous condition is of two types :

Homochlamydeous : The two whorl or the perianth (calyx and corolla) are similar in all respects and are not identified by different colours, e.g., Michelia.

Heterochlamyoeous : The two whorls of the perianth are dissimilar in many respects. The outer whorl consists of small, green sepals and the inner whorl with large variously coloured petals, e.g., Datura and Hibisus. The term “tepals” is used to describe the perianth lobes which appear like petals, e.g., most of the monocots.

(iv) Calyx : It is the outermost whorl of the flower. It consist of sepals. Usually, the sepals are small and green. They protect other floral organs when the flower is in bud condition. The calyx is described as polysepalous when the sepals are free (e.g., Anona, Tomato) and gamosepalous when the sepals are united (e.g., Datura and Hibiscus). If sepals are fused less than half of the length of calyx tube it is called as partite and if the fusion of sepals is very little, just at the base of calyx tube, it is said to be connate. The sepals may be deciduous or persistent. Usually the persistent calyx do not show any growth after fertilization. Such a calyx is termed as marcescent (e.g., Brinjal, Chillis). Sometimes the persistent calyx shows continuous growth even after, fertilization. This type of calyx called acrescent (e.g., Physalis and Shorea).

In some plants a whorl of green sepals like structure is present at the base of calyx called epicalyx. Epicalyx is considered a whorl of the bracteoles and mostly found in the flowers of family Malvaceae (Althaea, Cotton). The calyx may show number of modifications. They are :

(a) Campanulate : Bell shaped, e.g., Althaea.

(b) Cupulate : Cup like, e.g., Gossypium. 

(c) Urceolate : Urn shaped, e.g., Hyoscyamus.

(d) Infundibuliform : Funnel shaped, e.g., Atropa belladona.

(e) Tubular : Calyx tube like, e.g., Datura.

(f) Bilabiate : Calyx forms two lips, e.g., Ocimum.

(g) Spurred : One or two sepals forming a beak like structure, e.g., Larkspur.

(h) Pappus : Calyx are modified into hairs e.g., Sonchus, Tridax (Asteraceae).

(i) Spinous : When calyx forms spines, e.g., Trapa.

(j) Hooded : When sepals enlarged to form a hood over the flower, e.g., Aconitum.

(k) Petaloid : Enlarged and brightly coloured sepals, e.g., Clerodendron, Mussaenda, Sterculia, Caesalpinia and Saraca.

(v) Corolla : It is the second whorl of the flower consisting of petals. Usually the petals are brightly coloured and scented. They attract the insects which act as agents for pollination. The corolla may be polypetalous (with free petals), gamopetalous (with united petals) or apetalous (without petals). The corolla may undergo modifications or possess some special appendages.

Sepaloid : Green or dull coloured sepal. e.g., Anona, Polyalthia and Artabotrys.

Saccate : The corolla tube may form a pouch on one side. e.g., Antirrhinum.

Spurred : Sometimes one or two petals or the entire corolla tube grow downwards forming a spur that usually stores nectar. e.g., Aquilegia vulgaris.

Corona : Special appendages of different kinds like scales, hairs develop from the corolla. Such appendages are called corona. e.g., Passiflora, Oleander and Nerium.

Forms of corolla : Both polypetalous and gamopetalous corolla exhibit great variation in their forms. It is following types :

(a) Polypetalous corolla : They are of following types :

17. Cruciform : Four free clawed petals arranged in the form of a cross, e.g., Mustard and Radish.
17. Rosaceous : Five free sessile petals withlobes spreading outwards, e.g., Rose, Hibiscus.
17. Caryophyllaceous : Five free clawed petals with limbs at right angles to the claw, e.g., Dianthus.
17. Papillionaceous : Five free unequal petal arranged in definite fashion. The posterior petal is largest and is called standard vexillum. On either side of the standard, two lateral petals unite called wings are present. The remaining two anterior petals to form a boat shaped structure called the keel. e.g., plants of papillionaceae.

(b) Gamopetalous corolla : They are of following types :

17. Tubular : Five united petals form a cylindrical tubular structure, e.g., disc florets of Asteraceae.
17. Infundibuliform : It is a funnel shaped corolla, e.g., Datura.
17. Companulate : It is bell shaped corolla, e.g., Thevetia.
17. Rotate : Short tubular corolla with spread out lobes appearing like a wheel e.g., Brinjal.
17. Hypocrateriform : It is a salver shaped corolla. It is provided with a elongated narrow tube having lobes at the top placed at right angles, e.g., Vinca.
17. Ligulate : Corolla with a short tube which is drawn out into a tongue shaped structure e.g., ray florets of Asteraceae.
17. Bilabiate : The irregular corolla is united, in such a way that it appears two lipped. It is the characteristic corolla of labiatae, e.g., Leucas.

(vi) Aestivation :The arrangement of sepals and petals in bud condition of the flower is called “aestivation”. It is may be of following types :

(a) Open : If the margins of perianth members in a whorl are free with wide gap between them, then the type of aestivation is called ‘open’, e.g., sepals of Mustard.

(b) Valvate : Here the edges of perianth members in a whorl are very nearly touching each other bud do not overlap, e.g., calyx and corolla in Annona.

(c) Twisted : In this type, the perianth members of a whorl show one edge outside and one edge inside. Thus they regularly overlap the neighbouring members on one side. The twisted aestivation is also called contorted or convolute aestivation, e.g., corolla of Hibiscus.  

(d) Imbricate : Here in a whorl of perianth members, one is completely inside and another is completely outside. The remaining perianth members show one edge inside and the other edge outside. The imbricate aestivation is of two types, namely, descending imbricate and ascending imbricate.

Descending imbricate : Here the odd petal is posterior and completely outside. The anterior pair of petals are completely inside. The remaining petals show regular overlapping in the descending manner. It is also called vexillary aestivation, e.g., Tephrosia, Crotalaria and Dolichos.

Ascending imbricate : Here the odd petal is posterior and completely inside. One of the anterior petals is completely outside. The remaining petals show regular overlapping in ascending manner, e.g., Cassia and Delonix.

Quincuncial : In this type, out of the five perianth members in a whorl two are completely outside, two are completely inside and the remaining has one edge outside and one-edge inside. This is confined to pentamerous flowers only, e.g., sepals of Ipomoea, Vinca and Thevetia.

(vii) Androecium : It is the third whorl of a flower consisting of stamens or microsporophylls. Fertile stamens produce pollen grains. Staminodes are the sterile stamens. Petaloid stamens are brightly coloured and appear like petals, e.g., Canna.

(a) Structure of stamen : A stamen shows a long or short stalk called the filament. The filament ends with a terminal fertile part known as the anther. It encloses microsporangia within which microspores or pollen grains are produced. The filament of the stamen is connected to the anther by means of a “connective”. The anther may be monothecous or dithecous. The monothecous anther has only one sac. It is bilocular or bisporangiate, e.g., Hibiscus. The dithecous anther consists of two sacs and is tetralocular or tetrasporangiate in as Datura.

When the face of anther is towards centre of flower it is called introrse e.g., tomato when it is towards the periphery it is called extrorse e.g., Ranunculus.

(b) Fixation : The mode of attachment of a filament to anther by connective is called fixation. It is of following types :

Adnate : Filament attached to the total length of the anther on the back. e.g., Michelia (Campa).

Basifixed : Filament is attached to the base of the anther e.g., Datura, Mustard, Radish.

Dorsifixed : Filament is attached to the anther on the dorsal side at middle portion e.g., Passiflora.

Versatile : Filament is attached to the anther at a point so that anther can swing freely in all direction. e.g., Grasses.

(c) Length of stamens : Based on the relative lengths of the stamens, the conditions of androecium varies :

Didynamous : When there are four stamens in a flower of which two are long and two are short, the condition is described as didynamous, e.g., Ocimum.

Tetradynamous : Out of the six stamens that are found in a flower, four stamens are long and the two are short. This condition is called tetradynamous, e.g., Raphanus and Brassica.

The stamens are described as inserted when they do not extend beyond the petals or corolla tube (Dolichos). When the stamens extend beyond the petals or corolla tube, the stamens are known as (Acacia).

(d) Insertion of stamens : Based on the insertion of stamens, the condition of androecium varies :    

Isostemonous : When the stamen form a single whole and the number of stamen is the same as that of sepals and petals, the flower is isostemonous.

Diplostemonous : Sometimes there are two whorls of stamens. The first whorl alternating with petals (antisepalous) and the second whorl alternating with sepals (antipetalous).

Obdiplostemonous : In this condition first whorl is antipetalous and the second whorl is antisepalous. 

(e) Union of stamens : The union of stamens takes place either among themselves (cohesion) or with other whorls (adhesion).

Cohesion of stamen : Usually three types of cohesion among stamens occur. They are :

Adelphy : When the filaments of stamens are united and the anthers remain free. It is of three types :

Monadelphous : All filaments unite to form a single bundle e.g., Family malvaceae (Hibiscus).

Diadelphous : Filaments unite to form two bundles. e.g., family papilionaceae (Pisum, Sesbania, Tephrosia).

Polyadelphous : Filaments unite to form many bundles. e.g., family rutaceae (Citrus, Melaleuca).

Syngenesious : When the anther of filament are united and the filaments remain free. e.g., Tridax, Sunflower etc.

Synandrous : Here all stamens of a flower are united completely to form a single structure. e.g., family Cucurbitaceae.

Adhesion of stamens : Stamens may unite with other floral organs like sepals, petals or gynoecium. Based on the floral organ involved in the union with stamens, the adhesion may be of the following types :

Epiphyllous : Stamens unite with perianth. e.g., Asperagus.

Episepalous : Stamens unite with sepals.

Epipetalous : Stamens unite with petals. e.g., Datura.

Gynandrous : Stamens unite with gynoecium. It is also called gynandrium or gynostegium. e.g., Calotropis.

(viii) Gynoecium : The gynoecium or pistil is the fourth essential whorl of female reproductive part of the flower and may be made up of one or more carpels (megasporophylls). A carpel has three distinct part, namely ovary, style and stigma. The lower most swollen fertile part of the carpel is the ovary. It encloses ovules. Above the ovary elongated thread like structure attached to the apex of the ovary, the style. The style end with a round, sticky stigma. A sterile pistil is known pistillode. The number of carpels is a gynoecium vary in different flowers. Accordingly the gynoecium may be described as follows :

(a) Monocarpellary : It is a ovary with a single carpel, e.g., Bean.

(b) Bicarpellary : It is presence of two carpels in a ovary, e.g., Helianthus.

(c) Tricarpellary : It is presence of three carpels, e.g., Cocos.

(d) Tetracarpellary : It is presence of four carpels, e.g., Cotton.

(e) Pentacarpellary : It is presence of five carpels, e.g., Hibiscus.

(f) Multicarpellary : It is presence of many carpels, e.g., Annona.

When the number of carpels in a gynoecium are two or more, they may be free or united. If they are free it is called apocarpous gynoecium and if they are fused it is called syncarpous gynoecium.

The ovary encloses one to many chambers called the locules. Usually the number of locules in a syncarpous ovary corresponds to the number of carpels. Sometimes, the number of locules may be doubled. e.g., in Datura, the gynoecium is bicarpellary syncarpous with four locules in the ovary. Based on the number of locules, the ovary may be described as follows Unilocular : Ovary with one locule. e.g., Dolichos.

Bilocular : Ovary with two locules. e.g., Solanum.

Trilocular : Ovary with three locules. e.g., Allium.

Tetralocular : Ovary with four locules. e.g., Datura.

Pentalocular : Ovary with five locules. e.g., Hibiscus.

Multilocular : Ovary with many locules. e.g., Abutilon.

(ix) Style : The stalk like structure present above the ovary is called the style. The style may be long (Datura) or short (grasses) or absent (Papaver). In the family umbelliferae (apiaceae) the base of the style is swollen and forms a structure called stylopodium. There are three types of styles as described below :

(a) Terminal style : If the style arises from terminal part of the ovary, it is called terminal style, e.g., Datura, Hibiscus and Solanum.

(b) Lateral style : If the style arises from one side of the ovary, it is called lateral style, e.g., mango.

(c) Gynobasic style : If the style arises from the base of the ovary it is called gynobasic style, e.g., Ocimum, Salvia.

(xi) Stigma : The terminal receptive portion of the style is called the stigma. It receptive pollen grain during pollination. Usually the lobes of the stigma corresponds to the number of carpels. Accordingly the stigma may be unifid, bifid, trifid, tetrafid, pentafid or multifid.

Capitate : Round stigma. e.g., Hibiscus.

Forked : Divided stigma. e.g., Tridex.

Feathery : Brush like stigma. e.g., Grasses.

(xii) Floral formula : It is an expression summarizing the informations given in a floral diagram. It represents the informations given in a floral diagram in the form of an equation. Following symbols are used in constructing a floral formula.

(xiii) Floral diagram : Diagram illustrating the relative position and number of parts in each of the sets of organs comprising a flower. Floral diagram is usually drawn with reference to mother axis. Following signs are used in constructing a floral diagram

PLACENTATION:

The ovules are attached on ovary walls on one or more cushion called placenta. The manner in which placenta are arranged on ovary wall is known as placentation. It is of following types :

Marginal: This type of placentation is found in monocarpellary gynoecium the placenta develops along the junction of two fused margins. Eg. Pea and other leguminous plants.

Parietal: This type of placentation is fond in unilocular syncarpous ovary. In it, the ovule is formed by the fusion of two or more carpels by their adjacent margins and two or more placenta forms. In this type of placentation, the no. of placenta is equal to no. of carples Eg. Cucurbita, Argemone, and Cruciferae family (Mustard)

Axile: It is found in multicarpellary syncarpous gynoecium. The fusing margin of carpels grows inward and meet in the centre of the ovary. Thus an axis forms in the centre of ovary, thus ovary becomes multichambered. The ovules are born on the central axis Number of these chambers are equal to the number of carpel. Eg. Potato, China rose, Onion. Lemon, Orange, Tomato.

Free central: This type of placentation is found in syncarpous gynoecium. In it, the ovary is unilocular and the ovules are borne on the axis in the centre of the ovary.

Placentation is axile in beginning. After sometime walls of chamber destroy and only ovulated central axis left. eg. Primrose Dianthus (Caryophyllaceae)

Superficial – This type of placentation is found in multicarpellary syncarpous gynoecium. The ovules are attached on the walls of loculii Eg. Nymphaea (Water lily)

Basal: The ovary is unilocular and a single ovule is borne at the base of ovary. Eg. Marigold, Sunflower (Asteraceae family). The seeds are protected inside fruit. But in some fruits, seeds are not found like in grapes, banana and such type of fruits are called parthenocarpic or seedless fruit.

Pericarp : After ripening, the ovarian wall changes into pericarp. This pericarp may be thick and fleshy or thick and hard or thin and soft.

Pericarp is made up of 3 layers :-

(a)   Outermost layer           =   Epicarp

(b)   Middle layer      =   Mesocarp

(c)    Inner most layer          =   Endocarp

(a)       Epicarp – It is the outermost layer it is thin and hard or soft part. It forms outermost layer of fruit which is also called rind

(b)       Mesocarp : It is the middle layer which is thick and fleshy in mango, peach, date palm. In coconut, this layer is made up of fibres which is also called coir

 (c)      Endocarp : It forms the innermost layer it may be thin membrane (eg. Orange, datepalm)  or thick and hard (eg. Mango, Coconut)

TRUE FRUIT :When the fruit is developed only from the ovary, the fruit is called as true fruit. Eg. Mango, Coconut, Zizyphus

FALSE FRUIT OR PSEUDOCARP : In some fruits, in place of ovary, some other parts of flower like thalamus, inflorescence, calyx are modified to from a part of fruit. These types of fruit are called false fruits. Eg. Apple, Strawberry.

CLASSIFICATION OF FRUITS :

(1)  Carpels present in gynoecium are whether free or in fused state.

(2)  One or more flower takes part in formation of fruit.

On the above two basis, fruits are divided into :

(1)   Simple   (2)   Aggregate         (3)  Composite

Simple fruit : These fruit develop from monocarpellary ovary or multicarpellary syncarpous

ovary and only one fruit is formed by the gynoecium. Simple fruits are of two types :

(a)  Fleshy fruit         (b)  Dry fruit

(a)  Fleshy fruit : In fleshy fruit, fruit wall is differentiated into epicard, Mesocarp and endocarp. These fruit develop from superior or inferior syncarpous gynoecium. These may be unilocular or multilocular, these fruits are indehiscent. Dispersal of fruit occurs after pericarp is destroyed. In this fruits pericarp is distinguished into Epicarp, Mesocarp and endocarp.

Fleshy fruits are of following types :

(1) Drupe fruit : These fruit develops from mono or multicarpellary, syncarpous, superior ovary. In these fruits endocarp is hard and stony so these fruits are also called stony fruits. Eg. Mango, coconut, almond, peach walnut, plum. In mango the outermost cover or rind is called epiccarp. Edible fleshy part is Mesocarp and the part where seed is protected is called as endocarp. Epicarp and Mesocarp both are edible part while endocarp is drupe. The rind of Almond and walnut are endocarp and their edible part is seed. In coconut Epicarp is hard and thin while Mesocarp is thick and consists, of hard fibres. The endocarp is hard and seed is proteced in it. The sweet water and of coconut are liquid and solid endosperm.

(2) Berry : These fruits develop from mono or multicarpellary syncarpous ovary. Ovary may be superior or inferior. Placentation is axile or parietal. In these Epicarp is thin like membrane and seeds are embedded in fleshy part initially seeds are attached with placenta of fruit but after maturation these seeds are detached with placenta and are spread randomly in fleshy part.

(i)  Plants with superior ovary = Tomato, Grapes, Brinjal.

(ii) Plants with inferior ovary = Guava, Banana

Date palm is one seeded berry. In it pericarp is divided into Epicarp, Mesocarp and endocarp. Epicarp is thin and soft while Mesocarp is thick and fleshy and endocarp is thin like a membrane. Which is attached with seed.

Arecanut is one seeded fibrous fruit. When its thick fibrous layer is removed then seed comes out which is hard.

(3) Pepo: These fruit develops from tricarpellary, syncarpous and inferior ovary. This fruit is unilocular and have parietal placentation. These fruits are fleshy and spongy. Eg. fruits of Cucurbitaceae family like cucumber, melon, Cucurbita maxima, bitter gourd, muskmelon.

(4) Pome : This fruit develops from bi or multicarpellary syncarpous inferior ovary. The rind and sponge are made up of thalamus. The main part of ovary is like to cartilage. It means it is hard and dry remain inside the fruit seeds are present in it. Eg. Apple, Pear. These are false fruits. Fleshy swollen thalamus of these fruits is edible part.

 (5) Hesperidium : This fruit develops from multicarpellary, syncarpous, superior ovary. This fruit is specialy found in plants of Rutaceae family. Eg. Orange, Lemon.Epicarp of these is made up of thick rind which is leathery and many oil glands are found in it. Mesocarp is the white fibrous structure which is attached with epicarp. Membranous endocarp projects inward and formed many chambers. Many glandular hairs are present on the inner side of endocarp. These glandular hairs are only edible parts.

(6) Balausta :  It is a multilocular multiseeds fruit, which develops from inferior ovary. It’s pericarp is hard. Calyx is persistent which is arranged in the form of crown. If is persistent Carpels are arranged systematically. Seeds are irregularly arranged on placenta. Endocarp is hard. Testa is fleshy and Juiceous. This is the edible part of fruit. Eg. Pomegranate (Punica granatum).

(7) Amphisarca :  This fruit is multicarpellary and multichambered which develops from supericarp is hard and fleshy placenta is found in them. The inner part of pericarp and placenta is edible part of fruit. Eg. wood apple (Aegle marmelos), elephant apple.

SIMPLE DRY-FRUIT

Pericarp of simple dry fruits is hard dry and not differentiated into epicarp, Mesocarp and endocarp. Such fruits are called dry fruit. In some dry fruits, this pericarp is ruptured and seeds are dispersed. These fruits are called dehiscent fruits. In some fruits, pericarp is divided into one or more seeded segments. Such fruits are called Schizocarpic fruits. In some fruits, pericarp does not dehiscence even after maturing/ripening such fruits are called indehiscent fruits.

Simple dry fruits can be divided into following three groups :

(i)  Indehiscent         (ii)  Dehiscent           (iii)   Schizocarpic

(i)Indehiscent fruits : These simple dry fruits are generally of small size and single seeded.

(i) Cypsela: It is a small, one seeded dry fruit which develops from bicarpellary, syncarpous inferior ovary. In it, pericarp and seed coat are free from each other. In these fruits a bunch of hair is attached with the fruit which is known as Pappus. Pappus helps in fruit dispersal. Pappus is modification of calyx. Eg. mainly Compositae family plants. Eg. sunflower, marigold.

(ii) Caryopsis : These are small, one seeded dry fruits. Which develop from monocarpellary, superior ovary. Pericarp of these fruits is fused with the seed coat and form a joint surface. These fruits are present in family Gramineae. Eg. Wheat, rice, maize etc.

(iii) Achene : These are single seeded fruit Which develops from monocarpellary, superior ovary. Pericarp is free from the seed coat  Eg. Clematis, Mirabilis, Boerhaavia are egs. of single seeded fruit.

(iv) Nut : This is a single seeded fruit which develops from bi or multicarpellary syncarpous superior ovary. In it pericarp is hard and unilocular. Eg. Quercus (oak), Anacardium occidentale (Cashewnut) Trapa, (Water chest-nut), Litchi. In Litchi epicarp and Mesocarp is fused and give leathery appearance. Endocarp is membrane like thin. Outer seed coat grows forms an additional coat around the seed which is called as aril. In mature fruit, this aril is fleshy and is only edible part.

(v) Samara :  These are dry indehiscent one seeded feathery fruit. It develops from bi or tri carpellary, syncarpous and superior ovary. The main character of these fruits is that wing like structure develops from its pericarp which helps in dispersal. Eg. Holoptelia. In Shorea robusta wing develops from calyx instead pericarp and these fruits are called samaroid.

ii. Dehiscent Fruits : After ripening when the pericarp of the fruit become dry and hard than these fruits are called dry fruits when pericarp of such fruits are ruptured and seeds are dispersed outside, then such fruits are called dehiscent fruits. These fruits are mainly of 5 types :

(1) Legume or pods : These fruits develop from monocarpellary, unilocular, superior ovary. It is generally long and multiseeded fruit. Dehiscense of fruit occurs at both sutures i.e. Dorsal and ventral side. Dehiscence start from apex and reaches to basal part. Eg. Pea, Beans. When only one or two seeds are present in fruit, then it is also called as pod.

(2) Follicle : It is also multiseeded fruit which develops from superior unilocular, monocarpellary ovary but the dehiscence of it occur only at ventral suture. Eg. Asclepias, Rauwolfia Perivmble or Vinca, Michelia (Champa) Delphinium.

(3) Siliqua : This fruit develops from bicarpellary, ,syncarpous superior ovary and ovary has parietal placentation. Dehiscence occurs at both dorsal and ventral suture and starts from lower part and proceeds upward. Due to false septum ovary become bilocular. On false septum, seeds are attached. This type of fruit is found in Cruciferae family. Eg. Brassica, Mustard.

(4) Silicula : It is reduced form of Siliqua. It’s dehiscense is similar to Siliqua. It is also found in Cruciferae family. Eg. Candytuft (Iberis amara)

(5) Capsule : This is dry multichambered and multiseeded fruit and develop from multicarpellary,syncarpous, superior ovary. In it, Axile placentation is found and dehiscence occurs by various methods. Poricidal (Porous), loculicidal, seotifragal, septicidal.

Eg. Papaver (Poppy), Gossypium (Cotton) Datura, Hibiscus (Lady finger)

iii. Schizocarpic fruit :  It is a multiseeded fruit. After ripening , it is devided into mericarp and seeds come out sometimes after destruction of pericarp seed comes out. The fruits develop from mono or bi or multicarpellary superior or inferior ovary. The mericarp, contains one or two seeds.

Schizocarpic fruits are of four types :-

(1) Lomentum : It develops like the legume. These are bisutural fruits which are constricted or divided in one seeded mericarp, after maturity these are separated with each other. Eg. Tamarind, Cassia fistula, Mimosa pudica, Arachis hypogea, Desmodium.

(2) Cremocarp : It is a double seeded fruit and develops from bicarpellary, syncarpous, inferior ovary. It is generally found in umbelliferae family. On maturation, it dehiscence from apex to base in such a way that two mericarp forms and each contain one seed. These mericarp are attached with carpophore. Carpophore is the extended part of receptacle. Eg. Coriander, Daucus, Cuminum, Foeniculum.

(3) Regma : This fruit develops from tri to pentacarpellary, syncarpous, superior ovary. In it 3 to 5 locules are present and its fruit is breaks into 3 to 5 one seeded part. Each part is knows as coccus. At the outer end of pericarp, spines are found. Eg. Euphorbiaceae family (Castor) has three cocii and Geranium has 5 coccus.

(4) Carcerulus : It is a dry fruit which develops from multi carpellary or bicarpellary ,syncarpous, superior ovary. It divides into four one seeded locules. Eg. Ocimum (Basil), Salvia. In hollyhock and abutilon (family Malvaceae), the no. of locules is more than four because it develops from multicarpellary ovary.

(5) Utricle : It is a single seeded fruit which has thin membrane. It dehiscence generally from cap. It develops from bicarpellary,unilocular, syncarpous, superior ovary. Eg. Achyranthes, Amaranthus.

AGGREGATE FRUITS

These fruit develop from multicarpellary apocarpous ovary. Because ovary. Because in apocarpous ovary , each carpel is separated from one another ,therefore it forms a fruitlet. These fruits make a bunch of fruitlets which is known as etaerio.

(1) Etaerio of follicles: Each fruit of etaerio are follicle. Eg. Calotropis Catharanthus, Magnolia. In Calotropis only stigma are fused or jointed in bicarpellary ovary and ovaries of ovoule are separated. It means only two follicles are present in etaerio. In catharanthus and magnolia etaerio develops from many follicles.

(2) Etaerio of achenes: In this aggregate fruit, each fruitlet is an achene. Eg. Rananculus, Strawberry, Rose, Lotus

            In lotus, thalamus become spongy and some achenes are embedded in it. In strawberry, thalamus is fleshy and small achenes are found on its surface. In rose, many achenes are present on a saucer (Cup) like inner surface of thalamus.

(3)       Etaerio of berries : It is an aggregate of small berries. Eg. polyalthia, Annona squamosa (Custard-apple). In etaerio of Anona all the berries are arranged densly on thalamus.

(4)       Etaerio of drupes: In this type of fruit, many small drupes develop from different carpels. Eg. Raspberry In this type carpel of apocarpus ovary form drupe fruit.

COMPOSITE FRUITS

All composite fruits are false fruits. This type of fruit differ from aggregate fruit that in place of single ovary many ovaries and other floral parts combine together to form fruit. In composite fruits, generally whole inflorescence is modified into fruit. These are of two types:

(1) Sorosis : This fruit develops from spike, spadix or catkin inflorescence. Peduncle become thick spongy and woody or spongy sepals of female flower fused with each other resulting a mass is formed by the flowers of a whole inflorescence. eg. : Jack fruit, Kevda (screwpine),

In Jack fruit (Kathal) pistillate flowers are developed around the penducle. In fruit formation pericarp become spongy and fused. Spiny and rough rind is formed by the upper part of ovaries. In Pine apple peduncle bracts and perianth become fleshy. Due to the fusion of perianths of flower a composite fruit is formed. Other growth indicates the flower.

In mulberry perianth becomes fleshy and calyx of every flower becomes thick, sweet and fleshy and are edible.

Syconus : This fruit develops from Hypanthodium inflorescence. Receptacle become hollow having a pore surrounded by small scales. Staminate pistillate flowers are present near the pore and normal pistillate as well as pistillate flowers are present on the lower side. Many achenes develop from the pistillate flower. Eg.  Ficus  species like fig, Peepal

Geocarpic fruit: Underground fruits are called geocarpic fruit. Eg: Arachis

Dispersal of fruits and seeds –

We know that most of the plants do not move from one place to another. They grow, produce flower and fruits while remaining fixed at one and the same place. The seeds falling directly under the mother plant have to germinate and develop under limited food supply and space. To overcome this problem, the fruits and seeds have developed several special devices for wide dispersal. The natural agents like wind, water and animals and even mechanism of dehiscence in some fruits, help the seeds and fruits to disperse from one place to another, and to long distances from the parent plant.

Wind-

In the species where the seeds are light in weight or have some accessory part to help dissemination, are dispersed by the air current. The seeds of Drum-stick and Cinchona, and fruits of yam, maple and sal tree, are provided with one or more appendages in the form of thin, flat and membranous wings, which help them to float in the air and be carried away to long distances. In the members of Asteraceae, the calyx is modified into hair- like structures called pappus. They persist in fruit and open out like umbrella, helping the seeds to float in the air. In poppy and prickly poppy (Argemone), the fruit dehisces and seeds are thrown out to a distances away from the parent plant. The seeds of Calotropis, Alstonia and cotton are provided with hair and cover sufficient distances alongwith the wind. The seeds of orchids and some grasses are very small and light in weight and may be easily carried away by wind to far off places.

Water –

The fruits and seeds with specialized devices which may be in the form of spongy and fibrous outer walls as in coconut and spongy thalamus as in lotus, and small seeds with airy aril as in water lily, float very easily in water and are carried away to long distances with the water current.

Animals –

The fruits and seeds with hooks, spines, bristles, stiff hair, etc. , get attached to the body of hairy and woolly animals and are carried away by them to distant places. For instance fruits of Xanthium and Urena bear curved hooks, spear grass has a bunch of stiff hair, Tribulus has sharp and rigid spines Boerhaavia  has sticky hair, which help their dispersal by animals. The edible fruits like guava, fig and plum are dispersed by birds and even human beings, either by feeding on them and passing out undigested seeds with faces or by carrying them to other places for later feeding.

Defense mechanism in plants –

Nature has provided some specialized structures and organs to plants which save them natural unfavourable factors and from attack of enemies. These specialized structures, organs, substances and adaptations protect the plants from destroying by animals, insects and disease carriers. This is called defence mechanism in plants. Some of these are as follows :

1.         Epidermis, Periderm, cork and bark.

2.         Trichomes, hairs and spines.

3.         Laticiferous glands or ducts.

4.         Secretory glands.

5.         Taste of different plant aprts.

6.         Underground plant parts.

7.         Myrmecophily.

8.         Colour, shape and structure of plants.

1. Epidermis, Periderm, Cork and Bark:

The epidermis is formed by division in the protoderm. Usaully it is single layered but in Vanda (orchid), Nerium, Peperomia  etc. it is multilayred. In Peperomia, it consists of 14 to 15  layers of cells. All parts of a plant except root, have a layer of wax-like substance or cutin on the outer face of the epidermis. This layer is known as the cuticle. In Cycas and Pinus the cuticle is lignified. In some plants it has rod shaped structured and granules. On aerial parts of  Equisetum and members of grass family silica or silicon oxide is found. Similarly on epidermis of some plants wax, oil resin crystallized salts, silica, lignified substances etc. are deposited. Epidermis acts as a protective layer which saves internal tissues from being damaged by high temperature, microbes, acidic rain and high wind velocity etc.

In woody plants Periderm is present which is a secondary epidermal tissue and is formed by activity of the phellogen. Here the cork is a protective layer consisting of prism like tubular cells. Bark is the tertiary epidermal tissue found in woody plants. This layer consists of dead and dried tissues. Its main function is to protect the internal tissues from mechanical injury.

2. Trichomes, Hairs and spines:

Trichomes may be present on vegetative and reproductive parts of plants. These are dead or living and persistent and may show veriable structures and functions. Leafy epidermal hairs regulate atmospheric humidity, covering hairs protect plants from disease causing insects, glandular epidermal hairs secrete some chemical substances and stinging hairs pierce the skin if animals and secrete poisonous substances which cause irritation and protect the plants from animals. Uni-or multicellular sticky glandular hairs secrete some sticky substances.

The stinging hairs of Urtica diocia Consist of a calcified basal part and a narrow siliceous elongated upper part. The lower part is surrounded by collar – like structure formed by outgrowths of the epidermal cells. On contact with an animal the upper part pierces into its skin and secretes histamine and acetylcholine which cause irritation and itching.

Spiny stipules and spines found in xerophytes protect these plants from grazing animals. Spiny stipules of Zizyphus, Acacia, Prosopis juliflora, Balanites, Tribulus etc. and spines of Euphorbia act as defensive devices against grazing animals. Prickles of Capparis, Bombax and rose and needle like hairs of cacti save these plants from animals.

3. Laticiferous glands or Ducts:

Woody plants of torrid and other xeric areas secrete a white milky fluid which is called latex. This substance is secreted by the Laticiferous ducts or glands. Mostly it is white. It is a viscous fluid which contains various substances like water, hydrocarbons, resins, oils, proteins, acids, salts, sugars and rubber in suspended from. It is found in members of family Moraceae, Euphoriaceae, Apocyanaceae etc. Latex helps in protection of these plants from animals. The latex secreted by plants of Calotropis is poisonous.

4. Secretory glands or cells:

These are specialized cells found in ground tissue. These cells are different from other cells in their structure and shape and are called idioblast. They are filled with difference types of excretory of secretory substances such as oils, tannins, gums, mucilage and different types of crustals. Smell of oily substances secreted by oil glands present in the leaves and dark of Eucalyptus and pericarp of lemon fruit protect these plants from animals. Other such examples are Tamarix, Plumbago, Thyus capitatus etc.

5. Taste of difference plant parts :

Aerial parts like fruits, seeds, leaves, branches and bark of some plants contain different types of alkaloids or excretory substances which are repulsive or bitter to taste and are disliked by animals e.g. Azadirachta indica, Momordica charantia, Trigonella, Ocimum sanctum, Datura stramonium, Papaver somniferum, Mentha arvensis, Nicotiana tabacum, Carcia papaya, Cinchona officinalis etc.

6. Underground plants: In some plants remain under the soil i.e. out reach of grazing e.g. underground modified roots of radish (Raphanus sativus), carrot (Daucus carota), turnip (Brassica rapa), Sugarbeet (Ipomea batata), chukandar (Beta vulgaris), heeng (Ferula asafoetida) etc. underground modified stems of potato (Solanum tubersum), arbi (Colocasia antiquorum), onion (Allium cepa), garlic (Allium sativum), ginger (Zingiber officinale), turmeric (Curcuma domestica) etc. and undrgound fruits of ground nut (Arachis hypogea).

7. Myrmecophily :

Gauva (Psidium guajava), mango (Mangifera indica), litchi (Litchi chinensis), shahtoot (Morus alba) etc. secrete some substances which attracts some ants. These ants take their abode on these plants and etc. as bodyguards against any marauding animal. This relationship is called Myrmecophily.

8. Colour, shape and structure of plants :

Certain plants strikingly resemble some dreaded animals so that they are carefully avoided by other animals. This is known as minicry or copying other animals e.g. plants of Caladium and Sensviria resemble spotted serpents.