About types and parts Fruit

Aug 09, 2022, 16:45 IST

About Fruit

There is dual effect of fertilization on ovary. After syngamy ovule is changed into the seed. Side by side pollen tube triggers some mechanism in the ovary wall which causes production of growth hormone, due to which ovary is changed into the pericarp after ripening.

Fruit may be defined as a mature and ripened ovary. Fruit formed without fertilization is called parthenocarpic or aspermic fruit and this phenomenon is called parthenocarpy or aspermy (F. Nou), e.g., banana, grapes, pineapple, etc. Such fruits do not have seeds.

TRUE AND FALSE FRUITS

In most of the fruits only the ovary takes part in the formation of fruit; such fruits are known as true fruits or eucarp. Sometimes other floral parts such as thalamus (as in apple, pear, fig), calyx (as in pineapple), etc., form a major part of the fruit; such fruits are described as false fruits, accessory fruits or spurious fruits or pseudocarp.The fruit is very useful for plants as it protects the seeds and helps in the dispersal of seeds.

PARTS OF FRUITS

A fruit has two main parts, seeds and pericarp (fruit wall). Seeds are fertilized and ripened ovules. The structure of pericarp varies greatly in different kinds of fruits. Pericarp develops from the wall of the ovary. Depending upon its nature, the fruit is dry or succulent (fleshy pericarp). In fleshy fruits (e.g., peaches, plums, cherries etc.) it is clearly differentiated into three layers- the outer epicarp, the middle mesocarp and the inner endocarp.

TYPES OF FRUITS

On the basis of the number of ovaries involved, fruits are of following three types: simple fruits, aggregate fruits and composite or multiple fruits.

SIMPLE FRUITS

A fruit that develops from a single ovary (either monocarpellary or polycarpellary and syncarpous) of a flower is called simple fruit. Ovary can be simple or compound of all the three groups mentioned above, simple fruits constitute the largest and the most diversified group.

Simple fruits are of two types, dry and fleshy.

DRY FRUITS

The pericarp becomes more or less dry when ripe. The dry fruits are of three types: Capsular fruits (Dehiscent fruits), Achenial fruits and Schizocarpic fruits.

Capsular fruits: Dehiscent fruits burst automatically on ripening, liberating seeds.

Indehiscent fruits or achenial fruit : Indehiscent fruits do not burst automatically on ripening. Their seeds are discharged after the decay of pericarp.

Schizocarpic fruits: Schizocarpic fruits split into a number of indehiscent units called mericarps. But when the broken piece gets dehisced, it is called coccus. Each mericarp contains one seed. However, the pericarp does not burst and seed is liberated only after the decomposition of pericarp. Thus these are intermediate between dehiscent and indehiscent types.

Types of dehiscent or capsular fruits

They are simple dry many seeded dehiscent fruits. Depending upon the mode of dehiscence these are 5 types: Legume or Pod, Follicle, Siliqua, Silicula and Capsule.

Legume or pod: It develops from a monocarpellary, unilocular and superior ovary with marginal placentation. At maturity the fruit dehisces along both the sutures from apex to the base e.g., Pisum (pea), Cicer (gram), etc.

Follicle: The follicle resembles legumes in that it develops from a monocarpellary, unilocular and superior ovary but differs from the legumes in that it splits open at maturity along one suture, i.e., ventral suture, e.g.. Larkspur, Calotropis (madar), Catharanthus (periwinkle), etc. Usually found in pairs, e.g., Michelia, vinca etc.

Siliqua: It is a long, narrow fruit developing from bicarpellary, syncarpous ovary with parietal placentation. The ovary is one chambered in the beginning but later on becomes two chambered due to the formation of a false partition wall called replum. The seeds are attached on both sides of the replum. At maturity the fruit dehisces along both the sutures from base upward e.g., Brassica (mustard), etc.

Silicula: A short and broad siliqua with relatively few seeds is known as silicula e.g., Capsella bursa-pastoris (shepherd's purse), Iberis amara (candytuft), etc.

Capsule: It is one or more chambered fruit developing from a polycarpellary syncarpous, multilocular and superior ovary. Depending upon the mode of dehiscence, it is of several kinds :

Porocidal capsule : It dehisces by means of pores, e.g., Papaver, Luffa, etc.

Dentidical capsule : It dehisces by apical teeth, e.g., Dianthus, etc.

Pyxidium or Pyxis : It dehisces transversely removing the lid and exposing the box of seeds, e.g., Portulaca, Celosia (cock’s comb), etc.

Valvular capsule : It dehisces by longitudinal slits. Depending upon the manner of dehiscence, it is subdivided into three categories :

Locudicidal capsule : Here the slits appear in the locule along the dorsal suture and the seeds remain attached to the septae, e.g., Malvaceae, Acanthaceae.

Septicidal capsule : In this type the slits appear in the region of septae where the seeds are also attached, e.g., Linum.

Septifragal capsule : In this type the slits in the fruit may appear either in the region of locule or in septae but the seeds are attached to the central column, e.g., Datura.

Types of indehiscent or achenial fruits

Caryopsis: It is a small one seeded fruit developing from a monocarpellary, unilocular and superior ovary. In caryopsis the seed coat is fused with the pericarp to form husk. It is the characteristic fruit of Poaceae (Gramineae); e.g., Triticum aestivum, (wheat) Oryza sativa (rice), Zea mays (maize) etc. Such fruits are called grains.

Achene: It is similar to caryopsis but seed coat is not fused with pericarp, e.g., Ranunculus, Mirabilis (4'O clock plant), etc. Mostly achenes develop in an aggregate.

Cypsela: It is one seeded fruit developing from a bicarpellary, syncarpous, unilocular and inferior ovary. Here the pericarp and the seed coat are separate. Cypsela is a characteristic fruit of the family Asteraceae (Compositae), e.g., Helianthus annuus (sunflower), Tagetes (mariglod), Dahlia etc.

Nut: It is a one seeded fruit developing from a bi-or multicarpellary, syncarpous, unilocular and superior ovary. Nut is characterised by a very tough and stony pericarp; e.g., Anacardium occidentale (cashewnut), Litchi sinensis (litchi), etc. In litchi, the epicarp and mesocarp (layers of the pericarp) together become leathery and the endocarp is membranous. The edible part is fleshy aril whereas in other nuts it is seed.

Caryopsis of Zea Nut of Anacardium Nut of Semicarpous Cypsela of Compositae

Types of schizocarpic or splitting fruits

Lomentum: It is modified legume in which pericarp gets constricted in between seeds. On ripening it gets broken into as many mericarps as there are seeds, e.g., Arachis hypogea (ground nut), Tamarindus (tamarind), Mimosa pudica (sensitive plant), etc.

Cremocarp: It is a dry schizocarpic two seeded fruit developing from a bicarpellary, inferior ovary. At maturity it splits into two one-seeded mericarps. Each mericarp is borne on an elongated axis called carpophore, e.g., Coriandrum (coriander), Foeniculum vulgare, (fennel, saunf) etc.

Regma: It is a dry schizocarpic fruit developing from a tricarpellary, syncarpous, trilocular and superior ovary. At maturity the regma splits into three one seeded cocci e.g., Ricinus communis (castor), Jatropha, etc.

Carcerulus: It is a dry fruit which develops from a bi-or multicarpellary, syncarpous, superior ovary. At maturity it splits into four mericarps, e.g., Ocimum, Salvia, etc.

Samara: It is one or two seeded winged fruit developing from a bi-or tricarpellary superior ovary. The wings are the outgrowths of the pericarp, e.g., Holoptelea. In sal (Shorea robusta) fruit is one seeded and winged like samara but the wings are formed by the persistent calyx. Such fruits which are not the samara but look like it are called samaroid. Hopea, Dipterocarpous, etc. are some other common examples of samaroid fruits.

Cremocarp of Carcerulus of Lomentum of Double samara umbelliferae Geranium Acacia of Acer

FLESHY FRUITS

Fruits in which the entire pericarp or a part of it and/or accessory structures associated with it become fleshy and juicy at maturity.

Types of fleshy fruits

Drupe (stone fruits) : It is one or more seeded fleshy fruit developing from a mono or multicarpellary, syncarpous and superior ovary. The pericarp of drupe consists of a thin epicarp (forms the skin), a fleshy mesocarp (forms the edible part) and hard and stony endocarp. The name stone fruit is given to them due to stony endocarp. It is a true fruit because it develops from a superior ovary and thus has no accessory parts. Prunus amygdalis (almond), Cocos nucifera (coconut), Prunus persica (peach), Mangifera indica (mango), Trapa bispinosa (water chestnut) etc.In coconut, the mesocarp is fibrous (not fleshy as in other drupes) and the edible part is the endosperm of seed.

Berry: It is one or many seeded fleshy fruit developing usually from a multicarpellery, syncarpous and superior or inferior ovary with axile or parietal placentation. In berries the seeds are attached to the placenta in the begining but at maturity they are found loose in the pulp. The pericarp of berries is differentiated into epicarp, mesocarp and endocarp (like drupes) but here the endocarp is not stony as in drupes. The endocarp becomes thin, mucilaginous and gets broken into pieces, each piece surrounding a seed, e.g.. Lycopersicum esculentum (tomato) Vitis vinifera (grapes), Musa paradisiaca (banana). Carica papaya (papaya), Phoenix dactylifera (date plant), Capsicum annum (chilli), Areca catechu (betel or arecanut), Psidium guayava, etc.

Pome : It is a fleshy fruit surrounded by the thalamus. It develops from bi or multicarpellary, syncarpous, inferior ovary. In pome the edible part is thalamus where as the true fruit remains embedded,. e.g., Pyrus malus (apple), Pyrus communis (pear) etc.

Pepo : Like berry, pepo is also a many seeded fleshy fruit but it develops from a tricarpellary, syncarpous, unilocular, inferior ovary with parietal placentation. Although the seeds in pepo are embedded in the pulp but unlike berry they remain attached to the placenta. It is a characteristic fruit of the family Cucurbitaceae, e.g., Lagenaria siceraria (bottle gourd), Citrullus lanatus (water melon), Cucumis sativus (cucumber) etc.

Hesperidium: It is many chambered fleshy fruit developing from a multicarpellary, syncarpous, multilocular, superior ovary bearing seeds on axile placentation. The leathery epicarp of hesperidium has many glands of aromatic oil. The mesocarp, represented by white fibres is fused to the epicarp. The epicarp and mesocarp together form the rind. The endocarp is thin and papery. It projects inwards and forms many compartments. The inner wall of endocarp gives out many juicy succulent hairs which form the edible part of the fruit. Hesperidum is a characteristic fruit of the family Rutaceae, e.g., Citrus aurantifolia (lemon), Citrus reticulata (oranges) etc.

Balausta: This is many chambered, many seeded fruit developing from a multicarpellary, syncarpous but inferior ovary. The pericarp of balausta is leathery or tough. The carpels are arranged in two rows. Calyx is persistent. The seeds have succulent seed coat (testa) which forms the edible part, e.g., Punica granatum (Pomegranate).NCERT consist of good explanations of this concept and for questions of NCERT refere NCERT solutions for class 12 biology.

Amphisarca: It is many seeded fleshy fruit with a stony pericarp. It develops from a multicarpellary, syncarpous, superior ovary. The edible part of the fruit is the inner fleshy layer of pericarp and the placentae e.g., Aegle marmelos, (wood apple), Feronia limonia, etc.