In this tutorial, we have discussed different types of fruits in biology and their significance.

WHAT ARE FRUITS

— True fruit or eucarp is a ripened ovary which develops under the influence of ripening ovules and is meant for protecting them. It consists of a pericarp formed from the wall of the ovary and seeds formed from ovules.

The pericarp may be dry or fleshy, when fleshy it consists of the outer (epicarp), middle (mesocarp), and inner (endocarp) walls.

A fruit in which other floral parts (e.g., thalamus, base of sepals, petals, etc.) fuse with the pericarp is called false fruit or accessory fruit or pseudocarp (e.g., Apple, Mulberry, Strawberry).

The fruits, which develop only from the ovary, are called true fruits.

Pomology is the study of fruits. 

A fruit that is formed without fertilization and thus without seed is called seedless fruit or parthenocarpic fruit, e.g., banana.

Broadly, fruits are divided into three groups-simple (formed from a flower having a single pistil), aggregate (from a flower having polycarpellary apocarpous gynaecium),- and composite (from a whole inflorescence).

Fruits are of three main types: Simple fruits, aggregate fruits, and multiple fruits.

I. Simple Fruits

Simple fruits develop from the monocarpellary ovary or multicarpellary syncarpous ovary of a flower.

Simple fruits are of two types: Simple dry fruits and Simple succulent (fleshy) fruits.

A. Simple Dry Fruits

In dry fruits, pericarp is dry. It is neither fleshy nor differentiated into three layers as in succulent fruits. Simple dry fruits are further divided into three types: (a) Achenial or Indehiscent (b) Capsular or Dehiscent and (c) Schizocarpic or splitting.

1. Achenial / Indehiscent Fruits

These are single-seeded, dry simple fruits that do not dehisce or rupture after ripening and remain inside the pericarp. These are of following five types:

(i) Achene

It is a small dry, one chambered, one seeded fruit developing from superior or inferior monocarpellary unilocular ovary. The thin dry pericarp is free from the seed coat except at one point, e.g., Mirabilis jalapa (Four o’clock), Boerhaavia, etc. Sometimes achenes occur in a group from apocarpous ovary where carpels are many e.g., Lotus (Nelumbium). These are common in aggregate fruits, e.g., Ranunculus, Clematis, etc.

(ii) Caryopsis

It is very small, dry and one seeded fruit that develops from monocarpellary, unilocular, superior ovary. The thin dry pericarp is completely fused with seed coat or testa. It is characteristic of family graminea, e.g., rice (Oryza sativa), wheat (Triticum aestivum), maize, oat, etc.

(iii) Cypsela

It is dry, one seeded fruit that develops from an inferior, bicarpellary, unilocular ovary. Here the pericarp is free from the seed coat but the thalamus is fused with that forming a part of the fruit i.e., in Compositae, e.g., sunflower, marigold, cosmos, etc. Pappus or persistent calyx is present in fruits.

Some cypselas develop hairy pappus for seed dispersal by wind, e.g., Sunflower, Marigold, Sonchus, Dandelion (Taraxacum), etc.

(iv) Nut

It is dry, one seeded fruit that develops from a bicarpellary or multicarpellary, inferior ovary. Only a single ovule reaches maturity to form a single seed. The single-seeded, dry indehiscent fruit is hard, stony, woody, or leathery, e.g., Cashewnut (Anacardium occidentale), Betel nut (Areca catechu), Water chestnut (Trapa), Oak, Litchi, Walnut (Juglans), etc.

(v) Samara

It is dry, one or two seeded fruit, develops from a superior mono or bicarpellary ovary. The pericarp is free from testa and produces a wing like outgrowth that helps in wind dispersal of seeds. Examples: Holoptelia integrifolia (Indian Elm), Ulmus (Elm). In Shorea (Sal) persistent sepals form wings, Such fruits are called samaroids.

2. Capsular / Dehiscent Fruits

These are many-seeded, dry, simple, and dehiscent fruits. Their pericarp ruptures after ripening and seeds are dispersed. These are of five types:

(i) Legume or Pod

It develops from monocarpellary, unilocular, superior ovary with marginal placentation. Mature fruit dehisces by both dorsal and ventral sutures. It is a characteristic of family leguminosae, e.g., Pea, Gram, Bean, Abrus, etc.

(ii) Follicle

It is similar to legume but dehisces by one suture only, generally ventral. Examples: Larkspur, Calotropis, Milkweed, etc.

(iii) Siliqua

This fruit develops from bicarpellary, syncarpous, superior ovary with parietal placentation, Ovary is unilocular in the beginning but becomes bilocular due to the development of false septum called replum. Dehiscence starts from the lower part (base) and proceeds upwards (apex) by both the sutures. Seeds are dispersed by wind. It is a characteristic of family cruciferae, e.g., Mustard (Brassica).

(iv) Silicula

It is a few-seeded, flattened, and shortened siliqua. Examples: Capsella (Shepherd’s Purse), Iberis (Candytuft), etc.

(v) Capsule

It develops from multicarpellary, syncarpous, superior, or inferior ovary. It is multilocular and many seeded. The important types of capsules are as follows:

(a) Loculicidal Capsule

The fruit dehisces along the dorsal sutures of the ovary by longitudinal slits into loculi, e.g., Cotton (Gossypium herbarium), Lady’s finger (Okra; Abelmoschus esculentus), etc.

(b) Septifragal Capsule

Lines of dehiscence along irregular lines, but the seeds remain attached to the placenta as in thorn apple (Datura stramonium).

(c) Porocidal Capsule

The capsule dehisces by pores as in Poppy, Luffa, and Dog Flower. In Poppy, the fruit has a persistent stigmatic disc.

(d) Pyxidium or Pyxis

A transverse circular suture separates the lid from the fruit to expose the seeds, e.g., Portulaca, Celosia (cock’s comb), etc.

(e) Denticulate or Denticidal Capsule

The mature capsule breaks apically in teeth-like projections, e.g., Dianthus (Pink). 

(f) Septicidal Capsule

Longitudinal slits appear along the middle of the septa and the placentae along the line of union, e.g., Viola (Pansy), Linum (Linseed), etc.

3. Schizocarpic Fruits

These are dry, many-seeded, and simple fruits. On ripening these break up into single seeded mericarps when indehiscent and cocci if dehiscent. These are intermediate between dehiscent and indehiscent fruits and are of the following five types:

(i) Cremocarp

It s a dry fruit, develops from bicarpellary, syncarpous, bilocular ovary. The fruit when mature breaks into single seeded mericarps, which remain attached to the top of the central axis called carpophore, by means of stylopodium as in Coriander (Coriandrum sativum), Fennel, Cumin, Carrot (Daucas carota) etc.

It is characteristic fruit of umbelliferae.

(ii) Carcerulus

It develops from a superior, bi or multicarpellary ovary. Many single-seeded mericarps are formed by splitting or formation of false septum.

Characteristic of Althaea and Abutilon (Malvaceae), Ocimum (Labiatae), and Garden nasturtium (Tropaeolum majus; Tropaeolaceae).

(iii) Double or Compound Samara

It develops from bicarpallary, syncarpous, superior ovary. Pericarp develops in two wings. On maturation it divides into two one-seeded mericarps., e.g., Hiptage, Acer, etc.

(iv) Lomentum

It is a dry many seeded fruit which develops from monocarpellary, superior, unilocular ovary with marginal plancentation. This fruit has a beaded appearance due to constrictions between the seeds. It may be indehiscent or break up into single-seeded parts. These parts may be indehiscent (mericarps) or dehiscent (cocci), e.g.,

(v) Regma

It is a dry fruit which develops from tri pentacarpellary, syncarpous, superior ovary. The fruit breaks up into single-seeded cocci. The cocci remain attached to the carpophore, the central axis, for some time. Regma of Castor is tubercled. It splits up into three cocci along with hygroscopic styles. The hygroscopic styles shake the seeds out of cocci.

B. Simple Succulent Fruits

These are simple fruits with a fleshy pericarp. Pericarp is differentiated into outer epicarp, middle mesocarp, and inner endocarp. The mesocarp is fleshy or fibrous. The succulent fruits are indehiscent. Their seeds get separated after the decay of fleshy mesocarp. The main groups of succulent fruits are:

1. Berry / Baccate Fruits

These fruits develop from mono or multicarpellary superior or inferior syncarpous ovary with axile or parietal placentation. Epicarp makes the rind (outermost skin) of fruit and mesocarp is fleshy.

The endocarp is either pulpy (Date, Brinjal, Banana, and Guava) or juicy (Grape, Tomato). The fruit is single-seeded in Date but many-seeded in others. The seeds at first remain attached to the placenta but later on, become detached and embedded in the pulp.

In superior or true berries, derived from superior ovaries, all the three parts of the pericarp are edible. In false or inferior berries derived from inferior ovaries, the epicarp is fused with the thalamus to form the skin, also called the exocarp. The remains of the calyx appear as a crown at the tip of the fruit.

Examples: Grapes, Date, Tomato, Banana, and Guava.

Special Berries are of five types:

(i) Balausta

This fruit develops from multilocular, syncarpous, inferior ovary. The seeds possess juicy testa. Whole fruit is covered by a hard rind made of exocarp and part of mesocarp. Endocarp is papery and covers the individual groups of seeds.

Example: Pomegranate (Punica granatum).

(ii) Amphisarca

It develops from multicarpellary, syncarpous, multichambered, superior ovary. Epicarp is hard and woody. Mesocarp, endocarp, and swollen placenta are edible.

Example: Aegle (Bael).

(iii) Pepo

It develops from the inferior ovary with parietal placentation. It is a false berry in which rind or exocarp does not separate from mesocarp. Similarly, the seeds are found in the pulp attached with placenta.

Examples: It is characteristic fruit of the family Cucurbitaceae. Bottle gourd, Cucumber, Watermelon, and Muskmelon.

(iv) Hesperidium

This fruit develops from the syncarpous, superior ovary with axile placentation. Epicarp has many oil glands. Mesocarp is in the form of white, fibrous part fused with epicarp. Endocarp is membranous and forms several chambers. Unicellular juicy hair are present on the inner side of the endocarp. These are edible parts. Seeds lie embedded in juicy hair.

Examples: Citrus (Lemon, Orange, etc.), Chakotra.

(v) Fibrous Berry

It is a single-seeded special berry which is formed from superior ovary. Pericarp consists of a thin epicarp, a thick fibrous mesocarp and a fleshy edible endocarp. The fruit becomes hard when dry. 

Examples: Betel Nut (Supari: Areca catechu), coconut (Cocos nucifera).

(vi) Drupe

These are also called stone fruits because endocarp of these fruits is hard and stony. The stony endocarp encloses one seed, rarely more (two in Zizyphus) and three in (Borassus). Drupe develops from mono or multicarpellary, superior or inferior ovary. In superior drupes, epicarp forms the outer skin. It is edible in Peach, Plum, Zizyphus, Cherry, etc., but is inedible in Mango, Trapa, Walnut, Coconut, etc. Mesocarp may be pulpy and edible (in Zizyphus, Mango, Plum, Cherry, etc) or fibrous (in coconut; Cococs nucifera)

Examples: Peach, Plum, Zizyphus, Cherry, Mango, Trapa, Walnut, Coconut, etc.

(vii) Pome

It is a false fruit that develops from the fleshy thalamus of multicarpellary, syncarpous, inferior ovary. Wall of the ovary, is papery, and seeds develop inside the locules. Fleshy swollen thalamus is edible, e.g., Apple (Pyrus malus), Pear (Pyrus communis), Lokat (Eriobotrya japonica). 

II. Aggregate Fruits

These fruits are group of fruitlets which develop from multicarpellary, apocarpous ovary. These fruits make an aggregate of fruitlets. Such type of aggregate fruits develop from a single flower known as etaerio. These are of the following types:

1. Etaerio of Follicles

In such fruits, each carpel develops into a fruitlet which is known as follicle. In Calotropis and Catharanthus, etaerio develops from two follicles, and in Michelia, it develops from many follicles.

2. Etaerio of Berries

It is an aggregate fruit of small berries. Many berries develop on all the sides of fleshy thalamus. Apical parts of berries fuse with each other to make a common rind, e.g., Custard apple.

3. Etaerio of Drupes

In Raspberry and Blackberry, many drupes aggregate on the same axis to form etaerio of drupes.

4. Etaerio of Achenes

Each fruitlet is an achene thatdevelops from multicarpellary, unilocular, apocarpous ovary. The achenes are aggregated on a single axis to produce etaerio of achenes. Examples: Rose, Strawberry, Nelumbium, Clematis, Narvelia, Ranunculus (Butter cup), Lotus, etc.

In Rose, achenes are present on the cup-like thalamus. In Lotus, thalamus becomes spongy and achenes are embedded in it. In Strawberry, thalamus becomes fleshy and edible.

III. Multiple Fruits or Composite Fruits

Multiple fruits develop from the complete inflorescence. These are of the following types:

1. Sorosis

It is multiple and fleshy fruit that develops from a spike in pineapple (Ananas), a female catkin in mulberry, and a spadix in jackfruit (Artocarpus).

(a) Mulberry (Morus) develops from female catkin. Ovaries of individual flowers develop minute sedless fruitlets. Their perianth becomes fleshy and juicy and the whole fruit is edible.

(b) Pineapple (Ananas camosus) develops from the spike of sterile flowers with persistent bracts. When the peduncle enlarges and becomes fleshy, part of the sterile flowers gets embedded. Rhomboidal areas found on the outside of the fruit represent the position of individual flowers.

(c) In Jack fruit (Kathal) pistillate flowers develop very close to each other around the rachis. Bracts, perianth, and seeds become succulent and are edible. Stigmas fuse with each other to make rough and spiny rind.

2. Syconus

— It is also a multiple fruit that develops from hypanthodium inflorescence.

— Here, the peduncle (receptacle) becomes fleshy and many achenes develop from the pistillate flowers. Fleshy receptacle of these fruits is edible, e.g., Fig.

I. Economic Importance of Fruits

1. Because of their taste and flavour, fruits have been eaten by human beings since ancient times. Some of the edible fruits are either dry or can be dried, e.g., Cashewnut. Such fruits can be stored for a long. 

2. Cereals, the one-seeded dry fruits, constitute the staple food of man.

3. A large number of fruits like Cucumber, Lady’s finger, Tomato, Pumpkin, etc., are used as vegetables.

4. Fruits are a source of vitamins, minerals, organic acids, pectin, sugar, etc.

5. A few fruits are used in medicines. Unripe fruits of Papaver somniferum provide latex which is used in making opium.

6. Fruits are an important item of food for fruit-eating (frugivorous) birds.

II. Biological Importance of Fruits

1. The fruit forms a protective covering against desiccation around the seeds during their growth to maturity.

2. The fruit provides protection to the enclosed seeds against unfavourable physical environment.

3. The young fruits are green and remain hidden in the foliage.

4. The young fruits have a hardcore.

5. The immature fruits are bitter due to the presence astringents, tannins bitter alkaloids, and sour acids. They, therefore, keep the animals away.

6. In the mature state, the fruits become sweet, coloured and flavoured to attract animals and human beings for plucking and eating. During the process, animals and human beings also disperse their seeds.