Fruits: Simple, Aggregate and Composite Fruits

The following points highlight the three major types of fruits. The types are: 1. Simple Fruits 2. Aggregate Fruits 3. Composite Fruits.

Fruit: Type # 1. Simple Fruits:

When the ovary of a flower with or without other accessory floral parts converts into a single fruit, the fruit is said to be a simple fruit. It may be dry or fleshy.

The dry fruits may further be classified into:

(i) Dehiscent,

(ii) Indehiscent and

(iii) Schizocarpic fruits.

(i) Dry Dehiscent Fruits:

(a) Legume or pod:

This type of simple dry fruit is monocarpellary, developing from a superior, one chambered ovary. It dehisces by both the sutures. Typical examples are found in Leguminosae family, e.g., pea, bean, pulses, gram and many others.

(b) Follicle:

This type of simple dry fruit is monocarpellary, developing from a superior, one-chambered ovary like the legume fruit, but it dehisces by one suture only as in Calotropis (Ak), Asclepias, Vinca rosea (Sadabahar), Michelia, etc.

(c) Siliqua:

This is a long, narrow, many seeded fruit which develops from a superior bicarpellary ovary with two parietal placentae. It dehisces from below upwards by both the sutures Here the ovary is one-chambered at first, but later on it becomes two-chambered because of the development of a flase septum, the replum, which extends from one placenta to another.

This type of fruit is commonly found in Brassicaceae (Cruciferae), e.g., mustard, radish, Eruca, etc.

(d) Silicula:

When a siliqua fruit becomes much shorter and flattened and as broad as it is long with a few seeds, it is called silicula, e.g., Capsella and candytuft (Iberis amam).

(e) Capsule:

This is a many-seeded, uni-or multilocular fruit which develops from a superior bi-or polycarpellary ovary. It dehisces in many ways. The dehiscent fruits which develop from a syncarpous ovary are commonly called capsule fruits.

A capsule may dehisce by pores as in poppy or transversely in cock’s comb; or loculicidally, as in cotton and Bhindi septicidally, as in linseed and septifragally as in Datura. In Datura the dehiscence lines are irregular and expose the central column bearing seeds.

(ii) Dry Indehiscent or Achenial Fruits:

These fruits are dry and one-seeded. Here the pericarp does not split or break open to allow the seed to escape. They develop from monocarpellary to polycarpellary syncarpous pistil with one chamber and one ovule.

The main kinds of such fruits are as follows:

(a) Caryopsis:

This is a very small, dry, one-chambered and one-seeded fruit which develops from a superior monocarpellary ovary. Here the pericarp remains fused with the seed coat. The well known examples are found in Poaceae (Gramineae) family, e.g., maize, wheat, barley, millets, etc.

(b) Achene:

An achene is a small, dry indehiscent fruit. It develops from a superior monocarpellary, one-chambered and single ovuled ovary. The pericarp is thin and leathery and encloses a single seed. The pericarp remains free from the testa or seed coat.

The achenes are commonly developed from an apocarpous pistil, and therefore a single flower produces as many achenes as many free carpels are there, e.g., Clematis, Naravelia, Ranunculus etc.

(c) Cypsela:

This is a dry, one-chambered and one-seeded fruit. It develops from an inferior bicarpellary ovary. The pericarp and the seed coat remain free from each other. The examples are commonly found in Asteraceae (Compositae family, e.g., sunflower, Cosmos, Tagetes, Ageratum Sonchus, etc.

(d) Nut:

This is a dry, one-chambered and one-seeded fruit with hard and woody epicarp. It develops from a superior bi-or polycarpellary ovary, e.g., chestnut, oak, walnut, etc.

In Litchi the nut develops from a tricarpellary, syncarpous, superior and trilocular ovary with more than one ovules. On the maturity of the fruit only one ovule develops into a mature seed The juicy aril which is an outgrowth of the testa from micropylar end surrounds the whole seed’ The fleshy and juicy aril is edible.

The pericarp is hard and leathery and bears numerous echmulate tubercles on it. It becomes brownish red at maturity.

In Juglans regia (English walnut) the fruit is a nut which develops from bicarpellary syncarpous, inferior and one-chambered ovary with one basal ovule. Here the fruit remains surrounded by an exocarp of fused involucre and perianth surrounding the ovary. It makes the husk of the fruit and is removed by burning it before marketing the fruits.

The thalamus and pencarp are hard and woody. The seed is large with convoluted cotyledons, which make the edible part of the nut. The stony pericarp is produced into ingrowths.

In cashewnut (Anacardium occidentale) the fruit (nut) develops from a monocarpellary superior, single-chambered, single-ovuled ovary. The thalamus becomes fleshy and edible. The kernel of true nut is also edible.

In Chenopodium the nut remains surrounded by persistent perianth and is known as utricle.

The fruit (nut) develops from a bicarpellary, syncarpous superior and unilocular ovary with single basal ovule.

In oak (Quercus spp.) the nut develops from a tri-carpellary syncarpous and in­ferior ovary. Here only one ovule develops into a seed. The pericarp is smooth, brown and hard. It rem­ains enveloped at its base by a cupular structure, the cupule. The cupule is formed by the fusion of hard and persistent bracts.

In chestnut, the cupule develops small spine-like outgrowths. Here the cupule surrounds three nuts.

(e) Samara:

This fruit is dry, indehiscent, one-or two seeded and develops from a superior, bi-or tricarpellary ovary, with flattened wing-like outgrowths, e.g., Hiptage, Dipterocarpus, Acer, etc. Here the wings always develop from the pericarp, and the fruit breaks into its component parts, each enclosing a seed.

The fruit of Shorea is also winged, but here the wings are dry and persistent sepals. Such winged fruits are called samaroid fruits.

(iii) Splitting or Schizocarpic Fruits:

They are dry, many seeded, indehiscent fruits. The fruits generally break into many or few one-seeded portions, the mericarps. The mericarps are indehiscent. In certain schizocarpic fruits, e.g., castor the one seeded parts of the fruit are dehiscent, and are called cocci.

They are of following types.

(a) Lomentum:

It is characteristic of Mimosaceae family, e.g.. Acacia, Mimosa, etc., the fruit is derived from a monocarpellary superior, unilocular ovary with marginal placentation. Here the legume is constricted or partitioned, into a number of one-seeded mericarps.

(b) Cremocarps:

This type of fruit is dry indehiscent and two-chambered. It develops from an inferior, bicarpellary ovary. On maturity the fruit splits apart into two indehiscent, one seeded portions, the mericarps. The mericarps remain attached to the prolonged end of the axis, known as carpophore. This type of fruit is characteristic of Apiaceae (Umbelliferae) family, e.g., coriander, fennel, carrot, cumin, etc.

(c) Carcerulus:

This type of fruit is derived from a syncarpous and superior ovary with many chambers and axile placentation. Each loculus may possess one or two ovules. The mature fruit splits into many single seeded and indehiscent mericarps, e.g., Althaea rosea (hollyhock), Abutilon indicum (Kanghi), Salvia, Ocimum, etc.

(d) Regma:

This type of fruit is characteristic of castor plant (Ricinus communis). It develops from tricarpellary, syncarpous, superior, trilocular ovary with axile placentation. The fruit wall bears spine like tubercles. The locules are separated from each other on maturity by an explosive mechanism. These dehiscent locules are known as cocci, and remain attached to a central column, the carpophore.

The regma fruit is also found in Geranium. In this case it is derived from a pentacaipellary, syncarpous and superior ovary. The carpels remain fused around the base of a central axis the carpophore. On maturity, the fruit breaks into free single seeded cocci.

(e) Double samara:

It is derived from a superior, bi-or-tricarpellary, syncarpous ovary with a single ovule in each loculus. Two or three wings are produced from the pericarp. The mature fruit breaks into two or three, indehiscent, single seeded mericarps. Examples are Acer, Dodonaea.

Fleshy Fruits:

In these fruits the pericarp becomes fleshy and edible. Such fruits may be one-or many chambered, one- or many-seeded or inferior, with axile or parietal placentation. Commonly they are indehiscent fruits, and their seeds may be liberated only on the decay of the pulp.

The pericarp of fleshy fruits is generally distinguis­hed into three parts, (a) epicarp, (b) mesocarp and (c) endocarp. Epicarp is the outermost layer of the pericarp.

It is the protective layer and may be thin or smooth or thin and papery. In Aegle marmelos it becomes hard and stony. Just beneath the epicarp, the mesocarp is found. In some {e.g., mango) it is fleshy, juicy and edible, whereas in others it is fibrous (e.g., coconut). In orange and banana it is thread like.

The endocarp is the inner most layer of the pericarp. It is hard and stony in mango; fleshy and edible in banana and tomato. In orange the endocarp is thin and papery and bears juicy hair on its inner surface. Here the juicy hairs are edible.

1. Drupe:

This is a fleshy, one-or more chambered and one-or more seeded fruit. It develops from a monocarpellary or syncarpous pistil. The pericarp of the fruit remains differentiated into thin epicarp, fleshy mesocarp and stony endocarp. Because of the presence of stony endocarp the fruit is also known as stone fruit, e.g., mango, peach, plum, coconut, almond, etc.

2. Berry or Bacca:

This is a superior or inferior, indehiscent, many seeded and fleshy fruit. It develops from a single carpel or from a syncarpous pistil with axile or parietal placentation, e.g., tomato, grapes, brinjal, guava, papaw, etc. In this type of fruit the seeds at first remain attached to the placentae, but later on they are detached from the placentae and lie free in the pulp.

The date-palip and Artabotrys are the examples of one-seeded berry. The pericarp of berry is also differentiated into epicarp, mesocarp and endocarp but like drupe the endocarp is not stony.

3. Pepo:

This type of fruit is characteristic of Cucurbitaceae family, e.g., gourd, cucumber, melon, watermelon, squash, etc., the fruit is fleshy or pulpy and many seeded. It develops from an inferior, syncarpous pistil with parietal placentation. Here the seeds remain embedded in the pulp and attached to the placentae.

4. Pome:

This type of fruit is found in Rosaceae family, e.g., apple, pear, etc., the fruit develops from pentacarpellary, syncarpous and inferior ovary with many seeds. The fruits remain surrounded by fleshy thalamus. The fleshy thalamus makes the edible part, whereas the actual fruit lies within it.

The outer portion of the pericarp (i.e., epicarp and mesocarp) is fleshy and fused with the thick edible portion (thalamus). The inner layer of pericarp (i.e., endocarp) is cartilaginous and forms the core surrounding the seeds. Each part of the core represents one of the five carpels. The remains of the perianth may be seen at the top of the fruit.

5. Hesperidium:

This type of berry is derived from a polycarpellary, syncarpous superior, multilocular ovary with axile placentation and many ovules. Here the epicarp is thick and leathery and contains oil cavities. Next to epicarp there is white thread-like fibrous layer of mesocarp.

The endocarp projects inwards forming distinct chambers. The inner walls of the endocarp give rise to numerous juicy outgrowths which makes the edible part of the fruit, e.g., orange, lemon, etc.

Fruit: Type # 2. Aggregate Fruits:

Such fruit develops from a single flower having an apocarpous pistil. In such case the carpels are free, and each of them develops into a simple fruitlet. A collection or a group of simple fruitlets makes an aggregate fruit. As many fruitlets are developed in a group as carpels are there in a flower.

An aggregate of simple fruitlets on a single flower is termed as etaerio-such as an etaerio of achenes, an etaerio of follicles, an etaerio of drupes, an etaerio of berries, etc.

(i) An Etaerio of Achenes:

This type of fruit develops from polycarpellary apocarpous gynoecium. For example, in Clematis and Naravelia the achenes are provided with feathery and persistent styles, in Rosa the achenes remain enclosed in a hollow, receptacular thalamus, in Fragaria the achenes are found on the fleshy thalamus and in Nelumbo the fruitlets occur on a flat, top-shaped spongy thalamus.

(ii) An Etaerio of Follicles:

In this case fruit develops from a bicarpellary apocarpous (e.g., in Calotropis) or tricarpellary (e.g., in Aconitum) or polycarpellary apocarpous (e.g., in Michelia) gynoecium. In Asclepias and Calotropis each etaerio consists of a pair of follicles. In Aconitum an aggregate of three follicles is produced on the top of the thalamus, whereas in Michelia numerous follicles are developed on an elongated thalamus.

(iii) An Etaerio of Drupes:

The characteristic example of this type is found in Rubus (raspberry). It develops from superior, polycarpellary and apocarpous gynoecium. The carpels are borne on a conical thalamus. Here a number of small drupelets develop from separate carpels of a flower and they are grouped together on a fleshy thalamus.

(iv) An Etaerio of Berries:

In this type of fruit each carpel of an apocarpous pistil develops into a berry. During development the margins of the carpels may be fused (e.g., in Annona squamosa) or they may remain separate from each other (e.g., in Artabotrys odoratissimus). In Annona squamosa the mesocarp of berries is edible.

Fruit: Type # 3. Composite Fruits:

A composite or multiple fruit develops from the entire inflorescence. Here the flowers as well as the peduncles on which they are borne take part in the development of the fruit. Such a fruit is also known as infructescence.

There are two main types of such fruits:

(i) Sorosis:

This type of multiple fruit develops from a spike or spadix. Here the flowers fuse together by their perianth lobes and simultaneously the axis bearing them becomes fleshy and juicy, and as a result the whole inflorescence forms a compact mass, e.g., pine apple, jack fruit, etc. In Morus (mulberry), the perianth lobes become thick and juicy and are edible.

Here the ovules do not mature into seeds and therefore, the carpels develop into small nutlets that are seedless.

(ii) Syconus:

This type of composite fruit develops from a hollow, pear-shaped, fleshy receptacle which encloses numerous minute male and female flowers. The receptacle develops further and converts into the so-called edible fleshy fruit. It really encloses a number of true fruits or achenes which develop from the female flowers of the hypanthodium inflorescence, e.g., fig, banyan and many species of Ficus.