Here is your essay on fruits and seeds

The post-fertilization changes in angiosperm results in the formation of fruits and seeds. It is found that out of two male gametes in the pollen tube, one fuses with the egg cell forming embryo, and the latter undergoes a series of changes to form the seeds.

Other male gamete fuses with the secondary nucleus of the embryo sac forming a triploid endosperm. In the meantime, other parts of the ovary get trans- formed into the fruit. The fruit provides necessary protection to the seed and helps in its dispersal from the mother plant to outside, where the seed can germinate to give rise to new plant of its own kind.

FRUITS:

Fertilization leads to the development of embryo inside the embryo sac of the ovule. Along with series of changes in the embryo, the ovule is converted into the seed while the wall of the ovary and other parts of the flower connected to it change into a fruit.

Thus, fruit is defined as ripened ovary. Its biological need is to protect the seeds by forming a case or vessel around it. It also assists in the dispersal of seeds. Sometimes the fruits may be formed without fertilization. This condition is called parthenocarpy and the fruit is known as parthenocarpic fruit.

PARTS OF A FRUIT:

A fruit consists of seeds and its wall called, per carp. The per carp is distinguished into three parts such as outer epicarp (the skin of ovary), the middle mesocarp which may be pulpy (e.g., mango, peach, palms, etc.) and the inner endocarp which is often very thin and membranous (e.g., orange) or very hard and stony (e.g., palms, mango).

In many cases per carp is not differentiated into three parts. When the fruit is developed only from the single ovary of a flower it is called true fruit. But sometimes the thalamus, receptacle or calyx may also grow and form a part of fruit.

In such cases, it is known as false fruit or spurious fruit (Pseudo carp). Some the spurious fruits, developed involving different parts of the flower, are described.

DIFFERENT TYPES OF DEHISCENCE:

Fruits, when ripe, may become fleshy and pulpy or dry up becoming papery or stony. The fruits split open at maturity in order to discharge the seeds to outside. Such fruits are dry and are called dehiscent fruits.

The fruits which do not open at maturity are called indehiscent fruits. There are various ways by which dehiscence of fruits take place. According to the mode of opening, the different types of dehiscence marked in the fruit are given in.

TYPES OF FRUITS:

All the fruits (true or spurious) are classified into three main groups- simple, aggregate and multiple or composite.

A. Simple fruits:

A fruit developing from a single ovary (monocarpellary or polycarpellary syncarpous gynoecium) of a flower is known as simple fruit. It may be dry or fleshy. The dry fruit again is divided into dehiscent, indehiscent and schizocarpic (splitting) fruits.

I. Dehiscent or Capsular fruits:

The fruits of this category burst automatically on ripening, discharging the seeds. This may be of following types.

(i) Legume or pod: It is a simple, dry, dehiscent fruit. It develops from a monocarpellary, superior, one chambered ovary. It dehisces by both the sutures from apex to the base, e.g., members of Fabaceae such as Pisum, Cicer; etc.

(ii) Follicle: It resembles legume type of fruits being developed from monocarpellary, unilocular, superior ovary but differs from the legumes as it dehisces along one suture (usually ventral) only, e.g., Calotropis. In Calotropis, it shows a paired follicle developing from bicarpellary ovary.

(iii) Siliqua: The fruit is developed from a bicarpellary, syncarpous, superior ovary which is one chambered but appears two chambered due to the development of a false partition wall known as replum.

The fruit of this type dehisces along both the sutures from the base upwards, the seeds remaining attached to the replum, e.g., fruits of Brassicaceae such as Brassica, Raphanus, etc.

(iv) Silicula : It resembles the siliqua type of fruit but much shorter and flattened, being nearly as broad as its length and contains only a few seeds, e.g., Capsella bursa-pastoris, Iberis amara etc.

(v) Capsule: Lt is a many-seeded, uni-or multi ocular fruit. This kind of fruit develops from a superior (or sometimes in- ferior) bi-or polycarpellary ovary. It dehisces in various ways. It may dehisce by pores (e.g., Papaver) or transversely (e.g., Celosia) or loculicidally (e.g., Abelmoschus esculentus) or septicidally (e.g., linseed) or septifragally (e.g., Datura).

(vi) Pyxis: It is a capsule type of fruit which splits open transversely along a circular line. The upper valve serves as cap, e.g., Celosia, Portulaca.

11. Indchiscent fruit or Achenial fruit:

This type of fruit is simple; dry and indehiscent. Based on its development, it is divided into the following types:

(i) Caryopsis: A small, dry, one seeded fruit, it develops from a superior, monocarpellary ovary. In this case, the pericarp is fused with the seed-coat, e.g., members of Poaceae such as rice, maize, etc.,

(ii) Achene: It is similar to caryopsis but the pericarp is not completely fused. It develops from a superior, monocarpellary ovary with the pericarp free from the seed-coat, e.g., Mirabilis, Potentilla, etc.,

(iii) Cypsela: It is a one seeded fruit developing from bicarpellary, syncarpous, one chambered, epigynous or inferior ovary. In this case, pericarp and seed-coat are separate, e.g., members of Asteraceae, such as Helianthus, annus (sunflower), Tagetes patula (marigold) and Dahlia, etc.

(iv) Samara: It is a simple, dry, indehiscent, one or two seeded fruit, developing from a supe- rior, bor tricarpellary ovary, with flat- tened wing-like outgrowths, e.g., Hiptage, Dioscorea, Acer. Wing-like samara is also found in the fruit of Shorea robusta. But here the wings are dry, per- sistent sepals. Winged fruit of this nature is known as samaroid.

(v) Nut: It is a dry, one-chambered and one- seeded fruit developing from a superior, bi-or polycarpellary ovary. In this case, the per carp is hard and woody, e.g., chestnut, Anacardium occidentale (cashew-nut), Trapa bispinosa (water chestnut), Litchi chinensis, etc.

However, coconuts and palmyra- palms fruits are not nuts because in them endocarp becomes hard and woody. In Areca or betel-nuts and date-palms, the pericarp is soft (fibrous in areca-nuts and pulpy in date-palms). It is the seed, that is stony and not pericarp as described above. So, these fruits do not come under nut.

III. Schizocarpic or Splitting fruits:

This type of fruit breaks up into a number of indehiscent bits called mericarp. So it is in between dehiscent and indehiscent dry fruits since each of the mericarp discharges the seed only on the rotting of the pericarp. There are several types of schizocarpic, dry, simple fruits.

(i) Lomentum: The fruit is legume type, but constricted or partitioned between the seeds into a number of one-seeded parts. It usually breaks up into bits containing one or more seeds, (e.g., Acacia, Mimosa, etc.).

(ii) Cremocarp: It is a dry, two-seeded indehiscent, schizocarpic fruit, developed from the inferior, bicarpellary ovary. When ripe, it splits into two mericarps. These are attached to the carpophore (prolonga- tion of the thalamus), e.g., coriander, cumin, carrot, etc.

(iii) Double samara: It is a type of two or more chambered winged fruit developing from syncarpous ovary. The wings are formed out of the pericarp and the fruit breaks up into two component parts, each enclosing a seed, e.g., maple.

(iv) Regma: It develops from polycarpellary ovary. The fruit breaks up into many components equal to the number of carpels. Each one is called cocci, e.g., castor, Jatropha, Hura and Geranium, etc.

(v) Carcerulus: It is the fruit developed by the superior, bicar:pellary ovary with falsely formed four chambers and having a gynobasic style. The seeds are liberated by the decomposition of the pericarp, e.g., Ocimum, Salvia, Abutilon, Althaea, etc.

(vi) Utricle: The fruit is one seeded developing from a bicarpellary, syncarpous, unilocular, superior ovary. It has thin pericarp which splits open by a lid, e.g., Achyranthes, Amaranthus, etc.

B. Fleshy fruits:

The fruits which become fleshy, remain succulent and juicy, are called fleshy fruits. Normally, they are indehiscent, so that seeds are set free only after the decay of the pulp. This includes the following types:

(i) Drupe (stone fruits): It is a fleshy, one-or more- chambered and one-or more- seeded fruit. Normally, it is one- seeded with a skinny epicarp, a fibrous and juicy mesocarp and stony hard endocarp, e.g., mango, peach, and Indian plum’.

These are called ‘stone fruits’ because of the stony hard endocarp. In case of more-seeded drupe, every seed has got a separate endocarp around, e.g., Borassus flabellifer, It is a true fruit since it develops from monocarpellary or polycarpellary syncarpous and superior ovary.

In coconut, the mesocarp is fibrous (not fleshy as in other drupes) and the edible part is the endosperm of seed. Other examples of drupe are peach (Prunus) and country almond, etc,

(ii) Bacca or berry: It is a one or many seeded pulpy fruit. It develops from a single carpel or more commonly from a syncarpous ovary with axile or parietal placentation. Any fleshy fruit in which there is no hard part excepting the seeds as considered as bacca.

The pericarp is differentiated into epicarp, mesocarp and endocarp or all of these may form a pulp in which the seeds are embedded. In the beginning, the seeds are attached to the placenta; but at maturity they are found loose in the pulp, e.g., tomato, grapes, brinjal, plantain, guava, papaya, etc. One seeded berry is found in date-palm, Artabotrys., etc.

There are a number of fruits of the berry or bacca type which show some variations from the normal type. These are noted in Table.

Tale -11.3 Different types of berry fruits

A comparative account between drupe and berry is given below in table.

When a fruit develops from a single flower with an apocarpous pistil, it is called aggregate fruit. Since the carpels are free each carpel gives rise to a simple fruit let.

Sometimes these fruitlets join together giving the appearance of a single fruit. In many other cases the fruits remain free from one another forming a bunch of fruits known as etaerio of fruitlets. Each fruitlet, an etaerio may be a follicle, an achene drupe or berry.

(i) Etaerio of follicles: Etaerio follicles are developed from apocarpous, muiti carpellary flower. It may be the development of paired fruits (e.g., calotropis and Vinca), three fruits (e.g., Aconitum), five fruits (e.g., Sterculia) and many

fruits (e.g., Mikhelia and Magnolia from a single flower with free or ocarpous pistil. In Mkhelia and Mag Ilia there are infinite numbers of carpels. As the flower matures, the thalamus elongates and the aggregate fruit looks like a branch of fruit. In the fruit of Asclepias, a special name has been given- conceptaculum. Here, the two follicles are united at the base.

(ii) Etaerio of achencs: This type of fruit is very common. These fruits are clustered together on a common thalamus. The fruitlets are provided with feathery persistent styles (e.g., Naravelia, Clematis) and occur in a group.

The achenes remain enclosed in a hollow, receptacular thalamus (e.g., rose) and occur on a flat top- shaped spongy thalamus (e.g., lotus). The minute achenes are buried as small brown specks on a fleshy edible thalamus of strawberry.

(iii) Etaerio of drupes:In this case, a number of small drupes or drupels, developing from separate carpels of a flower, are aggregated together on a fleshy tha- lamus, e.g., Raspberry.

(iv) Etaerio of berries: It develops from an apocarpous pistil lying embedded in the fleshy thalamus and grows into a single fruit (e.g., Anona). On the other hand, a group of distinct and separate berries are produced in Artabotrys and Polyalthia.

D. Multiple or composite fruits:

A multiple or composite type of fruit develops from a number of flowers (inflorescence). Such a fruit is also known as infructescence. Whole inflorescence with its component parts takes part in the production of fruit. These fruits are of two types.

(i) Sorosis: It is a multiple fruit developing from a spike or spadix. The whole infloresccnce forms a compact mass. The flowers fused together by their succulent tepals and ar- ranged on a thick club-shaped rachis.

The fertile fruits have edible juicy 1 perianth leaves and the bracts form more or less juicy chaffs around them.

The spinels like structures on the tough rind represent the stigmas of the carpels. The seed is covered by a membranous testa (e.g., Artocarpus, Morus and Pandanus). The edible part of’ the fruit is the fleshy and succulent perianth, flower and bracts. In Mom, fleshy perianths enclose dry achenes.

There are similar structures found in other cases, but the ovaries are not con­spicuous. e.g. Ananas comosUS (pineapple). The polygonal areas present on the surface represent united ovaries of the constituent flowers of the inflorescence. The sterile bracts present on the top of the fruit look like crown of small leaves.

(ii) Syconus:

The fruit is formed from the hypanthodium type of inflorescence. It is a hollow or pear shaped fleshy receptacle that forms the edible part of the fruit. The inflorescence giving rise to the fruit is also known as coenanthium. The female flowers within the closed receptacle of the inflorescence develop achenes, forming a multiple fruit of achenes, e.g., Ficus. A similar fruit is formed in which the coenanthium develops achenes on the open receptacle, e.g; Dorstenia.

Different parts of fruits are used as human food as noted in.