Reproduction In Plants

Binary fission is the method of reproduction in unicellular organisms where their body splits into two equal halves and then they grow independently. This type of reproduction is common in bacteria and amoeba.

Sexual reproduction is the process of reproduction in which two gametes (male and female) are involved which fuses to reproduce their offspring. In plants, fusion is possible only if gametes are brought together. So in order to bring gametes together pollination (transfer of gametes from one plant to another) takes place. Therefore pollination is the first step of sexual reproduction in plants.

Zoospores are mobile spores, thick-walled vegetative cells in algae are Akinetes and aplanospores are thin-walled non-motile spores in algae.

Aggregate fruits are the fruits which are developed from a single flower, multi carpellary (more than three carpels), apocarpous (distinct carpels) and a superior ovary. E.g. Polyalthia.

Micropyle is the small opening through which the pollen tube enters the embryo sac and transports the male gamete to the female gamete. After this the process of fertilization takes place.

Pericarp is made of 3 layers epicarp- the outer layer, mesocarp- the middle layer and endocarp- the inner most layer. In mango the inner most layer that is endocarp is hard like stone. So, due to hard endocarp mango is also known as stone fruit.

The rudimentary root portion is known as radicle and rudimentary stem portion is known as plumule.

The mesocarp of coconut is fibrous. Dispersal of seeds and fruits involves different types of mechanisms. Dispersal of xanthium fruits are because of animals as their fruits have sharp pointed hooks, bracts etc.

Function of endosperm is to provide nutrition.

As the same flower is involved in self-pollination so number of seeds which could be transferred will be less.

In sexual reproduction two gametes are required which are male and female. So these gametes are present in stamen (which have male gametes) and pistil (which have female gametes) which are part of a flower only.

Androecium and gynoecium are the male and female reproductive part of the flower which are responsible for carrying the sexual reproduction in plants. Whereas calyx are the sepals which protect the flower in its early stages and corolla are the petals which are coloured part of plant which attracts the insects to carry out the process of pollination.

In cross-pollination transfer of pollen grains takes place from one flower to another which increases the chances of forming new varieties, plants with plant growth and more viable seeds.

Anemophily is pollination due to the wind. In this case, flowers are small in size, and do not have a smell or are not attractive. Pollens are light and non-sticky. E.g. grass, maize etc.

Entamophily is pollination with the help of insects like butterfly, honey bees etc. So to attract these insects flower has to be attractive this could be possible only with colorful petals and nectar secretion.

After fertilization ovule changes into seed, ovary into fruit, pericarp becomes the fruit wall and endosperm provides the nutrition.

Mango is stone fruit, apple is true fruit and cryopsis is single seed dried fruit like corn etc.

Follicles resembles legume whereas regma develops from ovary.

Vegetative propagation is the process of forming offspring from the pre-existing structures like roots, stems etc. It is generally of two types budding and fragmentation. Budding can be seen in Hydra and fragmentation can be seen in spirogyra.

(i) Bryophyllum: - Budding. In budding new offspring are produced through the buds which are repetitive cell division at one spot.

(ii) Spirogyra: - Fragmentation. In fragmentation, main plant body or parent body gets divided into small fragments which later develops into an individual plant.

Pollination → fertilization → seed formation → dispersal of seeds.

With the help of pollination, gametes are transferred and brought together which are later fertilized. After fertilization seed formation takes places which are later dispersed with the help of various mechanisms.

Pollination is the transfer of pollen or male gametes from the anther of one flower to the stigma of an other or same flower. It is the first step in the process of sexual reproduction. It is of two types:

(i) Self-pollination: - Also known as autogamy. In this, both male and female gametes are of the same flower. E.g. peas, sunflower etc.

(ii) Cross-pollination: - Also known as allogamy. In this pollens are transferred from anther of one flower to stigma of another flower with the help of wind, water or insects. E.g. Legumes, grass etc.

After the process of pollination, a male gamete is transferred to the stigma of the flower. After the transfer, pollen tube is formed which carries the male gamete to the female gamete. Then male and female gametes get fused to form a fertilized egg known as a zygote. This process of fusion is known as fertilization.

(i) Entamophily- Pollination with the help of insects like butterfly and honeybee. To attract these insects, flower has to be of bright color with scent and nectar glands. E.g. Rose etc.

(ii) Anemophily- Pollination with wind is known as anemophily. For the transfer of pollen with the wind, pollen has to be dry, light weight and powdery. And to catch these pollens stigma needs to be feathery. E.g. grass, maize etc.

(i) Fusion of male gamete (n) and an egg (n) to form the zygote (2n) is known as fertilization. Nuclear is Haploid that is 2n.

(ii) Fusion of male gamete (n) with the secondary nucleus (2n) to form an endosperm nucleus (3n) is triple fusion. And the nature of nucleus formed in triploid that is 3n.

Monocotyledons: - Seeds with single cotyledon are known as monocotyledon. E.g. maize, rice etc. Their leaf have parallel venation.

Dicotyledons: - Seeds with two cotyledons are known as dicotyledons or dicots. E.g. Bean etc. Their leaf generally have reticulate venation.

(i) By birds: - Tomato and guava. These seeds are eaten with the edible portion and later excreted out. They have protective layer which protects the seeds from digestive juices.

(ii) By human beings: - Rubber and Eucalyptus.

There are two male gametes. One male gamete fuses with the egg to form a zygote. This fusion between male and female gametes is known as fertilization. And the second male gamete fuses with secondary nucleus to form the endosperm nucleus. This process of fusion of male gamete with egg and secondary nucleus is known as double fertilization.

1^st male gamete (n) + Egg(n) → Zygote (2n)

2^nd male gamete (n) + Secondary nucleus (2n) → Endosperm nucleus (3n)

Fusion of male gamete with the secondary nucleus to form endosperm nucleus is known triple fusion. This is known as triple fusion because in this two polar nuclei fuse with the male gamete hence the result (endosperm nucleus) which we get after fusion is triploid in nature.

2^nd male gamete (n) + Secondary nucleus (2n) → Endosperm nucleus (3n)

Figure A is the gynoecium or the female reproductive part of flower. Stigma, style and ovary are the parts of gynoecium.

Figure B is the fruit.

Fruit is nothing but the modified ovary.

(i) whole inflorescence

(ii) Aggregate fruits

Ramu went to the along with his father. He sowed mustard seeds in the soil. Aster a few days he observed the process of germination. The seeds grew into plants and produced a flower. On maturity, these flowers produced pollen grains that were transferred to the stigma by pollination. The male gametes fused with the female gametes during the process of fertilization.

Fibrous mesocarp helps in hydrochory in coconut seeds because the fibrous layer is easily carried out by the water to other places.

(i) By the process of fertilization the fruit is developed. Fertilization is the process of fusion of male and female gametes to form the zygote.

(ii) Development process:-

1. Germination of pollen grains: - by the process of pollination pollen grain when lands on suitable stigma. Pollen has 2 cells. One is vegetative cell and other is a generative cell. Vegetative cell forms the pollen tube which carries the generative cell which later gets divided into 2 male gametes.

2. Fertilization: - through micropyle pollen tube enters the embryo-sac and releases the male gametes in it. Then fusion between male and female takes place which forms the zygote. This process of fusion is known as the fertilization.

3. Triple fusion: - Fusion of male gamete with the secondary nucleus to form endosperm nucleus is known triple fusion. This is known as triple fusion because in this two polar nuclei fuse with the male gamete hence the result (endosperm nucleus) which we get after fusion is triploid in nature.

4. Double fertilization: - There are two male gametes. One male gamete fuses with the egg to form a zygote. This fusion between male and female gametes is known as fertilization. And the second male gamete fuses with secondary nucleus to form the endosperm nucleus. This process of fusion of male gamete with egg and secondary nucleus is known as double fertilization.

5. Post- fertilization changes: - (A) ovule → seeds

(B) Integuments → seed coats

(C) Ovary → Fruit.

(iii)

Two events involved in the sexual reproduction of a flowering plant are pollination and fertilization.

Pollination is the process of transfer of pollen from the anther to the stigma of the flower. It is of two types – Self-pollination and cross-pollination.

Self-pollination: - In self-pollination, pollen from the anther of one pollination lands on the stigma of same flower. It is also known as autogamy. E.g. Wheat, barley etc.

Advantages: - 1. Pollination does not depend on other agents.

2. no pollen wastage.

Disadvantage: - 1. No new variety.

2. new plants are weak.

Cross- pollination: - In cross-pollination pollen from anther of one flower lands on the stigma of another flower by the means of water or animals or wind. It is also known as allogamy. E.g. grasses etc.

Advantages: 1. Seeds are viable.

2. New varieties are produced.

- (i) Parthenocarpic fruits are the fruits which are produced without the process of fertilization. E.g. seedless grapes, guava etc.

The structure is given below:

1. Dicot seed is bulky.

2. The short longitudinal structure is known as raphae.

3. Micropyle or the grem pore is present at the end of raphae.

4. Seed coat encloses the embryo.

5. Cotyledons are attached to the primary axis.

6. Primary axis has rudimentary root called radicle and rudimentary stem called plumule.

The diagram of monocot 1. Very thin seed coat.

2. Fruit wall thin and fused with the seed coat.

3. Fruit covered with chaff which is yellowish bracteoles.

4. The embryo has scutellum which is single cotyledon and a shoot axis.

5. The lower part has radicle and has coleorhiza.

6. The upper part has plumule and a sheath which covers it known as coleoptile.

- (i)

A. Petals

B. Stigma

C. Style

D. Stamen

E. Ovary

F. Ovules

G. Sepals

(ii) After fertilization Ovary changes into fruits and ovary into seeds.

(i) Binary fission. In binary fission, parent divides into two parts which later develops into independent individuals.

(ii) Amoeba.

(iii) No, this method does not favour variation. Because in this type of reproduction, offspring have the similar characteristics of parents.

- The bee will visit- Jasmine, nerium, gulmohar, rose, lotus, chrysanthemum, dahlia, and peas because they have attractive petals, scented flowers and nector as attraction.

Due to presence of these characteristics entamophily that is pollination with the help of insects is possible.

- (i) Pollination in field ‘A’ Self-pollination.

Pollination in field ‘B’ Cross-pollination.

(ii) Field B will have higher yield as it has cross-pollination. Peas generally have cross pollination for transfer of pollen.

(iii) Farmer should use seeds from field B because it may have some new varieties and also seeds will be more viable because of cross-pollination.

The diagram for cross pollination and self pollination is shown below:

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The diagram is shown below:

(i) Endospermic part which is white in color is edible.

(ii) Coconut has fibrous mesocarp for the fruit dispersal by the water.

(iii) It is protective and it can be used in making ropes.

- (i)

(ii) Yes, there is a relation between distance travelled and efficiency of dispersal. More the seed dispersal more is the efficiency.

(iii) It shows that seed dispersal and time took are directly proportional. If seeds are light weighed then it will cover more distance.

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I. Achene – Mirabilis

II. Caryopsis - paddy

III. Cypsela - Tridax

IV. Nut - Cashew

V. Cremocarp - coriander

VI. Lomentum - Acacia

VII. Regma - castor

VIII. Loculicidal capsule - cotton

IX. Septicidal capsule – Lady’s finger

X. Follicle - calotropis

XI. Legume – Beans and peas

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1) Dry indehiscent fruits are one of the types of dry fruits, those in which there isn’t a seedpod which open is known as indehiscent fruits.

2) Fleshy fruits are fruits that have fleshy parts as its main. They are simple, aggregate or multiple in which they come out from the ovary. Berries, Pine etc are the examples.

3) Schizocarpic Fruit is a subtype of indehiscent fruits consisting of two carpels which at maturity separate along the midline into two one-seeded halves, each of which is indehiscent. Eg. Mimosa, maple, coriander, hollyhock.

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i. Radicle

ii. Plumule

iii. Cotyledon

iv. Seed coat

v. Micropyle

The diagram is

- Pollination is of two types – Self-pollination and cross pollination.

Self-pollination: - In self-pollination, pollen from anther of one pollination lands on the stigma of same flower. It is also known as autogamy. E.g. Wheat, barley etc.

Cross- pollination: - In cross-pollination pollen from anther of one flower lands on the stigma of other flower by the means of water or animals or wind. It is also known as allogamy. E.g. grasses etc.

Cross pollination is more advantageous because in this type of pollination there are chances of formation of new varieties of seeds and more viable seeds. Along with this there are chances that bad characters of the parent plant may get eliminated and won’t pass to next generation.

- Self-pollination: - In self-pollination, pollen from anther of one pollination lands on the stigma of same flower. It is also known as autogamy. E.g. Wheat, barley etc.

Advantages: - 1. Pollination does not depend on other agents.

2. no pollen wastage.

Disadvantage: - 1. No new variety.

2. new plants are weak.

Pollination is the process of transfer of pollen from the anther to the stigma of the flower. It is of two types – Self-pollination and cross-pollination.

Biotic factors:- In biotic factors, there is need to attract the pollinators to carry the process of pollination. Insects, animals, and birds are some of the biotic factors.

Abiotic factors: - In this, there is no need to attract the pollinators for the process of pollination. Wind and water are abiotic factors.