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Gametogenesis. As you are already aware gametogenesis refers to the process of formation of the two types of gametes-male and female. Gametes are haploid cells. In some algae, the two gametes are so similar in appearance and hence are called homogametes (isogametes). That it is not possible to categorize them into male and female gametes. However, in a majority of sexually reproducing organisms the gametes produced are of two morphologically distinct types (heterogametes). In such organisms the male gamete is called the antherozoid or sperm and the female gamete is called the egg or ovum.

 Types of gametes : (a) isogametes of Cladophora (b) heterogametes of Fucus (alga) and (c) human beings

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Vegetative propagation is defined as formation of two or more new offsprings from any vegetative part of plant. in Vegetative Propagation parts like Rhizome , buds, tuber , leaves , roots and stem give rise to new plants . these parts are called as Vegetative propagules It is very rapid method.

It is of two types :

A. Natural Vegetative propagation

1. Vegetative propagation by stem. e.g. grasses, turmeric, onion, colocasia, potato, gladiolus and crocus.

2. Vegetative propagation by roots. e.g., Tuberous roots of sweet potato, asparagus, tapioca, dahlia and yams (Dioscorea).

3. Vegetative propagation by leaves e.g. Bryophyllum, Begonia, Lilium.

4. Vegetative propagation from reproductive organs. Flower buds of century plant (Agave sp.) develop into bulbils.

B. Artificial vegetative propagation.

1. Cutting e.g. leaf cutting in Bryophyllum.

2. Layering e.g. Jasmine.

3. Grafting e.g. Rose, Mango.

4. Micro-propagation.

5. Gootee e.g. lemon, orange, guava, litchi

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Importance of vegetative propagation

(1) Plants produced by vegetative propagation are genetically similar and constitute a uniform population called as clone.

(2) Plants that have reduced power of sexual reproduction, long dormant period of seed, poor viability can be  multiplied by vegetative methods.

(3) Some fruit trees like banana, pineapple  that do not produce viable seeds and dub grass which produces small quantity of seeds can  be  propagated by vegetative methods.

(4) It is a rapid and easier method of propagation.

(5) Good characters can be  preserved by vegetative propagation.

(6) Vegetative Propagation can be used to develop Virus Free plants.

(7) Grafting helps in getting an economically important plant having useful characteristic of  two different individuals in short time in a single plant.

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D.

(D) seed coat.

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Basic features of sexual reproduction

(1) Gametogenesis( by meiosis) -Development of male and female gametes which are haploid in nature .

(2) Fertilization- Fusion of the two gametes (haploid cells) to form zygote (diploid cell).

(3) Embryogenesis- Mitotic divisions and cell differentiation of zygote to form embryo. mitosis helps in increasing the cell number and differentiation helps to form specialized tissues and organs.

(4) Development - Growth  of embryo to form new individual.