Sexual Reproduction
-> The production of new organism by the help of gametes of both parents (male and female) is called sexual reproduction. It is the source of recombination.
Note:- Generally flowering plants are reproduced by sexual reproduction.
Sexual reproduction in plants
Some important points are:-
-> The special reproductive cells which take part in sexual reproduction is called sex cells or gametes.
There are two types of gametes- (i) Male gametes (ii) Female gametes
-> When male and female gametes fuses together then they formed a new cell known as zygote. It is also called a germ cell.
-> The flowers which contain either male organ or female organ are called unisexual flowers and the flowers which contain both male organ and female organ are called bisexual flowers.
e.g. Corn, papaya and cucumber produce unisexual flowers, whereas mustard, rose and petunia have bisexual flowers.
Note:- Most of the flowering plant has both male and female organs in the same flower so they are bisexual in nature.
Male organ of flowering plant is called stamen and male gametes are present in pollen grains Whereas Female organ of flowering plant is called carpel and female gametes are present in ovules or ova or egg cells or eggs.
Parts of flowers
Main parts of flower are:-
(i) Receptacles (ii) Sepal (iii) Stamen (iv) Petal (v) Carpel
* Receptacle- The base of the flower to which all the parts of flower are attached is called receptacle.
* Sepal- The green structure present at the outermost part of a flower called sepal.
Function- It protect the flower in its initial stage (bud).
* Petals- The colourful part of the flower is called petals. It lies inside the sepals.
Function- (i) it is used to attract insects.
(ii) It also protect the reproductive organ which are present at the centre of the flower.
* Stamen- The leaf stalk with swallow tops just inside the petal called stamen. The stock of stamen is called filament and swallow tops of a stamen is called anther.
Note:- In anther, pollen grains are stored. They are yellow powder like substance to us.
Function- It help to release pollen grains.
* Carpel- Flask shaped organ present at the centre of the flower is called carpel.
They are divided into three parts:-
(i) Stigma- The top part of the carpel is called stigma.
Function- * It receive the pollen grains from anther of stamen.
* It is sticky in nature So, the pollen grains get stick to it.
(ii) Style- The middle part of the carpel is called style. It is a tube which connects stigma to ovary.
Function- It helps to transport the pollen grains from stigma to ovary.
(iii) Ovary- The swollen part present at the bottom of carpel is called ovary.
Function- It make ovules and store them.
Fertilisation in Plants
-> The process by which a male gamete fuses with female gamete is called fertilization. In plants, pollination takes place.
Notes
* A seed is the reproductive unit of plant and can be developed in a new plant. The part of a baby plant in seed which develop into shoot with leaves is called plumule and the part which develops into root is called radicle.
* Dormant state- When a baby plant which present inside the seed is in the inactive state then this state is called dormant state.
e.g. mustard seeds, gram, peas, etc.
Explanation:- In pollination of flowering plant, male gamete moves down in the pollen tube of carpel and enters in the ovules and finally reaches in the ovary. As a result, the male gamete fuses with nucleus of female gametes and formed a new cell called zygote or fertilized egg.
As the time increases, zygote developed in embryo and finally in seed. After that, The seed begins to grow in new plant and this process is known as germination of seed. In this process, the dormant seeds developed into new plants after getting water, air, warmth, etc. Seed begins to absorb water and as a result, they swells and burst the seed coat.
The water helps the enzymes to function of seeds and digest their stored food in cotyledons. This helps the seeds in the formation of radicle and plumule and produce new baby plant.
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