Notes On Sexual Reproduction in Plants - CBSE Class 10 Science

Sexual reproduction:  
This type of reproduction involves two organisms, the male and the female in the process of producing the offspring.  Sexual reproduction provides greater variations in the DNA thereby making the offspring adapted for better survival. Sexual reproduction ensures a mixing of the gene pool of the species. Due to genetic recombination, variations occur in the process of sexual reproduction.

Sexual reproduction in plants:
Plants reproduce sexually by producing male gametes in the form of pollen and the female gametes in the form of eggs.

Flower:
It is the main reproductive structure of a plant. A flower comprises sepals, petals, stamens and carpels.

       • Sepals and petals are considered to be the accessory whorls of the flower as they do not take part in the process of reproduction.
       • Stamens and carpels are the reproductive parts of a flower comprising germ cells. Germ cells help in the process of reproduction.
       • A unisexual flower contains either stamens or carpels. For example, papaya and watermelon are unisexual flowers.
       • A bisexual flower contains stamens as well as carpels. For example, hibiscus and mustard flowers are bisexual.
       • The stamen is the male reproductive organ that consists of filament and anther. The anther produces male gametes in the form of pollen grains.
       • The carpel is the female reproductive organ located at the centre of a flower. It consists of the ovary, style and stigma. The ovary is the swollen part at the bottom of the carpel. Ovary contains the female gametes in the form of eggs or ovules.

Pollination:
This is the transfer of pollen grains from the anther to the stigma of the carpel.

       • Different agents of pollination are wind, water, animals, birds, insects, human beings etc.
       • Petals attract insect or bird pollinators by their colour, scent, and nectar, which may be secreted in some part of the flower.
       • Two types of pollination are self-pollination and cross-pollination. Self-pollination involves the transfer of pollen grains from anther to the stigma of the same flower. Cross-pollination involves the transfer of pollen grains from anther of one flower to the stigma of another flower.
       • Pollen grains are trapped by sticky stigma during the process of pollination.
       • Pollen grains germinate on the stigma to give rise to pollen tube which aids in the process of fertilisation.

Fertilisation:
This involves the fusion of male germ cell with the female germ cell resulting in the formation of a single cell, the zygote. This process is also called as syngamy.

       • There occur many changes after fertilisation.  After fertilisation, the zygote divides repeatedly to form an embryo which resides inside the seed.
       • The ovule develops into a seed.
       • The ovary ripens to form a fruit.
       • Seed inside the fruit encloses the embryo, the future plant.

Germination:
It is the growth of an embryonic plant residing inside the seed under favourable conditions.  It results in the formation of a new seedling which further grows into a new plant. The factors essential for germination are nutrients, water and proper temperature. Seed has an embryo protected by reserved food materials in the form of cotyledons and also an outer covering called as seed coat.

Summary

Sexual reproduction:  
This type of reproduction involves two organisms, the male and the female in the process of producing the offspring.  Sexual reproduction provides greater variations in the DNA thereby making the offspring adapted for better survival. Sexual reproduction ensures a mixing of the gene pool of the species. Due to genetic recombination, variations occur in the process of sexual reproduction.

Sexual reproduction in plants:
Plants reproduce sexually by producing male gametes in the form of pollen and the female gametes in the form of eggs.

Flower:
It is the main reproductive structure of a plant. A flower comprises sepals, petals, stamens and carpels.

       • Sepals and petals are considered to be the accessory whorls of the flower as they do not take part in the process of reproduction.
       • Stamens and carpels are the reproductive parts of a flower comprising germ cells. Germ cells help in the process of reproduction.
       • A unisexual flower contains either stamens or carpels. For example, papaya and watermelon are unisexual flowers.
       • A bisexual flower contains stamens as well as carpels. For example, hibiscus and mustard flowers are bisexual.
       • The stamen is the male reproductive organ that consists of filament and anther. The anther produces male gametes in the form of pollen grains.
       • The carpel is the female reproductive organ located at the centre of a flower. It consists of the ovary, style and stigma. The ovary is the swollen part at the bottom of the carpel. Ovary contains the female gametes in the form of eggs or ovules.

Pollination:
This is the transfer of pollen grains from the anther to the stigma of the carpel.

       • Different agents of pollination are wind, water, animals, birds, insects, human beings etc.
       • Petals attract insect or bird pollinators by their colour, scent, and nectar, which may be secreted in some part of the flower.
       • Two types of pollination are self-pollination and cross-pollination. Self-pollination involves the transfer of pollen grains from anther to the stigma of the same flower. Cross-pollination involves the transfer of pollen grains from anther of one flower to the stigma of another flower.
       • Pollen grains are trapped by sticky stigma during the process of pollination.
       • Pollen grains germinate on the stigma to give rise to pollen tube which aids in the process of fertilisation.

Fertilisation:
This involves the fusion of male germ cell with the female germ cell resulting in the formation of a single cell, the zygote. This process is also called as syngamy.

       • There occur many changes after fertilisation.  After fertilisation, the zygote divides repeatedly to form an embryo which resides inside the seed.
       • The ovule develops into a seed.
       • The ovary ripens to form a fruit.
       • Seed inside the fruit encloses the embryo, the future plant.

Germination:
It is the growth of an embryonic plant residing inside the seed under favourable conditions.  It results in the formation of a new seedling which further grows into a new plant. The factors essential for germination are nutrients, water and proper temperature. Seed has an embryo protected by reserved food materials in the form of cotyledons and also an outer covering called as seed coat.

Videos

Activities

Activity 1
Mrcbiology.com has put across detailed information about sexual organ, the flower in a plant body. It has demonstrated the structure of flower with all the enclosed parts. Individual role of each part in the process of sexual reproduction is elucidated. Processes like pollination, fertilisation and seed formation are explained. In addition to the audio, text is provided on a slide to make the information more clear.
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Activity 2
Skoool.ie has compiled a wonderful animated audiovisual version to show different steps involved in the process of sexual reproduction in plants . User needs to follow the indications given by the interface and click on the necessary numbers given on the buttons. Activities and exercises in between are added flavours of the content. Glossary represented is informative and brings in all the key terms related to the concept of sexual reproduction in plants.  
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References

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