Notes, Exercises, Videos, Tests and Things to Remember on Sexual Reproduction in Plants
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The process of reproduction in which the fusion of male and female gametes is essential is called sexual reproduction.
Male reproductive cell (undergo meiosis) ---> male gamete (sperm) Female reproductive (undergo meiosis) ---> female gamete (egg)Sperm and Egg (fuse in a process called fertilization) ---> zygote (undergo mitosis) ---> embryo (undergo mitosis) ---> new individual
Chlamydomonas reproduces sexually by producing isogametes. Isogametes are gametes that are indistinguishable with each other i.e. male and female gametes are similar in shape, size and in other respects too. The process of reproduction where the formation of isogametes takes place is called conjugation.
In Chlamydomonas, two individuals form similar gametes. One of them behaves as male gamete and another behave as the female gamete. They are attracted towards each other and mingling of these gametes takes place (fertilization). After fertilization, the zygote is surrounded by a layer. Then the zygote divides into four by mitosis. The cover bursts and new Chlamydomonas come out of it.
Some Definitions: Flower: It is the reproductive part of the plant.
Unisexual flowers: Those flowers, which contain only three parts of the flower and lack one part either androecium or gynoecium, are called incomplete flowers.
Staminate flowers: Those flowers that lack gynoecium but contain calyx, corolla and stamen are called the staminate flower.
Pistillate flowers: These flowers have calyx, corolla and gynoecium but lack androecium. They are also called the female flower.
Bisexual flower: That flower which has all four parts, calyx, corolla, androecium and gynoecium, are called the bisexual flower.
Pollination: The process of transfer of pollen grains from the anther to stigma of a same or different flower is called pollination.
Self-pollination: The pollination (the process of transfer of pollen grains) that occurs in the same flower is called self-pollination. This type of pollination only occurs in the complete flower. No natural agents like air, water or insect is required for this process.
Cross-pollination: The pollination (the process of transfer of pollen grains) that occurs between two flowers is called cross-pollination. This occurs in both unisexual and bisexual flower. The external agents like bee, air, other insects, water etc. are required.
The reproductive part of a plant is flower. It contains androecium as male reproductive part and gynoecium as female reproductive part. After maturity androecium, produce pollen grains as male gamete and gynoecium produce ovule as a female gamete. After maturation of gamete, pollination takes place. The pollination may be self or cross. After pollination, the fusion of male and female gamete takes place. This process is called fertilization and a fertilized ovum is called zygote. The zygote then undergoes mitosis and form embryo. The plant embryo is called a seed. If seed encounters favorable environment it germinates to become a new plant.
|1. It is the process of transfer of pollen grains from the anther to the stigma of a flower.||1. It is the process of fusion of male and female gamete.|
|2. It occurs before fertilization.||2. It occurs after pollination.|
|3. It occurs only in plants||3. It occurs in both plants and animals.|
1. It is smaller in size.
2. It is highly active.
1. It is bigger in size.
2. It is inactive.
i. It occurs when pollen grain from anther of a flower are transferred to stigma of the same flower or another flower on the same plant.
ii. New species and varieties of plants are not produced.
i. It occurs when pollen grain from anther of a flower are transferred to stigma of a flower on the other plant of the same species.
ii. New species and varieties of plants are produced.
1. It is formed due to the fusion of male gamete and two polar nuclei.
2. It is triploid (3n) in nature.
1. It is formed due to the fusion of male gamete and an ovum.
2. It is diploid (2n) in nature.
The transfer of pollen grain from the anther to stigma of pistil is called pollination. In self-pollination, the pollen grains are transferred from the stamen of one flower to the pistil of the same flower or another flower on the same plant. On the other hand, in cross pollination, the pollen grains are transferred from one flower to another flower on a different plant of the same species.
In sexual reproduction of plants, a pollen grain gives rise to male gametes. One male gametes fuses with the egg while the other fuses with the polar cells. As there are two male gametes and fertilization takes place at two places, it is called double fertilization.
The process of reproduction where formation of isogametes takes place is called ______.