Pollination and fertilization are distinct processes in plant reproduction. Pollination is the transfer of pollen from the anther to the stigma, while fertilization is the fusion of male and female gametes within the ovule. Fertilization occurs in the ovule, and the product is a zygote, which develops into the embryo within the seed.
1. Pollination:
Definition: Pollination is the transfer of pollen grains from the anther (male part) to the stigma (female part) of a flower.
Purpose: To deliver the male gametes (sperm) to the female ovule for fertilization.
Mechanism: Pollen grains are transferred by various agents like wind, water, insects, birds, etc.
2. Fertilization:
Definition: Fertilization is the fusion of the male and female gametes (sperm and egg) within the ovule to form a zygote.
Purpose: To initiate the development of a new plant embryo within the seed.
Mechanism: After pollination, the pollen grain germinates on the stigma and forms a pollen tube that grows down through the style to the ovary. The pollen tube enters the ovule through the micropyle, and the sperm cells fuse with the egg cell, resulting in a zygote.
3. Site of Fertilization:
Fertilization takes place within the ovule, which is located inside the ovary of the flower.
4. Product of Fertilization:
The product of fertilization is a zygote, which is a diploid cell (containing two sets of chromosomes) that develops into the embryo within the seed.
5. Diagram of Pistil with Pollen Tube Growth:
A diagram of a pistil showing pollen tube growth and entry into the ovule would typically include the following:
Stigma: The receptive surface at the top of the pistil where pollen grains land.
Style: The elongated structure connecting the stigma to the ovary.
Ovary: The swollen base of the pistil containing the ovules.
Ovule: The structure within the ovary that contains the egg cell.
Pollen Tube: A tube-like structure that grows from the stigma down through the style and into the ovule.
Micropyle: A small opening in the ovule where the pollen tube enters.
Pollen Tube Growth: The pollen tube is shown growing down through the style and entering the micropyle of the ovule.
Male Gametes: The sperm cells are shown traveling down the pollen tube.
In summary, pollination is the transfer of pollen, while fertilization is the fusion of gametes, resulting in the formation of a zygote within the ovule of a flower.