describe briefly the steps in fertilization according to 7th class science
Answers
When pollen grain lands on the stigma of the suitable flower, it makes a tiny tubule through style to the ovary. The pollen grain carries male gamete which meets the female gamete in the ovule and fertilization takes in flowers. The cell which results after fusion of the gametes is called a zygote which further develops into embryo.
Step 1: Pollination
In general, male gametes are contained in pollen, which is carried by wind, water, or wildlife (both insects and animals) to reach female gametes. The pollen is deposited on a plant's stigma, which is part of the pistil (the elongated part of a flower extending from the ovary). This process is called pollination.
Step 2: Germination
Within a few minutes, pollen tubes begin growing, or germinating, toward the egg cell. These tubes will provide a path for the sperm carried in the pollen to reach the egg.
Step 3: Penetration of the Ovule
The pollen tubes penetrate the ovule, which contains the female gametes.
Step 4: Fertilization
Sperm travel down the pollen tubes and fertilize an egg. Most angiosperms undergo double fertilization, where both an egg and the polar nuclei in the embryonic sac are fertilized.