Trace the events that would take place in flowers from the time of fall of pollen grain on stigma up to completion of fertilization with the help of diagram.
Show Hint
Double fertilization in flowering plants results in the formation of both a zygote and a triploid endosperm.
Step 1: Pollen Grain Landing on Stigma.
- The process of fertilization begins when a pollen grain lands on the stigma of a flower. The stigma is sticky, allowing the pollen to adhere.
Step 2: Germination of Pollen Grain.
- The pollen grain germinates on the stigma, forming a pollen tube that grows down the style toward the ovary.
Step 3: Growth of Pollen Tube.
- The pollen tube grows through the style, carrying two sperm cells. It is guided by chemicals released from the ovule.
Step 4: Entry into Ovule.
- The pollen tube enters the micropyle of the ovule. The tube releases two sperm cells into the ovule.
Step 5: Double Fertilization.
- Double fertilization occurs: one sperm cell fuses with the egg cell to form a zygote, while the other sperm cell fuses with the polar nuclei to form the triploid endosperm.
Step 6: Fertilization Complete.
- After fertilization, the zygote develops into an embryo, and the ovule develops into a seed. The fertilized ovary develops into a fruit.
Final Answer:
Fertilization in plants involves pollen grain germination on the stigma, the growth of the pollen tube, double fertilization, and the development of seeds and fruits.
