Explain in detail the process of double fertilization in a flowering plant, including the roles of the two sperm cells, the formation of zygote and endosperm, and the significance of this process for seed development.
Answer
Double fertilization involves the pollen tube delivering two sperm cells to the ovule; one sperm fertilises the egg cell forming a diploid zygote, while the other sperm fertilises the two polar nuclei of the central cell forming a triploid endosperm nucleus; the zygote develops into the embryo and the endosperm nourishes it, synchronising seed development with fertilisation.
Step-by-step solution
- Pollen tube penetrates the transmitting tract and reaches the ovule.
- Two sperm cells are delivered inside the tube.
- One sperm fuses with the egg cell, forming a diploid zygote that will become the embryo.
- The other sperm fuses with the two polar nuclei of the central cell, creating a triploid endosperm nucleus.
- The zygote develops into the embryo, while the endosperm undergoes divisions to form nutritive tissue.
- Double fertilisation synchronises seed development with fertilisation, ensuring resources are invested only in fertilised ovules.
Common mistake: Confusing which sperm fertilises which cell
Concept tested: Double fertilization mechanism in angiosperms
Published · How this solution was prepared and checked
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