Explain the sequence of cellular events from pollen tube arrival at the ovule to the formation of the zygote and the endosperm in a flowering plant.
Answer
Pollen tube arrives at ovule, releases two sperm nuclei; one fertilises the egg to form a zygote, the other fertilises the two polar nuclei to form the endosperm.
Step-by-step solution
- Pollen grain lands on stigma and germinates, forming a pollen tube.
- Pollen tube grows through style to reach the ovule’s micropyle.
- Pollen tube releases two sperm nuclei into the ovule.
- One sperm nucleus fuses with the egg cell, forming the diploid zygote.
- The second sperm nucleus fuses with the two polar nuclei, forming the triploid endosperm.
Common mistake: Assuming a single sperm fertilises both the egg and endosperm
Concept tested: Double fertilisation
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