Describe the sequence of cellular events that occurs in the pollen tube after it has emerged from the stigma but before it reaches the ovule. Include the key signals and structures involved.
Answer
Pollen grain germinates, forms a pollen tube that elongates through the style guided by pollen tube attractants and cell wall components, reaches the micropyle of the ovule, and delivers sperm cells to the embryo sac.
Step-by-step solution
- After landing on the stigma, the pollen grain absorbs water and germinates.
- A pollen tube forms at the germination site and starts to elongate.
- The tube is guided by chemical signals (e.g., attractants such as LURE peptides) and structural cues from the style.
- It penetrates the transmitting tract and reaches the micropyle of the ovule.
- The pollen tube then delivers the two sperm cells to the embryo sac for fertilization.
- This sequence ensures successful delivery of sperm cells for fertilization and seed formation.
Common mistake: Assuming pollen tube grows randomly without guidance signals
Concept tested: Pollen tube guidance
Published · How this solution was prepared and checked
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