Answer: Chemotropic signals from the ovule (LURE peptides secreted by synergid cells guide pollen tube).
- A Random diffusion through the stylar tissue matrix without any clear directional molecular cue present
- B Chemotropic signals from the ovule (LURE peptides secreted by synergid cells guide pollen tube)
- C Gravitropic sensing of the gravitational field acting specifically within the elongated style tissue
- D Wind direction sensed by specialized mechanoreceptors supposedly located at the pollen tube tip
Correct answer: B. Chemotropic signals from the ovule (LURE peptides secreted by synergid cells guide pollen tube)
Explanation: Pollen tube guidance: LURE peptides (CRP proteins) from synergid cells of the embryo sac attract and guide the pollen tube through the style toward the micropyle of the ovule.
Double fertilisation in angiosperms: one male gamete fuses with the egg to form the diploid zygote (syngamy), while the second fuses with the two polar nuclei to form the triploid primary endosperm nucleus (triple fusion). Image: Triploid, CC BY 3.0, via Wikimedia Commons.
Concept context
Flower structure, pollination, double fertilization, and seed/fruit development - the highest-scoring Class 12 biology chapter in NEET.
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