Pollen tube and fertilisation sim
Brush pollen onto a flower's stigma, drag the pollen tube down a cut-away carpel model one hour at a time while you record its length, then drag the male nucleus onto the female nucleus and see the ovule become a seed.
Sexual reproduction in flowering plants: pollination onto the stigma, the pollen grain growing a pollen tube down through the style and into the ovule through the micropyle, fertilisation as the fusion of the male gamete nucleus with the female gamete nucleus to make a zygote, the order of these events, and the ovule becoming the seed and the ovary the fruit · covers the O-Level, IGCSE topic
What the sim shows
Pollen tube and fertilisation: a brush moves pollen onto the stigma of a teaching-model flower (pollination). A cut-away carpel model beside it, and the close-up below, show what happens next inside the carpel: a pollen grain grows a pollen tube down through the style and across the ovary; the tube enters the ovule through the micropyle; its tip bursts and the male gamete nucleus fuses with the female gamete nucleus (fertilisation), making a zygote. The ovule then becomes a seed and the ovary a fruit. Simplified on purpose: the flower is a teaching model, about 3 times life size, and the cut-away carpel model beside it is about 5 times life size, with only one ovule shown (a real ovary often holds many); the pollen grains, the tube and the nuclei are drawn far larger than true scale so they can be seen; the tube grows at a steady 1.5 mm per hour along an 18 mm path, so it takes 12 hours; these numbers are illustrative: real tubes grow at very different speeds, from under 1 mm an hour to about 1 cm an hour (maize); only one pollen grain grows a tube; on a real stigma several may, and each tube can reach a different ovule; a real pollen tube carries two male nuclei: one fuses with the female gamete nucleus; the other joins other nuclei in the ovule to start the seed's food store, which the syllabus does not ask for; time moves in steps of one hour, only when you drag or press Wait; after fertilisation the change to seed and fruit (weeks in a real plant) is shown in one step.
- Glow: what to drag next
- Close-up: the carpel model's face and the ovule (not to scale)
- Box: the part drawn 4 times larger in the ovule close-up
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