All six ovules of a flower are fertilised…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
All six ovules of a flower are fertilised. In each ovule, double fertilisation takes place in the usual way.
- How many male gametes are used?
- How many zygotes are formed?
- How many haploid nuclei fuse to make all the primary endosperm nuclei?
Need a reminder? The key ideaShow
One male gamete fuses with the egg and makes the zygote, . The other fuses with the two polar nuclei and makes the primary endosperm nucleus (PEN), . The two polar nuclei and the egg come from the same megaspore, so they are alike, and the two male gametes are alike. The PEN divides by mitosis, first with free nuclei and later with walls.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. ovules, each with double fertilisation.
Plan. Count what happens in one ovule, then multiply by .
Step 1. Male gametes. .
Step 2. Zygotes. One in each ovule, so .
Step 3. Haploid nuclei in the PENs. Each PEN has of them: .
Answer: ; ; .
Check. The male gametes are shared out: go to the eggs and to the polar nuclei.
Watch out. One pollen grain gives two male gametes, so six pollen tubes are enough.
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