In a plant, 40 spore mother cells on the male side (PMCs) and 40 on the female side (MMCs) each…
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In a plant, spore mother cells on the male side (PMCs) and on the female side (MMCs) each complete meiosis. Every microspore becomes a functional pollen grain. In each ovule, one megaspore is functional, and a spore mother cell is found in each ovule.
- How many functional microspores are made?
- How many functional megaspores are made?
- How many divisions of single nuclei are needed to make all the embryo sacs from the functional megaspores?
Need a reminder? The key ideaShow
An ovule has one megaspore mother cell (MMC), which is diploid. The MMC divides by meiosis into four haploid megaspores. In most plants, one is functional and three degenerate. The functional megaspore divides by mitosis three times, with no walls, to make 8 nuclei. The mature embryo sac has 7 cells: the egg, 2 synergids, 3 antipodals and the central cell with 2 polar nuclei.
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. PMCs and MMCs.
Plan. Count the useful spores on each side. Then count the divisions for the embryo sacs.
Step 1. The microspores. .
Step 2. The megaspores. One for each MMC, so .
Step 3. The divisions. One embryo sac needs divisions of single nuclei. For sacs: .
Answer: ; ; .
Check. The male side makes four times as many useful spores.
Watch out. Do not count the three degenerate megaspores as useful.
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