A farmer grows castor, which is monoecious, and papaya, which is dioecious…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A farmer grows castor, which is monoecious, and papaya, which is dioecious. He wants to know which kinds of pollination can happen in each crop.
- Can autogamy happen in castor? Can geitonogamy happen?
- Can autogamy happen in papaya? Can geitonogamy happen?
- Can xenogamy happen in both crops?
- Which crop is better at avoiding inbreeding?
Need a reminder? The key ideaShow
Outbreeding devices are different timing, different positions, self-incompatibility and unisexual flowers. A pollen tube grows through the style, enters the ovule by the micropyle and enters a synergid. Each tube delivers two male gametes. Time is the distance divided by the rate.
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. Castor has male and female flowers on the same plant. Papaya has them on different plants.
Plan. Use the place of the flowers to decide the kinds that are possible.
Step 1. Castor. The flowers are unisexual, so there is no autogamy. Pollen can go from a male flower to a female flower of the same plant, so geitonogamy is possible.
Step 2. Papaya. There is no autogamy. There is no geitonogamy either, since each plant has one kind of flower.
Step 3. Xenogamy. It is possible in both crops, as long as there are plants of the other kind.
Step 4. The comparison. Papaya avoids inbreeding better, because it prevents both autogamy and geitonogamy.
Answer: (a) no, yes; (b) no, no; (c) yes; (d) papaya.
Watch out. A monoecious plant stops autogamy, but it does not stop geitonogamy.
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