Two students argue about the pollen grain…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Two students argue about the pollen grain. Asha says that it is a male gamete, because it is haploid and carries the male genes. Ben says that it is a male gametophyte.
- Who is right?
- Give two reasons from the origin and from the contents of the grain.
- Name the structures in a three-celled grain that are the actual male gametes.
Need a reminder? The key ideaShow
A pollen grain is the male gametophyte. Its exine is made of sporopollenin and has germ pores. Its intine is made of cellulose and pectin. A grain is about to micrometres wide, and mm is micrometres.
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. Asha says gamete. Ben says gametophyte.
Plan. Compare the grain with the definition of a gametophyte.
Step 1. The origin. The grain grows from a microspore, which was made by meiosis. It is therefore a spore, and a spore grows into a gametophyte.
Step 2. The contents. The grain has two or three cells. It makes gametes by mitosis. A structure that makes gametes is a gametophyte, not a gamete.
Step 3. The gametes. The two cells formed from the generative cell are the male gametes.
Answer: Ben is right. The pollen grain is the male gametophyte. The male gametes are the two cells formed from the generative cell.
Watch out. Asha is right that the grain is haploid, but a haploid structure is not always a gamete.
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