A farmer grows two varieties of bean in a dry season…
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 two varieties of bean in a dry season. Variety A is normal. Variety B makes very little abscisic acid. In the dry weather B wilts, while A stays fresh.
- Why does B lose water faster?
- What would a spray of ABA do to the leaves of B?
- In the next season some seeds of B begin to germinate while still in the pod on the plant. Which property of ABA is missing here?
Need a reminder? The key ideaShow
Ethylene is a gas that ripens fruit, causes the respiratory climacteric, and promotes senescence and abscission. Ethephon releases it. Abscisic acid is the stress hormone: it closes stomata, keeps seeds dormant and opposes gibberellins.
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.
Step 1. (a) ABA closes the stomata in a drought. B has little ABA, so its stomata stay open and water escapes.
Step 2. (b) A spray of ABA would close the stomata of B and cut the water loss.
Step 3. (c) ABA keeps a developing seed dormant and stops germination. Without enough ABA, seeds germinate in the pod.
Answer: (a) open stomata; (b) the stomata close; (c) the role of ABA in seed dormancy.
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