EasyBiologyHigh School (9–10)GeneralPlant Biology › Plant Hormones and MovementsHuman Body › Hormones and the Endocrine SystemNumericalBoard Exam
On a lily flower, a pollen grain lands on the stigma…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
On a lily flower, a pollen grain lands on the stigma. Its tube grows down the style at micrometres each minute, and the ovule lies mm below. How many minutes, and about how many hours, does the tube take to reach the ovule? What guides it there?
Need a reminder? The key ideaShow
A tropism is a growth movement towards (positive) or away from (negative) a stimulus. Shoots grow towards light and away from gravity. Roots grow towards gravity and towards water. A pollen tube grows towards a chemical made by the ovule. A part bends when one side grows faster than the other.
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. Distance. micrometres.
Step 2. Time. minutes.
Step 3. In hours. hours.
Step 4. The guide. A chemical from the ovule guides the tube, so this is chemotropism.
Answer: minutes, about hours, guided by a chemical from the ovule.
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