Look at four plants. A young cotton plant bears leaves of one shape…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Look at four plants.
- A young cotton plant bears leaves of one shape. The same plant, when mature, bears leaves of another shape.
- A buttercup plant bears thread-like leaves under water and broad leaves in air.
- A young coriander plant bears broad leaves. Higher up, the same plant bears finely cut leaves.
- Name the general term for these cases, and say whether (a), (b) and (c) are caused by the stage of life or by the surroundings.
Need a reminder? The key ideaShow
Differentiation: cells from the meristems mature into permanent cells. Dedifferentiation: living permanent cells begin to divide again, as in the interfascicular cambium and the cork cambium. Redifferentiation: the new cells mature again. Development is growth plus differentiation. Plasticity: heterophylly by age in cotton, coriander and larkspur, and by surroundings in buttercup. Intrinsic factors are genes and growth regulators. Extrinsic factors are light, temperature, water, oxygen and nutrition.
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. The term. A plant that bears leaves of different shapes shows heterophylly. It is an example of plasticity.
Step 2. (a) The leaf shape changes with the age of the plant: the stage of life.
Step 3. (b) The leaf shape changes with water or air: the surroundings.
Step 4. (c) The leaf shape changes as the plant grows older: the stage of life.
Answer: heterophylly (plasticity); (a) stage of life; (b) surroundings; (c) stage of life.
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