Sort each of these factors as intrinsic (intracellular), intrinsic (intercellular) or extrinsic…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Sort each of these factors as intrinsic (intracellular), intrinsic (intercellular) or extrinsic, and say which of them acts on development.
- A gene in the nucleus that switches on the making of lignin in a young xylem cell.
- A growth regulator that is made in a shoot tip and travels to a lateral bud.
- The length of the day.
- A seedling that is grown in the dark is long and pale. Name the factor that caused this, and say whether it is inside or outside the plant.
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. (a) A gene inside a cell: intrinsic, intracellular.
Step 2. (b) A chemical that moves between cells: intrinsic, intercellular.
Step 3. (c) Day length comes from the surroundings: extrinsic.
Step 4. (d) The factor is light, which is extrinsic. All four factors act on development.
Answer: (a) intrinsic, intracellular; (b) intrinsic, intercellular; (c) extrinsic; (d) light, extrinsic.
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