The apical meristem of a maize root makes more than 17,500 new cells in one hour…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
The apical meristem of a maize root makes more than new cells in one hour. Take it as exactly cells an hour.
- How many cells does it make in hours?
- How many cells does it make in one minute?
- After they are made, these cells move away from the tip. Name the phase of growth that most of them pass through next, and say what changes in the cell.
- Which measure of growth would you use for this root apex: weight, length or cell number?
Need a reminder? The key ideaShow
Growth is a permanent, irreversible increase in size, made by living cells using energy. Plant growth is open, because meristems keep adding cells. In a root the cells pass through three phases, from the tip: meristematic (small, dividing, large nucleus), elongation (vacuoles grow, cells enlarge, new wall) and maturation (full size, thick wall). Dry weight is a better measure than fresh weight, because the water content changes.
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. Eight hours. cells.
Step 2. One minute. cells. A fresh cell appears about every fifth of a second.
Step 3. The next phase. The new cells leave the meristem and enter the elongation phase. Their vacuoles grow, the cells enlarge and new wall is laid down.
Step 4. The measure. The apex is a place where cells are made in huge numbers, so cell number is the best measure.
Answer: cells; cells; the elongation phase; cell number.
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