Mira weighs a seedling. On day 0 its fresh weight is 12 g and water makes up 85% of it…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Mira weighs a seedling. On day its fresh weight is and water makes up of it. On day its fresh weight is and water makes up of it.
- What is its dry weight on day ?
- What is its dry weight on day ?
- By how much did the fresh weight rise?
- Has the seedling grown? Explain.
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. Day 0. The part that is not water is . Dry weight .
Step 2. Day 3. The part that is not water is . Dry weight .
Step 3. Fresh weight. It rose from to , so it rose by .
Step 4. Has it grown? The dry weight has not changed. The extra is water. So there is no real growth in this time, even though the fresh weight rose.
Answer: ; ; ; no, only the water content rose.
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