Lesson 2 of 13 · 6 min
Measuring growth
NCERT §13.1.2
Kavya wants to prove her new rice variety grows faster. Should she weigh it, measure it or count its cells?
The lesson in notes
In short
At the cellular level growth is mainly an increase in the amount of protoplasm. Protoplasm is hard to measure directly, so a quantity roughly proportional to it is measured instead.
Parameters used: increase in fresh weight, dry weight, length, area, volume and cell number.
A single maize root apical meristem can produce more than 17,500 new cells per hour. Here growth shows up as an increase in cell number.
Cells in a watermelon may increase in size up to 3,50,000 times. Here growth shows up as an increase in cell size.
The right parameter depends on the organ: a pollen tube's growth is measured as length, a dorsiventral leaf's as surface area.