Exercise 2.8
Observe the slide under a microscope.
Not cross-checked
NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.
Yes, the squashed and stained root tip shows the cells clearly — and they are not all alike.
Aceto-carmine stains the genetic material, so in some cells you see an ordinary nucleus, in others darkly stained thread-like or rod-shaped bodies instead, and in a few the stained material appears drawn towards opposite ends of the cell.
Why they differ: the cells at a growing root tip divide continuously, so at the moment the root was fixed in aceto-alcohol every cell had been caught at a different point in cell division. The slide is a set of snapshots of different stages, which is exactly what Fig. $\displaystyle 2.17$ shows.
Which stage comes first cannot be settled from this chapter — it names neither the stages nor their order, and says the stages of cell division are taken up in higher grades. All that can be said here is that the differences are stages of one continuous process, not different kinds of cell.
