Fig.
6.8-4b. Magnification of a root apex of corn. The boundary between
the root proper and root cap is distinct. An important aspect of zonation is not
visible in any histological preparation like this -- much of the root apical
meristem that is visible here is mitotically quiescent -- the quiescent
center can only be revealed by supplying the root with radioactive
thymidine and checking to see if the nuclei are synthesizing DNA (if they are,
the nuclei will become radioactive; if the nuclei are not preparing for mitosis,
the nuclei will not become radioactive).