stimulation in mustard48 and in potato disks during light stimulation.” Here one may refer
to the phenomenon as a de novo synthesis of enzyme. It may be misleading, however, to refer
to an induction of the enzyme until certain other facts are established. There, is evidence,
based on cycloheximide treatments, that an inactivator of PAL is present in a number of
plants such as potato,4g mustard50 and radish.51 In Xanthium the ‘induction’ of PAL was
found to be due to a decreased rate of inactivation of the PAL molecule.52*53 Apparently, in
this system there is a continuous production of inactivator and changes in PAL levels are a
reflection of a change in rate of synthesis of the inactivator and not of an increased rate of
synthesis of PAL.