-29-
different rates.
In Scaevola the rate of decline of the
basal and terminal leaves was rapid (t72-2)
post Nectar,
for about 50 days
then when the pre-Nectar level was reached,
was much slower
(470-4)
for the remainder of the study.
it
The
decline of radioactivity of the terminal leaves is shown in
Figure 9.
In the flowers,
scorched leaves,
adventitious shoot leaves,
the rate of decline was rapid
the entire period (for flowers see Figure 10).
and
(t72 +0)
for
The differ-
ences in the rates of decline of radioactivity of these tissues may be due to the fact that the terminal leaves were
protected by older leaves and were not exposed to fallout to
the same degree as the flowers and scorched leaves.
This
difference in rate of decline may reflect the uptake of longer-
lived fission products by the protected leaves.
In the stems
the rate of decline was less rapid than in other tissues.
Figure ll shows the decline of radioactivity of the entire stem.
In each of these figures the decay of mixed fission products
according to Hunter and Ballou (15)
is included for comparison.
In Messerschmidia therewere also three types of decline,
these tissues having the same type of radioactive decline as
the Scaevola tissues
ever,
the decline was
(Figs.9-11).
the same
In the other species, how~
for each tissue;
in Portulaca, Triumfetta and Boerhaavia,
for example,
the rate of declim fr