-37-
account also for the similarity in the
activity of these tissues
to
decline of radio-
that of the soil.
After the
first 100 days, the rate of decline of radioactivity in all
these tissues was slower than that expected by physical decay of mixed fission products,
indicating that longer-lived
radioisotopes had been taken up by these plants.
The rate of decline of some tissues, however, was different from that of the soil,
suggesting that
some of
the
radioisotopes had been taken up by the plants and distributed
selectively in the plant tissues.
The rapid rate of
of radioactivity in the adventitious leaves,
fruits
decline
flowers,
and
of Scaevola and Messerschmidia indicates the presence
of short-lived radioisotopes in these tissues.
However,
the
rapid rate of decline of radioactivity in the scorched leaves,
which were incapable of normal metabolic activity,
attributed to a selection process.
This
apparent
cannot be
anomaly
might be explained on the basis of the differential adsorption
of fallout particles to the
surfaces of living
versus
dead
tissues, on the differences in the foliar absorption of radio- dgotopes,
and on the different rates of removal of radioiso-
topes by rain water.
The results of the radiochemical analyses of the samples
sollected during the period of February 1955 to October 1955