-28-
49 of 54 comparisons the scorched leaves contained the
highest levels of radioactivity.
The chi-square test shows
that this difference is highly significant.
Since the
scorched leaves were unable to absorb nutrients by metabolic means they must have accumulated the radioactive
material by physical adsorption.
A similar test showed
that the internal portion of the stem contained the lowest
amounts of beta radioactivity, which is not surprising,
because the internal portion of the stem is the only tissue sampled in which there would be no
nation.
surface contami-
No marked differences in levels of radioactivity
were noted among the other six tissues.
Comparisons of the relative amounts of beta radioactivity among the tissues of plant species collected at
Belle Island (Table 4) showed that the plants with a prostrate growth habit, such as that found in Triumfetta and
Boerhaavia,
grass
and the forms with limited growth,
(Lepturus) and the purslane
such as the
(Portulaca), contained
higher levels of radioactivity than the plants with a taller
growth habit,
such as Scaevola and Messerschmidia.
With increased time after the Nectar test the levels
of radioactivity of the different plant parts declined
at