A munber of studies of the uptake of Sx~90 have been undertaken
with a variety of Meld crops.
Considerable variation oceura from one
species to another.
The cesiun ion is so firmly held by the acil surfaces that it is
not readily available to plants.
Likewlee, the rare earths and plutoni-
wa are little taken up by plants frou soila, hence, these elements
beceme of interest only to the extent that they are deposited directly
on foodstuffs or in water supplies.
All evidence avaliable paints to
a rather large discrimination factor for the uptake of cesiwa from soil.
Henzel and Heald found a factor of 50 in favor of the uptake of potasREE
sium relative to cesiwa.
Syidence for discrimination against the uptake
of strontiwa relative to calolua is conflicting.
Under field condltions
at 93 sites in 11 states no discrimination, on the average, was found
between the ratio of calcium and strontium in alfalfa arxi wheat and the
ratio in the exchangeable form in the solis on which they were growm.
As Alexander has said, there say be no single answer to the question
but 1t seeme that one showld not count on a large discrimination factor
against strontium.
*. =. . At the present time in the United States, we
ean find forage that has Sr-90 te calcium ratios that are lower than,
higher than,or equal to the ratio of these elements in an exchangeable
fora in the surface horisons of the soils from which the forage cane."
These variations are probably due to unequal distribution ef the fission
saint