with conifers Sparrow (21)
observed that doses as low as 3 r
and 4 r per day caused death of Pinus rigida after six years
of exposure
(total cumulative dose,
about 8000 r).
Many
plants, however, were dead or dying at doses much below this
cumulated dose, and some visible damage was observed at doses
below 3 r per day.
Observations made in February 1956 in the Marshall
Islands by Fosberg (9,10) also suggest possible radiation
damage to plants twenty-three months after an incidence of
high level radioactive fallout.
the land plants
He found severe damage in
(Guettarda speciosa,
maritima and others)
at Gegen Island,
Cocos nucifera,
Suriana
Rongelap Atoll, where
the "total radiation dose to infinity" was reported to be
3360 r.
lower,
species
Where the levels of radiation were 10 to 100 times
little or no damage was observed.
(Guettarda,
Lepturus repens,
However,
some
and Fleurya ruderalis)
appeared to be normal at Kabelle Island where the radiation
level was high
(total dose 1824 r).
Other species
(Suriana,
Cordia subcordata, Cocos nucifera and Pisonia grandis) were
abnormal in appearance at islands where the levels of radioactivity were lower.
Fosberg suggested that some species of
plants were more susceptible to radiation than others.