1022-7954/05/4109- © 2005 Pleiades Publishing, Inc.
Russian Journal of Genetics, Vol. 41, No. 9, 2005, pp. 1021–1027. Translated from Genetika, Vol. 41, No. 9, 2005, pp. 1244–1250.
Original Russian Text Copyright © 2005 by Abramov, Rubanovich, Shevchenko.
It is difﬁcult to estimate the total irradiation dose per
generation in plants growing in contaminated regions,
because seeds of wild plants do not germinate simulta-
neously in soil: some seeds rest, accumulating the irra-
diation dose, to germinate in the following years. For
the same reason, the generation under study cannot be
established unequivocally. The irradiation dose can be
determined for seeds collected in contaminated
regions. The total dose of chronic irradiation in seeds
developing in the ﬁeld is a product of the dose rate and
the time it takes for a zygote to develop into a mature
seed. This time is one month on average in the case of
As estimated with sufﬁcient accuracy, one or two
initial cells giving origin to the reproductive organs are
contained in an
seed, depending on the
growth conditions [1, 2]. Each pod is formed by the
progeny of one initial cell. As a result, M
from irradiated seeds are usually chimeric for newly
arising mutations, since one locus is unlikely to be
affected by mutations in both initial cells. This is espe-
cially true for the doses considered in this work, from
0.2 cGy to 20 Gy.
Note that M
chimeras for newly arising mutations
do not result only from irradiation of seeds.
 have observed that chimeric
plants are already generated when
are exposed to acute irradiation 12 h after pollination;
i.e., their chimeric character develops from the ﬁrst
division of the apical cell. All mutant plants had the
mutant sector of approximately 50% regardless of the
period between pollination and induction of mutations,
suggesting the involvement of two initial cells.
Thus, the presence of at least two initial cells of the
reproductive meristem in
makes it possible
to differentiate the mutation load arising in the given
generation (the proportion of chimeric plants) from the
load accumulated earlier (the frequency of complete
heterozygotes for lethals).
To summarize, it is possible to estimate the fre-
quency of mutations induced in a particular generation
and to calculate the ionizing radiation dose that is
responsible for the effect of chronic irradiation of this
generation. Examination of several regions with a gra-
dient of radioactive contamination makes it possible to
construct a dose dependence of chronic irradiation of
for every year.
MATERIALS AND METHODS
The genetic effects of low-dose irradiation were
studied in plants that were grown in a greenhouse from
seeds developed under conditions of chronic irradia-
tion, at experimental sites located within the 30-km
control region of the Chernobyl Atomic Power Plant.
Frequencies of recessive embryonic lethals and chloro-
phyll mutations were estimated by Muller’s embryo test
. This test reports simultaneously three quantitative
characteristics of the mutation process in
plants heterozygous for embryonic
of pods containing mutant
embryos on M
plants, and frequency
embryos in M
is considered in this paper.
Four or ﬁve successive pods from one inﬂorescence
were analyzed in each plant.
irradiation were calculated from the air
exposure dose rate, which was measured on the soil sur-
Genetic Effects of Low-Dose Chronic Irradiation
of Developing Seeds of
V. I. Abramov, A. V. Rubanovich, and V. A. Shevchenko
Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 117809 Russia;
fax: (095)132-89-62; e-mail: email@example.com
Received January 14, 2005
—A six-year study, starting in 1987, was focused on the frequency of embryonic lethals and chloro-
phyll mutations that arose in developing seeds of
growing at sites varying in the level of
radioactive contamination in the 30-km control region of the Chernobyl Atomic Power Plant. The dose rate of
chronic irradiation varied from 200
R/h to 2.4 R/h. To study the genetic effects of various levels of radioactive
contamination, the frequency of mutations arising in a particular generation was determined and the irradiation
dose was estimated for the given generation. The dose dependence of the mutation frequency proved to follow
a power function with a power less than unity, suggesting a relatively high effect for low-dose irradiation. Pos-
sible explanations of this phenomenon are discussed.