November 7, 2012
Soybean plants at Chernobyl produce fertile seeds
The environmental impact of radiation at Chernobyl continues to interest many researchers. There are only very limited studies on plants. Chernobyl accident led to contamination of large tracts of land.
“There have been a few molecular analyses of plants grown in the radio-contaminated Chernobyl area, and there is as yet no broad understanding of the mechanisms that underlie survival,” Dr. Katarı´na Klubicova and coworkers from the Slovak Academy of Sciences, Slovakia reported in the October 2012 issue of PLoS ONE, an open access journal.
Researchers found that in spite of the magnitude of the Chernobyl nuclear accident, local flora continues to grow and reproduce in the radioactively contaminated soil.
“Although there has been more than 80 years of research addressing the effects of ionizing radiation on plants, the ongoing success of plants in the Chernobyl area was not anticipated,” the researchers added.
These researchers who have been pioneers in the field, analyzed protein abundance in mature seeds harvested from first generation soybean plants grown in radioactive and non-radioactive plots in the Chernobyl area . They reported that the plants adapted very well to the contaminated environment (Journal of Proteome Research, 2009).This study was described in The Hindu on July 23, 2009.
There was evidence suggesting that the plant adapts itself to heavy metal stress and protects itself against radiation damage. Plants mobilise seed storage proteins to adjust to increased levels of ionising radiation.
Researchers planted soybean plants since 2007 in a radioactive field located 5 km from the Chernobyl Nuclear Power Plant (CNPP), near the village Chystogalivka, and in a control field established directly in a non-radioactive area in the town of Chernobyl. The soil in the radioactive field contained 20,650 Bq /kg of Cs-137 and 5180 Bq/ kg of Sr-90 and in the non-radioactive field 1414 Bq/ kg of Cs-137 and 550 Bq/ kg of Sr-90.( In a Bq of radioactivity one disintegration occurs every second).
The dry weight of mature soybeans harvested from the radioactive Chernobyl area was only 63 per cent of those harvested from the non-radioactive area.
Total oil content in mature dry seeds harvested from the radioactive area decreased to 20 per cent from 25 per cent in the seeds harvested from the non-radioactive area.
Soybeans from the radioactive Chernobyl area were smaller, contained less oil, and were fertile. The Abundances for 211 proteins were characterised during soybean seed development in non-radioactive and radioactive Chernobyl areas.
“…. the study showed that biochemistry of soybean seed development in radio-contaminated Chernobyl area is altered the specific way that resulted into the smaller seeds with less oil … ”, Dr Martin Hajduch, co-author and Senior Scientist, Slovak Academy of Sciences responded to an e-mail query.
The researchers observed that relatively larger amounts of Sr-90 got transferred from soil to plant compared with Cs-137.
“This is due to different biochemical properties of these two radio-nuclides that are still not well understood,” he added.
“In the case of both contaminated and control fields, Sr-90 got concentrated in the shoot system for both control and contaminated (550 Bq/kg to 1720Bq/kg (3 times) for control;5180Bq/kg to54,000 Bq/kg (9.5times) for contaminated. How do you explain this?”
Dr Hajduch thus responded to the query:
“The biochemical pathways of radio-nuclides within the plants are still not well understood. Different levels of Sr-90 and Cs-137 accumulation in soybean are due to different biochemical properties of these radio-nuclides.”
“Will the energy absorbed from Sr-90 by the seeds during their storage dramatically affected its behaviour during its growth during the second generation?”
“There was probably some minor effect of accumulated radioactivity on the seeds during the storage. However the effect was not big, because mature seeds are not biologically active tissue. This is also documented by the fact that seeds were able to germinate,” he clarified.
Scientists measured Cs-137 and Sr-90 in the shoot system (entire plant without roots and seed pods) and in the seeds. They found that the shoot system accumulated more radioactivity than seeds. This may be nature’s scheme to resist further damage by limiting accumulation of radioactivity in seeds.
In an interesting study published in PLoS ONE Journal in 2009, Dr Sher Ali and his co-workers from the National Institute of Immunology, Delhi showed some evidence that while natural background radiation may be responsible for varying alterations, it leaves the DNA of the vital germ line intact. Nature’s inexplicable schemes save all living things from extinction.