The plants in the contaminated area have a mechanism to protect future progenies by blocking transfer of radio-nuclides to the seeds

Since April 1986, scientists got a unique opportunity to study the impact of radioactive contamination on the plants and animals living near Chernobyl.

The Chernobyl Forum, which is made up of eight specialized agencies of the UN, in its landmark report titled ‘Chernobyl’s Legacy: Health, Environmental and Socio-Economic Impacts,’ made some general remarks on the impact of the accident on the natural environment.

Details emerging

More detailed results of research are emerging now. Researchers from the Slovak Academy of Sciences reported that plants adapted very well to the contaminated environment (Journal of Proteome Research, 2009).

In 2007, they planted ordinary soybean seeds and flaxseeds at a contaminated field in the restricted area about 5 km from the stricken nuclear power plant and at a control field in the same region nearly 100 km away.

The soil in the contaminated area had 163 times more radioactivity (cesium-137) than that in the control area.

The seeds from the contaminated area had less length and width; they weighed about 50 per cent less than those from the control field. Their water-inhibition process was found to be different.

The uptake of radio-nuclides varied significantly within the plant and also between plants.

Though the plant absorbed about 10 per cent of the radioactive contamination, the seeds showed only very low levels of radioactivity. The plants have a mechanism to protect future progenies by blocking transfer of radio-nuclides to the seeds.

Brazil nut, which is well known as the most radioactive food, accumulates radioisotopes of radium. The root system of that tree covers a large area of soil and accumulates radioactivity from the soil.

Nature does not develop any mechanism to arrest the accumulation of radioactivity by the seed. “How do you explain the difference in behaviour between soy plant and Brazil nut tree?”

“I can only speculate that trees might have different mechanisms than plants. Trees are long-living organisms, when compared to crop plants, and thus might not have immediate interest to protect their future progenies from unfavourable environmental conditions”, Dr Martin Hajduch the lead author responded to my e-mail query.

Increased levels

The researchers wanted to develop a model for plant adaptation to increased levels of radiation. They froze the seeds with liquid nitrogen, crushed them to extract the mixture of proteins they contained and ran the seed proteins on 2-Dimensional gel Electrophoresis.

They looked for differences in expression levels of proteins between seeds grown in the contaminated field versus the control field.

The seeds from soy plants grown in contaminated field contained different types and amounts of proteins compared with those from control field. The former plants made many changes to defend themselves and adjusted the levels of several proteins that guard against heavy metals, disease etc.

The researchers found that a certain specific protein which, in test tube studies demonstrated a protective effect against radiation-induced damage, exhibited a 32 per cent higher expression in the seeds from contaminated fields.

The levels of hundreds of proteins which are known for their ability to shuffle other proteins around or tie them up in storage had been lowered.

Why soybean?

Why did they choose soybean plant for the study? “The reason is that soybean is a very important crop worldwide and I worked with it also before”, Dr Hajduch responded to my e-mail query.

“Large percentage of population depends on soybean”, he added.

Do you expect that the mechanisms you observed will be present in plants growing in high background radiation areas such as certain coastal regions in India?

“I would expect it as the mechanisms that plants use to protect their future progenies from harmful effects of radio-contaminated environment should be the same, regardless of the geographical location”, he replied.

Why should we carry out such studies?

“If scientists can understand how plants survive in ultra-hostile environments, it will help them engineer super hearty plants to withstand drought conditions or grow on marginal cropland”, (Aaron Rowe, wired.com, 2009).

K.S. PARTHASARATHY
FORMER SECRETARY, AERB

ksparth@yahoo.co.uk