By Wilson da Silva
SYDNEY – Scientific tests have proved a link between stunted plant growth and higher ultraviolet radiation caused by the depletion of the Earth’s protective ozone layer, the leader of an Australian research team says.
At Australian National University, soybean, rice and pea crops were given repeated but low-level bursts of ultraviolet-B (UV-B) light, damaging radiation which is mostly screened out by the ozone layer.
“Every one of them had some level of reduction in performance, and some declines were as much as 70 per cent,” said botanist Malcolm Whitecross.
Whitecross, who leads a research group at the university’s division of botany, said the findings have serious implications for plant productivity.
“What we’re seeing is damage to the productive apparatus of the plants,” he said. “I don’t think there’s any doubt ... it is damage at the molecular level.”
The crops were irradiated for six to eight weeks with five to 10 per cent more UV-B than normal. All of six indicators, such as chlorophyll and oxygen production, showed performance falls of 20 to 25 per cent. Peas suffered declines of 50 per cent, and as much as 70 per cent for some strains.
Whitecross called the UV-B doses his group applied conservative, estimating that in reality some 20 per cent more UV-B gets through during peak times.
Four commercial strains of soybean and two of rice were tested. Some varieties of the same plant withstood UV-B better than others, suggesting a natural resistance which scientists may in future be able to genetically transfer from hardy to weaker varieties.
Whitecross plans to expand the research into 20 varieties of rice in September and later into soybeans. “None of the plants finds even a small increase in UV-B beneficial,” Whitecross said.
“It’s an energy overload which is obviously turned into heat which destroys proteins (important for plant production).”
The ozone layer is a thin gas sheet around the Earth which scientists say is being steadily depleted by man-made chemicals, especially CFCs (chlorofluorocarbons), chemicals found in products such as air conditioners and foam packaging.