By Wilson da Silva
SYDNEY – Crops of wheat, sorghum and peas will suffer serious damage as the atmosphere’s protective ozone layer thins, Australian researchers said on Monday.
Scientists at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) said that after eight days of laboratory exposure to extra doses of ultraviolet-B rays, the three species lost up to 55 per cent of their chlorophyll, a substance essential to plant productivity.
But plants exposed to sunlight boosted their chlorophyll count by a normal rate of 12 per cent.
Ultraviolet-B rays, damaging radiation currently blocked by the ozone layer, will more easily penetrate the atmosphere as ozone thins, the scientists said in a statement.
They also found that rubisco, a protein that allows plants to breathe carbon dioxide, a gas they need to grow, had been “drastically affected in the test plants, where levels were down 28 per cent” compared with normal plants, the scientists said.
The laboratory tests were conducted on rice, cotton, beans, wheat, sorghum and green peas, with the last three plant types showing the most damage. The scientists then conducted in-depth studies of the green peas.
“The two symptoms of ultraviolet-B exposure, the loss of chlorophyll and the rubisco protein in the pea plants, have serious implications for some plant species,” Dr Jan Anderson of the CSIRO’s division of plant industry said in the statement.
Although the rates of ultraviolet-B radiation were much higher than levels likely to arise over the next few decades as a result of ozone depletion, they show that crop production could be severely hampered by even short bursts of ultraviolet-B light.
“Increased ultraviolet-B exposure will stunt growth and deliver lower crop yields,” Anderson said by telephone from Canberra. “Any plant that gets enough ultraviolet-B will die.”
But hope may lie in developing crops more resistant to ultraviolet-B damage. In the tests, increases in the quantity of a colour pigment known as flavonoid, which acts as a sunscreen for plants, were also detected.
Chlorophyll allows a plant to convert sunlight into chemicals useful for its survival in a process known as photosynthesis. Plants also need to breathe carbon dioxide in the process.
Scientists in 1987 first discovered a “hole” in the ozone layer above Antarctica during southern hemisphere summers.
A later study by Australia’s Bureau of Meteorology found that total ozone levels in the area had fallen 10 per cent in the three years to the end of 1989.
Such a fall was described as “staggering” by the bureau’s scientists, who said exisiting climatic models – which seek to predict ozone layer damage – had forecast the region would lose only seven per cent of ozone in the 80 years to 2060.
Man-made chemicals such as chlorofluorocarbons, found in anything from air conditioners to foam packaging, are thought to be a major cause of ozone depletion.
The ozone layer is a thin blanket of gas around the Earth which blocks out damaging radiation. Too much exposure to these rays leads to an increase in skins cancers, eye ailments and immune system-linked diseases, scientists say.