New research shows some plants may be better able to rid themselves of pesticide residue than others.
In 2006, Jing Quan Yu, with the Department of Horticulture at Zhejiang University in China, and his colleagues, began research to determine a method of reducing the amount of pesticide residues in crops.
“Initially, we wanted to study whether (brassinosteroids) can alleviate the pesticide toxicity to crops, because reductions in crop yields due to heavy use of pesticide are often observed in China,” said Yu in an e-mail exchange from Hangzhou, China.
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Brassinosteriods (BRs) are a group of steroidal plant hormones known to protect crops from the toxicity of pesticides, herbicides and insecticides.
Yu and his colleagues tested the effects of BRs, particularly 24 epibrassinolides (EBRs), on plants that had been exposed to pesticides.
They found that introducing external BRs could alleviate the negative effects of pesticides on photosynthesis and help the plants better metabolize the pesticides.
“This suggests that tolerant plants have a higher capacity to remove pesticide residue,” Yu said.
The research found that EBRs were able to reduce pesticide residues by 30 to 70 percent, depending on the experiment condition and plant species.
The group tested cucumbers, Chinese cabbage, tomatoes and tea. They tested the plants using the pesticides chlorpyrifos, B-cypermethrin, chlorothalonil and carbendazim.
“Interestingly, BRs can promote plant metabolic activity toward all these fungicides and insecticides … however, the mechanism may be different,” said Yu.
He explained the different mechanisms are probably due to the difference in absorption and responsiveness to BRs in the plants.
The EBR reduced the toxicity of the pesticide, accelerated its dissipation, increased the activities of detoxification enzymes and induced the production of detoxification proteins.
“We are very excited by this outcome because it would be great to use this mechanism to reduce pesticide residues in agricultural products,” Yu said. “There are no available and practical ways to reduce the pesticides in plants until now.”
Yu said it is important to reduce pesticide residues in agricultural products because of the negative effects the residues can have on plants and humans.
In plants, pesticide residues can inhibit photosynthesis, reduce growth and affect the plant’s secondary metabolism.
For humans, accidental and short-term exposure to high doses of pesticides can cause acute poisoning through the inhibition of the enzyme cholinesterases.
Long-term exposure to low doses can cause chronic toxicity, such as cancer, teratogenesis and reproductive toxicity.
The results of the study were published in the Sept. 23, 2009 issue of the American Chemical Society’s Journal of Agricultural and Food Chemistry.
