Abstract
Experiments were carried out with autoradiographic and counting techniques to determine if differential absorption was a factor influencing the selective toxicity of the foliar-applied herbicides, 4-chloro-2 methylphenoxyacetic acid (MCPA) and 4-(4-chloro-2-methylphenoxy) butyric acid (MCPB). Treatment of fat hen (Chenopodium album) which is susceptible to both herbicides and black bindweed (Polygonum convolvulus) which is resistant to both, showed that MCPA and MCPB were extensively translocated in the susceptible species; both, however, remained localized in the treated leaves of the resistant black bindweed. Further experiments using broad bean (Vicia faba) which was susceptible to MCPA and resistant to equivalent doses of MCPB showed that considerably more MCPA was translocated throughout the treated plants. Leaf flotation experiments suggested that differential penetration of bean leaf cuticle, may in part at least, explain this difference in toxicity. Greater uptake of MCPA after 6- and 8-h treatment periods was recorded and penetration of both herbicides was generally more rapid through the abaxial surface, reflecting the presence of stomata and the thinner cuticle of the under-surface. Further evidence of the action of cuticle as a selective barrier to herbicide penetration was obtained using cuticle isolated from tomato fruits and onion scale leaves. These results are to be
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Kirkwood, R. C.;
Robertson, M. M.;
Smith, J. E.
[1]
- University of Strathclyde, Glasgow (United Kingdom)
Citation Formats
Kirkwood, R. C., Robertson, M. M., and Smith, J. E.
Differential Absorption as a Factor Influencing the Selective Toxicity of MCPA and MCPB.
IAEA: N. p.,
1966.
Web.
Kirkwood, R. C., Robertson, M. M., & Smith, J. E.
Differential Absorption as a Factor Influencing the Selective Toxicity of MCPA and MCPB.
IAEA.
Kirkwood, R. C., Robertson, M. M., and Smith, J. E.
1966.
"Differential Absorption as a Factor Influencing the Selective Toxicity of MCPA and MCPB."
IAEA.
@misc{etde_22118932,
title = {Differential Absorption as a Factor Influencing the Selective Toxicity of MCPA and MCPB}
author = {Kirkwood, R. C., Robertson, M. M., and Smith, J. E.}
abstractNote = {Experiments were carried out with autoradiographic and counting techniques to determine if differential absorption was a factor influencing the selective toxicity of the foliar-applied herbicides, 4-chloro-2 methylphenoxyacetic acid (MCPA) and 4-(4-chloro-2-methylphenoxy) butyric acid (MCPB). Treatment of fat hen (Chenopodium album) which is susceptible to both herbicides and black bindweed (Polygonum convolvulus) which is resistant to both, showed that MCPA and MCPB were extensively translocated in the susceptible species; both, however, remained localized in the treated leaves of the resistant black bindweed. Further experiments using broad bean (Vicia faba) which was susceptible to MCPA and resistant to equivalent doses of MCPB showed that considerably more MCPA was translocated throughout the treated plants. Leaf flotation experiments suggested that differential penetration of bean leaf cuticle, may in part at least, explain this difference in toxicity. Greater uptake of MCPA after 6- and 8-h treatment periods was recorded and penetration of both herbicides was generally more rapid through the abaxial surface, reflecting the presence of stomata and the thinner cuticle of the under-surface. Further evidence of the action of cuticle as a selective barrier to herbicide penetration was obtained using cuticle isolated from tomato fruits and onion scale leaves. These results are to be confirmed using bean leaf cuticles. Whilst in the higher plants MCPA is more toxic than MCPB, previous work has shown that MCPB is a more effective inhibitor of lower organisms such as bacteria, fungi and algae. Treatment of mycelial discs of Aspergillus niger showed that absorption of MCPB was more rapid than MCPA, though the differential tended to diminish during the 20-h treatment period. Respiratory inhibition closely followed the uptake pattern. Repeated experiments using mitochondria isolated from A.niger mycelium have demonstrated that greater uptake of MCPB coincided with an enhanced inhibitory effect of this herbicide. In addition it was found that mitochondria extracted from this mycelium of A. niger grown in a nutrient-herbicide medium showed a greater absorption of MCPB than MCPA. These results have great significance since it has been shown that the mitochondria are the probable site of toxic action of these compounds in A. niger. It was tentatively concluded from these early experiments that differential absorption was a factor influencing toxicity of these two herbicides, but that this would be additional to the selectivity resulting from the widely accepted {beta} -oxidizing enzyme system. (author)}
place = {IAEA}
year = {1966}
month = {May}
}
title = {Differential Absorption as a Factor Influencing the Selective Toxicity of MCPA and MCPB}
author = {Kirkwood, R. C., Robertson, M. M., and Smith, J. E.}
abstractNote = {Experiments were carried out with autoradiographic and counting techniques to determine if differential absorption was a factor influencing the selective toxicity of the foliar-applied herbicides, 4-chloro-2 methylphenoxyacetic acid (MCPA) and 4-(4-chloro-2-methylphenoxy) butyric acid (MCPB). Treatment of fat hen (Chenopodium album) which is susceptible to both herbicides and black bindweed (Polygonum convolvulus) which is resistant to both, showed that MCPA and MCPB were extensively translocated in the susceptible species; both, however, remained localized in the treated leaves of the resistant black bindweed. Further experiments using broad bean (Vicia faba) which was susceptible to MCPA and resistant to equivalent doses of MCPB showed that considerably more MCPA was translocated throughout the treated plants. Leaf flotation experiments suggested that differential penetration of bean leaf cuticle, may in part at least, explain this difference in toxicity. Greater uptake of MCPA after 6- and 8-h treatment periods was recorded and penetration of both herbicides was generally more rapid through the abaxial surface, reflecting the presence of stomata and the thinner cuticle of the under-surface. Further evidence of the action of cuticle as a selective barrier to herbicide penetration was obtained using cuticle isolated from tomato fruits and onion scale leaves. These results are to be confirmed using bean leaf cuticles. Whilst in the higher plants MCPA is more toxic than MCPB, previous work has shown that MCPB is a more effective inhibitor of lower organisms such as bacteria, fungi and algae. Treatment of mycelial discs of Aspergillus niger showed that absorption of MCPB was more rapid than MCPA, though the differential tended to diminish during the 20-h treatment period. Respiratory inhibition closely followed the uptake pattern. Repeated experiments using mitochondria isolated from A.niger mycelium have demonstrated that greater uptake of MCPB coincided with an enhanced inhibitory effect of this herbicide. In addition it was found that mitochondria extracted from this mycelium of A. niger grown in a nutrient-herbicide medium showed a greater absorption of MCPB than MCPA. These results have great significance since it has been shown that the mitochondria are the probable site of toxic action of these compounds in A. niger. It was tentatively concluded from these early experiments that differential absorption was a factor influencing toxicity of these two herbicides, but that this would be additional to the selectivity resulting from the widely accepted {beta} -oxidizing enzyme system. (author)}
place = {IAEA}
year = {1966}
month = {May}
}