DICLOFOP-METHYL AND DICLOFOP UPTAKE IN OAT (Avena sativa L.) PROTOPLASTS

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Abstract
An isolated oat (Avena sativa L.) protoplast system was used to investigate the uptake of the herbicide diclofop-methyl. Membrane permeability was not adversely affected by the herbicide levels and experimental conditions reported in this study. Neither diclofop-methyl nor diclofop adversely affected membrane permeability of the protoplasts at herbicide concentrations up to 50 μM and 100 μM, respectively. Diclofop-methyl was rapidly taken up by oat protoplasts to a constant level which did not change significantly with incubation times up to 1 h. Forty percent of the added 14C-diclofop-methyl was taken up within 5 s, while diclofop uptake was only 4% over the same time period. Diclofop-methyl uptake was linear with herbicide concentration in the uptake solution up to 50 μM. There was no significant difference between diclofop-methyl uptake by burst or intact protoplast preparations. Rapid diclofop-methyl uptake by oat protoplasts is apparently not a carrier-mediated process. Diclofop was taken up at very low rates under similar experimental conditions. These differences may reflect differences in the phytotoxic activity of the two chemical forms.Key words: Oat, protoplasts, diclofop-methyl uptake