Bentazon sensitivity

Figure 3. Relative sensitivity of a rabbit antibody to bentazon and methylated bentazon. A rabbit antisera against an N-derivatized bentazon had better recognition of methylated bentazon than bentazon. Coating antigens were Bz(6)-O-MPAA-BSA and Bz-succ-BSA for methyl bentazon and bentazon respectively. These curves indicate that one may find a much more sensitive assay for a derivative than for the parent compound. As in chromatographic analysis, it may be advantageous to run...

Immunoassays offer much potential for rapid screening and quantitative analysis of pesticides in food and environmental samples. However, despite this potential, the field is still dominated by conventional analytical approaches based upon chromatographic and spectrometric methods. We examine some technical barriers to more widespread adoption and utilization of immunoassays, including method development time, amount of information delivered and inexplicable sources of error. Examples are provided for paraquat in relation to exposure assessment in farmworkers and food residue analyses molinate in relation to low-level detection in surface waters and bentazon in relation to specificity and sensitivity requirements built in to the immunizing antigen. A comparison of enzyme-linked immunosorbent assay (ELISA) results with those obtained from conventional methods will illustrate technical implementation barriers and suggest ways to overcome them. 

The primary mode of action of bentazon is the inhibition of photosynthetic CO2-fixation by the plants (Mine and Matsunaka, 1973, 1975). A marked inhibition of C02-fixation develops rapidly both in resistant rice and in sensitive Cyperus serotinus after treatment with bentazon, but while tolerant rice recovers almost completely in 5 days, sensitive Cyperus serotinus does not recover. 

Searching into the cause of the selectivity of bentazon. Mine et al. (1973, 1975) investigated the adsorption and translocation of the herbicide in sensitive Cyperus serotinus and in resistant rice. There is no substantial difference in either the absorption or in the translocation of the herbicide in the two kinds of plants. However, in rice 80% of the bentazon absorbed is metabolised in 24 hours and 85% is converted in 7 days to a water-soluble metabolite. The major metabolite formed in rice is 6-isopropyl-2,l,3-benzothiadiazinon-(4)-2,2-dioxide O- -glucopyra-noside. Only 5% of unchanged bentazon can be detected in rice, while in Cyperus serotinus 50-75% of the bentazon is present in unchanged form after 7 days. 

Similarly, a large quantity of water-soluble metabolite is formed in resistant soybean, barnyard grass (Echinocloa crus galli) and in rice thus, the cause of selectivity is the different measure to which sensitive and tolerant plants are able to metabolise, and hence detoxicate, bentazon. 

Triazine herbicides and quinoclamine, having the mode of action in inhibition of PS II (Photosynthesis at photosystem II) had low variability on sensitivities in different algal taxa. On tiie other hand. Amide herbicide such as Pretilachlor and Cafenstrole as well as sulfonylurea herbicides of bensulfiironmethyl and imazosulfuron had great variability on sensitivities in different algal taxa. These herbicide have in other the mode of action in inhibition of cell division or in inhibition of acetolactate synthase rather tiian in inhibition of PS II. Carbamate herbicide showed relatively low toxicity on algae. Daimuron and bentazone exhibit low toxicity on all tire tested species (Figure 3). 

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