rimsulfuron uptake, translocation, metabolism and

<span style="font-size: small; font-family: TimesNewRomanPSMT;"><span style="font-size: small; font-family: TimesNewRomanPSMT;"><p align="left">Research was conducted to determine the role in selectivity</p><p align="left">of uptake, translocation, metabolism and ALS (acetolactate</p><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left">synthase) activity of rimsulfuron in two maize (</p></span></span></span></span><p align="left"><em><span style="font-size: small; font-family: TimesNewRomanPS-ItalicMT;"><span style="font-size: small; font-family: TimesNewRomanPS-ItalicMT;">Zea mays</span></span></em><span style="font-size: small; font-family: TimesNewRomanPSMT;"><span style="font-size: small; font-family: TimesNewRomanPSMT;"><p align="left">L.) hybrids (‘Cargill 2127’, tolerant, and ‘Pioneer 3897’,</p><p align="left">sensitive) grown at temperatures of 14°C and 21°C. Forty</p><p align="left">eight hours after treatment (HAT), uptake of rimsulfuron</p><p align="left">was 40% and 67% in ‘Pioneer 3897’, and 26% and 43%</p><p align="left">in ‘Cargill 2127’ at 14°C and 21°C, respectively. Neither</p><p align="left">total translocation nor allocation of rimsulfuron in various</p><p align="left">organs differed greatly between the hybrids. Translocation</p><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left">of</p></span></span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left"> </p></span></span></p><p align="left"><span style="font-size: xx-small; font-family: TimesNewRomanPSMT;"><span style="font-size: xx-small; font-family: TimesNewRomanPSMT;">14</span></span><span style="font-size: small; font-family: TimesNewRomanPSMT;"><span style="font-size: small; font-family: TimesNewRomanPSMT;">C-rimsulfuron was greater at 21°C (53%) than at 14°C<p align="left">(23%), 48 HAT. In ‘Pioneer 3897’ over 65% and 30% of</p><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left">the total</p></span></span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left"> </p></span></span></p><p align="left"><span style="font-size: xx-small; font-family: TimesNewRomanPSMT;"><span style="font-size: xx-small; font-family: TimesNewRomanPSMT;">14</span></span><span style="font-size: small; font-family: TimesNewRomanPSMT;"><span style="font-size: small; font-family: TimesNewRomanPSMT;">C-activity present in plant extracts was recovered<p align="left">as the parent compound within 24 HAT, at 14°C and</p><p align="left">21°C, respectively. However, in ‘Cargill 2127’ detoxification</p><p align="left">of rimsulfuron was not affected by temperature, and</p><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left">27% of the</p></span></span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left"> </p></span></span></p><p align="left"><span style="font-size: xx-small; font-family: TimesNewRomanPSMT;"><span style="font-size: xx-small; font-family: TimesNewRomanPSMT;">14</span></span><span style="font-size: small; font-family: TimesNewRomanPSMT;"><span style="font-size: small; font-family: TimesNewRomanPSMT;">C-total activity was recovered as the parent<p align="left">compound. Crude ALS extracts from ‘Pioneer 3897’ and</p><p align="left">‘Cargill 2127’ maize seedlings were treated with various</p><span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left">doses (0.001, 0.005, 0.01, 0.1 and 1.0</p></span></span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left"> </p></span></span></p><p align="left"><span style="font-size: small; font-family: SymbolMT;"><span style="font-size: small; font-family: SymbolMT;">μ</span></span><span style="font-size: small; font-family: TimesNewRomanPSMT;"><span style="font-size: small; font-family: TimesNewRomanPSMT;">M) of rimsulfuron.<span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left">Based on ALS specific activity, I</p></span></span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left"> </p></span></span></p><p align="left"><span style="font-size: xx-small; font-family: TimesNewRomanPSMT;"><span style="font-size: xx-small; font-family: TimesNewRomanPSMT;">50 </span></span><span style="font-size: small; font-family: TimesNewRomanPSMT;"><span style="font-size: small; font-family: TimesNewRomanPSMT;">values differed sligthly<span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left">between the two hybrids (I</p></span></span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left"> </p></span></span></p><p align="left"><span style="font-size: xx-small; font-family: TimesNewRomanPSMT;"><span style="font-size: xx-small; font-family: TimesNewRomanPSMT;">50 </span></span><span style="font-size: small; font-family: TimesNewRomanPSMT;"><span style="font-size: small; font-family: TimesNewRomanPSMT;">‘Pioneer 3897’ = 0.091 </span></span><span style="font-size: small; font-family: SymbolMT;"><span style="font-size: small; font-family: SymbolMT;">μ</span></span><span style="font-size: small; font-family: TimesNewRomanPSMT;"><span style="font-size: small; font-family: TimesNewRomanPSMT;">M<span style="font-family: TimesNewRomanPSMT; font-size: small;"><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left">and I</p></span></span></span><span style="font-family: TimesNewRomanPSMT; font-size: small;"><p align="left"> </p></span></span></p><p align="left"><span style="font-size: xx-small; font-family: TimesNewRomanPSMT;"><span style="font-size: xx-small; font-family: TimesNewRomanPSMT;">50 </span></span><span style="font-size: small; font-family: TimesNewRomanPSMT;"><span style="font-size: small; font-family: TimesNewRomanPSMT;">‘Cargill 2127’ = 0.142 </span></span><span style="font-size: small; font-family: SymbolMT;"><span style="font-size: small; font-family: SymbolMT;">μ</span></span><span style="font-size: small; font-family: TimesNewRomanPSMT;"><span style="font-size: small; font-family: TimesNewRomanPSMT;">M). These results suggest<p align="left">that the mechanism of rimsulfuron tolerance in maize</p><p align="left">could be mainly explained by differential herbicide uptake</p><p align="left">and detoxification, with translocation and ALS sensitivity</p><p align="left">having little effect on differential tolerance of these maize</p><p align="left">hybrids to rimsulfuron. On the other hand, the greater</p><p align="left">uptake and translocation of rimsulfuron at 21°C, compared</p><p align="left">to 14°C, could explain the observed herbicide injury in</p><p>maize at high temperatures under field conditions.</p></span></span></p><p> </p>