| In recent years, herbicides were applied widely. The resistance of weeds came into being, and become serious. The problem became one of the center question for discussion in the international weeds research.tribenuron -methyl was widely used in the wheat's field as one of important acetolactate synthase (ALS) inhibitors. This paper studied the effect of pyruvic acid assistance factor dosage and reactive condition on the ALS activity, the resistance of the wheat weeds from different regions, effect of different dose of tribenuron-methyl on growth of tobacco callus, different tolerance and mechanism of various wheat variety against tribenuron-methyl, on the baise of study of the target enzyme of tribenuron-methyl acetolactate synthase and the main plant herbicides metabolic enzyme glutathione-s-transferase (GST) , for the sake of find the mechanism of resistance and tolerance . The results could be summarized as follows: 1. wheat (Lumai22) , tobacco (NC-82), Silene conoidea L., Capsella bursa-pastoris and Descurainia sophia(L.)Schur Medik as the experimental materials, at the condition of in vitro tested the effect of temperature, pH value, dosage of pyruvic acid and other assistance factors (TPP, FAD, Mg~2+) on its activity. The requirements of the reaction conditions of 5 ALS were resemblant. The ALS activity of the 5 plants was enhanced as increasing of temperature, at 20-40℃ the activity was increase stably, and at 45℃ activity reached the peak value, but when temperature was higher than 45℃, the activity lost quickly. When reaction system's pH valve between 3.0-7.0, ALS activity were enhancedas increasing of pH, and reached the peak value when pH=7.0, and when pH=7.5 the activity was slightly reduced, the relative activity was 96.5. When pyruvic acid dosage was 25mmol/L, the reaction was saturated. Low dosage of three assistance factors TPP, FAD and Mg2+ could increase ALS activity observably, and when the dosage of TPP was 0.16 mmol/L, FAD was 3.1umol/L and Mg2+ was 0.08mmol/L, the reaction was saturated.2. The tribenuron -methyl resistance of Silene conoidea L., Capsella bursa-pastoris andDescurainia sophia(L.)Schur Medik from Shandong Province Tai'an Tianzhufeng beauty spot and Qingdao Jiaozhou city. After 5 years use of tribenuron -methyl, the weeds of wheat field form Jiaozhou city had the resistance, and the RI was 3.39. 1.86> 3.13. After treated by the 10% tribenuron -methyl WP18 a.i.g ? hm"2, the weeds ALS activities of Tai'an population and Jiaozhou population were inhibited, and the inhibition rates were reduced slowly after 10-20 days. Silene conoidea L., Capsella bursa-pastoris and Descurainia sophia(L.)Schur Medik of Tai'an population died out respectively after 25, 20, 30 days and the ALS inhibition rates were 66.5%, 80.2% and 78.4% , but at that time the ALS inhibition rates of the Jiaozhou population were only 36.5%, 59.4%, 30.4% which were lower than the Tai'an pollution obviously. The ALS of the 3 weeds of Tai'an population were more sensitive to tribenuron-methyl in vitro than the Jiaozhou population, that IC50 was only 135.2, 123.5, 146.5 nmol/L, and IC50 of Jiaozhou population was 223.2, 180.1, 253.5 nmol/L. After treated by the 10% tribenuron -methyl WP18 a.i.g ? hm"2, the GST activity of Silene conoidea L. was induced after 1 day, and came back in 5 days. GST activity of Capsella bursa-pastoris and Descurainia sophia(L) Schur Medik of 2 population shaped a curve of 1 peak with the time, GST activity reached the peak value at 3 days (4 days , Descurainia sophia(L)Schur Medik of Jiaozhou population), and than reduced. Then we could presume that the reduce ofALS sensitivity against tribenuron-methyl was the main causation.3. Embryonic callus derived from tobacco (NC-82) were transferred on MS culture medium substrate with different dose of tribenuron-methyl to select for 12 generations. The resistances of callus to tribenuron-methyl were enhanced during subculture, resistant index was 1.4, 3.6, 11.6 and 18.5 with selective dose 4.2, 10.8, 34.9, 55.7 ai.mg.L"1 at 12th subculture, and the ALS sensitivity to tribenuron-methyl was reduced. The speed of tobacco callus resistance was higher in the higher dose. Regenerative plantlet treat with high dose of 10% tribenuron-methyl in 20 a.i.g ? hm~2, and the survival rate was 5.8, 27.3, 43.8 and 63.3%, the revulsive resistance can be give expression in the all plant. The sensitivity of ALS against tribenuron-methyl in vitro was different and the IC50 was 376.5, 378.4 and 379.8 nmol/L, these was higher than the valve of the new tobacco callus. During subculture the regenerative rate of callus was reduced and engendered slight resistant, but these had nothing to do with the disposal of tribenuron-methyl.4. We m easured t he t olerance o f v arious w heat v arieties a gainst t ribenuron -methyl, Bima 4 hao and Weimai 8 hao had high resistance and the IC50 were 502.6a.i.ug/kg and 409.3a.i.fig/kg, Jil3 hao's IC50 was 156.9a.i.ng/kg, and Lumai 22 and Huangxiandali were susceptive and IC50 were under 45.0a.i.ng/kg. But these 5 wheat varieties' target enzyme of tribenuron -methyl acetolactate synthase had no obvious difference on sensitivity against tribenuron-methyl, and indeed Huangxiandali IC50 (154.2nmol/L) was higher than Weimai 8 hao (149.3nmol/L). Wheat ALS activity could come back from the inhibit of tribenuon-methyl rapidly, Bima 4 hao and Weimai 8 only needed 1.5 day, but the susceptive varieties needed 3 days. Bima 4 hao and Weimai 8 hao GSTs had higher respondent scope and shorter time than the susceptive varieties, and they reached the peak value 1.46 and 1.42 on the second day. Ji 13 hao, Lumai 22 and Huangxiandali reached the peak value 1.39, 1.33, 1.32 on the third day.The result of the study showed that the reason of various wheat varieties have different tolerance against tribenuron -methyl was not the difference of sensitivity of ALS, but the enhance of wheat GST activity.
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