Selective herbicidal activity of iodide in relation to iodide accumulation and foliar peroxidase activity

The response of several plant species (dwarf bean, tomato, pea, cabbage, nettle and buttercup) to treatment with iodide has been investigated. Selective toxicity of iodide has been confirmed, sensitive species exhibiting severe desiccation of the leaves. Iodination of cellular components following treatment of bean leaves with iodide has been demonstrated, indicating that the iodide undergoes intracellular oxidation to iodine. This is thought to be brought about by peroxidase enzymes. Peroxidase activities (in relation to iodide oxidation) in the leaves of the plants studied have been determined. Although very low peroxidase activities are correlated with iodide tolerance, the results obtained indicate that the extent to which iodide accumulates in the leaves is also an important contributory factor in iodide selective toxicity.     

Mode of action of thiocyanate and iodide in relation to IAA metabolism

Whole plant studies have reaffirmed that of the halides and pseudohalide thiocyanate, only iodide and thiocyanate possess defoliant properties. Established work has indicated their possible involvement with IAA (indole-3-acetic acid). In vitro studies have suggested that IAA destruction is not through a direct interaction between IAA and the halides and pseudohalide but depends on their conversion to the halogen or pseudohalogen which can then destroy IAA. This may be accomplished by the peroxidase enzyme system for iodide only and docs not provide a mechanism for thiocyanate activity. However, both iodide and thiocyanate have chemical oxidation potentials suitable for their conversion to the halogen or pseudohalogen respectively via the photosynthetic apparatus. Hence, this would provide an explanation for then activity and the apparent inactivity of bromide, chloride and Buoride which would be oxidized very slowly or not at all.     

A specific and sensitive assay to quantify the herbicidal activity of chloroacetamides

Based on a recently discovered property of chloroacetamide herbicides—the inhibition of the incorporation of oleic acid into sporopollenin of Scenedesmus acutus—a rapid quantitative test was developed for chloroacetamide-type herbicidal activity. In this test, algal cells are incubated for 3 h with [¹⁴C]oleic acid, saponified and the lipids (including non-saponifiable ones) extracted and discarded. The radioactivity incorporated into the residual non-lipid fraction is determined, and inhibition of this incorporation is used as a marker of chloroacetamide-type activity. Twenty-two agrochemical compounds were screened in this assay, which was found to be very sensitive, a 50% inhibition being reached with submicromolar herbicide concentrations. It is specific to chloroacetamides and related amides, since all these herbicides tested were potent inhibitors, while other herbicides were not. Highest inhibition was shown by cafenstrole followed by butachlor, fluthiamid, metazachlor, alachlor, dimethenamid, metolachlor and mefenacet. For these herbicides (with the exception of butachlor) sensitivity in the test was positively correlated (r=0·984) with their phytotoxic effect on the alga. © 1998 SCI     

一株高地芽胞杆菌D30202的抑草活性及作用机制初探

为开发新型微生物除草剂, 通过萌发袋法对嗜盐高地芽胞杆菌Bacillus altitudinis菌株D30202抑制杂草种子萌发和幼苗生长的活性进行测定?通过盆栽茎叶喷雾法对不同有机溶剂萃取物的杀草谱和作物安全性进行测定和评价, 并以自生油菜Brassica napus L.为供试杂草对活性菌株的抑草机理进行初探?结果表明, 嗜盐高地芽胞杆菌菌株D30202发酵液的正丁醇萃取物对十字花科杂草自生油菜的除草活性最为显著, 同时对青稞Hordeum vulgare var. coeleste?小麦Triticum aestivum L.表现出较高的安全性?而经正丁醇萃取物处理的自生油菜, 其丙二醛(MDA)含量及抗氧化酶(SOD?POD?CAT)活性呈持续下降趋势, 表明该菌株的抑草作用机理可能是通过影响光合作用等代谢过程实现的?综上所述, 高地芽胞杆菌D30202可开发为禾本科作物田十字花科杂草的生物除草剂?     

环磺酮的除草活性及对玉米的安全性评价

为明确环磺酮在我国玉米田的应用技术和前景,采用温室盆栽法测定环磺酮的杀草谱和对常见杂草的除草活性以及对不同玉米品种的安全性,并通过田间药效试验验证其应用效果。结果表明,在100 g (a.i.)/hm²田间推荐剂量下进行茎叶处理时,环磺酮可以有效防除玉米田常见禾本科、莎草科和阔叶杂草,其中对反枝苋Amaranthus retroflexus、鳢肠Eclipta prostrata的活性较高,鲜重抑制率可达90%以上;对6种常见玉米田杂草稗Echinochloa crus-galli、马唐Digitaria sanguinalis、圆叶牵牛Ipomoea purpurea、反枝苋、碎米莎草Cyperus iria和青葙Celosia argentea的生长抑制中量GR₅₀分别为8.44、17.16、9.37、8.68、9.40和32.51 g (a.i.)/hm²,在供试剂量下环磺酮的除草活性均高于对照药剂硝磺草酮;田间推荐剂量下环磺酮对除黑糯301品种以外的11个玉米品种均较为安全,提高到2倍推荐剂量时,对不同玉米品种的生长抑制均增强;环磺酮对郑单958、珍珠糯8号、苏科甜1506和中糯2号4个玉米品种以及稗、马唐、圆叶牵牛、反枝苋、碎米莎草和青葙6种杂草之间均具有较好的选择性,选择性指数为10.40~29.14。田间药效试验表明,126 g (a.i.)/hm²环磺酮处理茎叶后第28天,对玉米田杂草稗、马唐、狗尾草Setaria viridis、香附子Cyperus rotundus、圆叶牵牛、空心莲子草Alternanthera philoxeroides的总株防效为86.51%,鲜重防效为87.81%,且对供试玉米品种彩甜糯102安全。     

丙炔氟草胺除草活性及对棉花的安全性

丙炔氟草胺是一种以原卟啉原氧化酶为作用标靶的N-苯基肽酰亚胺类除草剂。为探究其在棉花田的应用前景,通过温室盆栽法对丙炔氟草胺的杀草谱、除草活性及其对棉花的安全性进行了测定。结果表明:丙炔氟草胺对棉田常见阔叶杂草有较好防效,处理剂量为有效成分15 g/hm2时,对马齿苋Portulaca oleracea、反枝苋Amaranthus retroflexus、藜Chenopodium album、小藜Chenopodium serotinum和鳢肠Eclipta prostrata的鲜重防效均高于90%,对野油菜Rorippa indica、苣荬菜Sonchus arvensis、小飞蓬Conyza canadensis、龙葵Solanum nigrum、马唐Digitaria sanguinalis和牛筋草Eleusine indica等的鲜重防效高于80%;丙炔氟草胺对棉田4种常见阔叶杂草马齿苋、反枝苋、龙葵和藜的除草活性均显著高于二甲戊灵;丙炔氟草胺在鲁棉研28号与马齿苋、反枝苋、龙葵和藜之间的选择性指数依次为79.1、38.1、32.1和112.6,均显著高于二甲戊灵的12.0、9.9、5.8和9.2;鲁棉研37号、鑫秋4号与杂草间的选择性指数,与鲁棉研28号的相近。试验结果表明,丙炔氟草胺可作为棉田苗前防除阔叶杂草的候选药剂之一。     

Uptake and metabolism as mechanisms of selective herbicidal activity of the 1,2,4-triazolo[1,5-a] pyrimidines

In order to identify the factors providing the triazolopyrimidines with a wide range of selectivity amongst agriculturally important plant species, studies were made on the uptake and metabolism of a representative compound, N-(2,6-dichlorophenyl)-5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine- 2-sulfonamide. This compound is much more phytotoxic to dicots than to monocots. Experiments showed that variations in leaf morphologies and geometries relative to spray applications resulted in different herbicide dosages applied to plant species used in selectivity evaluations. However, this parameter did not have a statistically significant correlation to herbicide selectivity measurements. Characterization of the metabolic pathways showed that the major herbicide metabolites involved methyl hydroxylation or hydroxylation of the aniline ring followed by glucose conjugation. Since these metabolites were not exclusive to either monocots or dicots, herbicide selectivity does not appear dependent on the pathway of metabolism. Studies on the kinetics of metabolism suggest instead that metabolic rate was important. Monocots metabolized the herbicide rapidly and generally were tolerant while the opposite was true of dicots.     

牡丹皮提取物除草活性初步研究

为明确牡丹皮(Cortex Moutan Radicis)的除草活性并初步探索其活性成分分离条件,采用平皿法、土壤喷雾法及茎叶喷雾法测定了牡丹皮不同极性溶剂萃取物对反枝苋Amaranthus retroflexus和稗Echinochloa crus-galli的除草活性。平皿法测定结果显示,在1 mg/mL浓度下,牡丹皮正丁醇萃取物的除草活性最强,对反枝苋幼根和幼茎的抑制率分别为67.88%和65.71%,对稗草幼根和幼茎的抑制率分别为68.72%和71.32%;毒力测定结果表明,牡丹皮正丁醇萃取物对反枝苋幼根和幼茎的IC₅₀分别为12.28 mg/L和19.67 mg/L,对稗草幼根和幼茎的IC₅₀分别为43.35 mg/L和72.79 mg/L。土壤喷雾法和茎叶喷雾法测定结果显示,在5 mg/mL浓度下,牡丹皮正丁醇萃取物对反枝苋和稗草的鲜重抑制率最高,其中土壤喷雾法对反枝苋和稗草的鲜重抑制率分别为81.43%和83.18%;茎叶喷雾法对两种杂草的鲜重抑制率分别为80.83%和83.65%。由此可见,牡丹皮的除草活性成分主要集中在正丁醇...     

4-羟基-3-甲氧基肉桂酸乙酯的生物活性及其除草作用机制

为明确以天然产物阿魏酸为母体进行化学结构改造得到的化合物4-羟基-3-甲氧基肉桂酸乙酯的生物活性及其除草机制,利用茎叶喷雾法和小杯法测定其对马唐和反枝苋的生物活性,基于生理生化指标及功能基因表达量对其除草作用机制进行研究。结果表明:4-羟基-3-甲氧基肉桂酸乙酯对马唐茎叶鲜重抑制中浓度IC50为46.27 mg/L;对反枝苋胚根和芽的IC50分别为129.94 mg/L和147.33 mg/L,且在500 mg/L浓度处理时可抑制反枝苋种子萌发;对拟南芥根长的IC50为43.82 mg/L,在160 mg/L浓度处理时拟南芥几乎停止生长、叶片发黄、根毛堆积。该化合物以1 000 mg/L浓度处理马唐叶片2、3、8 h后,电导率较对照组分别增加了22.70%、18.46%和25.62%;1 000 mg/L浓度处理下叶绿素a/b为2.43,较对照的3.62显著下降;处理后叶表微观结构观察发现化合物浓度越大,植物叶片表皮毛倒伏和褶皱越严重;拟南芥AT4G04820基因表达量显著下降,在处理45 min时下降最显著,与对照组相差42.52倍,微管蛋白含量下降,造成微管解离,从而抑制植物生长。表明4-羟基-3-甲氧基肉桂酸乙酯具有较强的除草活性,可能通过破坏细胞结构、抑制光合作用及阻止根生长等途径使杂草生长受到抑制甚至死亡。     

Glutathione synthesis in response to captan: A possible mechanism for resistance of Botrytis cinerea to the fungicide

Two Botrytis cinerea isolates, field captan-resistant and normal type, were grown in liquid medium for 4 days prior to captan application. The glutathione (GSH) and oxidized glutathione (GSSG) of their mycelium and medium were analyzed at various times during the fifth day of their growth. Only slight differences in GSH levels between the isolates were observed, but marked differences in mycelial GSH were found in response to captan. Following the application of captan, less GSH was produced and after a longer lag period by the normal type of the fungus compared to the resistant isolate. This increase in the GSH level in the resistant isolate could make more nonvital thiol compound available for detoxifying captan and therefore prevent damage the fungicide could cause to the vital protein thiols of fungal cells.     

二氯喹啉草酮与二氯喹啉酸的除草活性及对水稻安全性的比较

采用整株生物测定法测定两种除草剂二氯喹啉草酮与二氯喹啉酸茎叶处理对水稻田杂草的生物活性及对水稻的安全性。结果表明:当二氯喹啉草酮和二氯喹啉酸有效成分剂量均为600 g/hm2时, 两种除草剂对稗属杂草、鳢肠的鲜重抑制率均高于94%, 其GR90为107.35~558.58 g/hm2; 对马唐和耳叶水苋的鲜重抑制率低于85%, 对抗二氯喹啉酸西来稗和千金子的鲜重抑制率低于50%; 不同的是二氯喹啉草酮对丁香蓼和异型莎草的鲜重抑制率分别为92.17%、94.33%, 均显著高于二氯喹啉酸(83.64%, 85.57%)。二氯喹啉草酮和二氯喹啉酸对1.5叶期水稻安全性差, 选择性指数为2.53~3.58; 对3.5叶期水稻安全, 选择性指数大于4, 各处理水稻鲜重与对照组之间无显著差异。本着高效、安全、经济的原则, 不推荐二氯喹啉草酮用于防除水稻田禾本科杂草, 仅对部分阔叶类和莎草科杂草发生严重的水稻田, 二氯喹啉草酮可以作为补充除草剂。     

Environmental factors affecting the herbicidal activity of DPX-A7881

DPX-A7881, methyl 2-[(4-ethoxy-6-methyl-amino-1, 3, 5-triazin-2-yl)carbamoylsulphanoyl] benzoate, is a sulfonylurea herbicide being developed in Canada and Europe for post-emergence broadleaf weed control in spring and winter rapeseed. Growth room studies were conducted to determine the environmental factors affecting the herbicidal activity of DPX-A7881 applied post-emergence on winter rapeseed (Brassica napusu L. ‘Tandem’) and on a closely related weed species, Sinapis arvensis L. (wild mustard). Laboratory tests were carried out at tempera tures ranging from 2–26°C, at relative humidities from near 40% to >95%, with rain-free periods from 0.25–8 h after herbicide application, at soil moisture contents from 50–200% of field capacity, and with irradiances from 23–450 μEm^?2s^?1 Significant control of S. arvensis was demonstrated for all treatments except under poor growing conditions at the lowest temperatures and irradiances tested. After two weeks' exposure to each of the tem perature treatments, the herbicide maintained control of S. arvensis during a subsequent week of favourable growing conditions. Relative humidity, soil moisture or simulated rainfall did not significantly alter the herbicidal activity of DPX-A7881 on S. arvensis. DPX-A7881 showed a high degree of crop safety on B. napus. The herbicide did not significantly reduce the dry weights of B. napus grown under any of the environmental conditions tested.     

天然除草活性化合物研究进展

综述了近年来国内外从天然产物中开发具有除草活性化合物的研究概况,着重介绍一些可能具有除草剂开发潜力的植物和微生物源化合物,并对生物除草剂的发展前景进行了展望.     

尿素除草活性的培养箱实验

以8种杂草为对象,通过培养箱试验研究不同浓度的尿素溶液对供试杂草萌发及根茎生长的影响。供试草种分别为鬼针草(Bidens bipinnata)、杂三叶(Trifolium hybridum)、马蹄金(Dichondra repens)、一点红(Emiliasonchifolia)、水蜈蚣(Kyllinga brevifolia)、狗尾草(Setariae Viridis)、高羊茅(Festuca arundinacea)、多年生黑麦草(Lolium perenne)。结果表明,尿素除对狗尾草的萌发无明显抑制作用外,对其他杂草的萌发、根长、茎长均有明显的抑制作用,并随着尿素溶液浓度的增高抑制作用增强,且以对根长的抑制作用最为明显。尿素对供试草种的萌发和根茎生长的抑制作用存在明显的种间差异,对尿素胁迫最敏感的是三叶草和水蜈蚣,然后分别是鬼针草、一点红、高羊茅、马蹄金、多年生黑麦草,最不敏感的是狗尾草,较低浓度的尿素处理反而促进了狗尾草的萌发。     

阿魏酸衍生物的合成及其除草活性测定

为从天然产物中获取新的除草活性成分,通过化学合成的方法对分离自瓜果腐霉Pythium aphanidermatum代谢产物中的阿魏酸进行了结构改造,并采用小杯法,以马唐、马齿苋和播娘蒿为供试杂草对所得化合物进行了除草活性测定。结果显示:所合成的4-羟基-3-甲氧基肉桂酸乙酯、4-羟基-3-甲氧基肉桂酸邻氯苯胺、4-羟基-3-甲氧基肉桂酸酰肼、4-羟基-3-甲氧基肉桂酸叔丁酯和4-乙酰氧基-3-甲氧基肉桂酸5种化合物的回收率分别为96.81%、97.39%、82.20%、75.67%和98.29%。4-羟基-3-甲氧基肉桂酸酰肼和4-乙酰氧基-3-甲氧基肉桂酸对马齿苋胚根的抑制活性最强,IC50分别为87.50 mg/L和74.86 mg/L,其余3种活性相对较弱;4-羟基-3-甲氧基肉桂酸乙酯和4-乙酰氧基-3-甲氧基肉桂酸分别在500 mg/L和1 000 mg/L浓度下可完全抑制播娘蒿和马齿苋胚根、芽的生长,而4-羟基-3-甲氧基肉桂酸邻氯苯胺则在1 000 mg/L浓度下可完全抑制播娘蒿胚根的生长。表明在阿魏酸分子中的不同位点引入适当的基团结构可以提高或者降低阿魏酸分子的除草活性,并获得新的除草活性物质。     

双环磺草酮与氯氟吡啶酯复配的联合除草活性及对水稻的安全性评价

双环磺草酮是一种新型的对羟基苯丙酮酸双加氧酶抑制剂类除草剂,为明确其除草活性以及其与合成激素类除草剂氯氟吡啶酯复配后的除草效果,采用温室盆栽法研究了二者复配的联合作用类型,以及复配药剂在水稻与杂草之间的选择性,并进行了田间药效评价。温室盆栽试验结果表明:双环磺草酮与氯氟吡啶酯复配后使用,对供试杂草稗草、千金子、异型莎草及鸭舌草均呈现加成或增效作用;其中二者按照质量比5:1复配后的除草活性高于双环磺草酮单剂;复配药剂在供试水稻品种与杂草之间的选择性指数在28.72~54.81之间,与两种单剂相比,复配药剂对水稻的安全性均有提高。田间药效试验结果表明:双环磺草酮与氯氟吡啶酯复配扩大了杀草谱,对稗草、千金子、异型莎草及雨久花的株防效和鲜重防效在93.4%~100%之间,且对水稻安全;其中,田间复配用量为双环磺草酮有效成分120 g/hm^2、氯氟吡啶酯有效成分18 g/hm^2时效果最佳,对4种供试杂草的防效为97.1%~100%。     

丙炔氟草胺与二甲戊灵复配的联合除草作用及对棉花的安全性

为明确丙炔氟草胺与二甲戊灵复配的联合除草作用及其对棉花的安全性,采用室内生物测定方法,研究了复配制剂的联合除草类型,测定了其对不同品种棉花的安全性及其在棉花与杂草之间的选择性指数,并对复配制剂进行田间药效试验。温室试验结果显示:丙炔氟草胺与二甲戊灵按不同质量比复配后,对供试杂草马齿苋、反枝苋和马唐均呈现加成或增效作用。其中丙炔氟草胺与二甲戊灵按质量比1 : 10复配后的除草活性高于二甲戊灵单剂,其在供试棉花品种与供试杂草的选择性指数在25.81~39.39之间,与两种单剂相比,在一定程度上提高了对棉花的安全性。田间药效试验结果显示:丙炔氟草胺与二甲戊灵复配后综合了两种单剂的优势,对铁苋菜、反枝苋、马齿苋、藜和牛筋草均有很好的防除效果且对棉花安全。     

几种天然蛋白原料水解物的除草活性初步研究

以鱼粉、肉骨粉、豆粕、菜籽粕及芡粉等几种天然蛋白原料为底物,以碱性蛋白酶为水解酶制备出天然蛋白原料的水解物,用培养皿生物分析法检测不同蛋白原料水解物在不同浓度(0.5、1、2、5 mg/mL)条件下对杂草野菊种子的生根抑制活性。结果表明:不同蛋白原料制备出的水解物对野菊种子萌发根系生长均有抑制作用,并且随着浓度增加其抑制活性增强,不同蛋白原料水解物的除草活性有显著性差异,其除草活性顺序为:鱼粉水解物>肉骨粉水解物>豆粕水解物>菜籽粕水解物>芡粉水解物,水解物的根抑制活性与原料的蛋白含量及其水解物的多肽含量成正相关性,作者推测,天然蛋白水解物中的多肽可能是植物种子萌发时根系生长抑制活性物质,但这种根抑制活性究竟是由于特异性多肽的化感作用还是植物种子萌发时对高氮胁迫反应有待进一步研究。     

A possible involvement of gibberellin in the mechanism of Avenafatua resistance to triallate and cross-resistance to difenzoquat

Avena fatua L. populations from numerous fields in Alberta have simultaneously developed resistance to recommended rates of two dissimilar herbicides, triallate and difenzoquat. We used exogenous applications of gibberellic acid (GA₃) to investigate the possibility that endogenous gibberellins were involved in the A. fatua 's resistance mechanism. For control plants, without applied GA₃, shoots of the most resistant (R) populations emerged more rapidly and elongated faster than shoots of the susceptible (S) populations. Increases in shoot elongation in response to exogenous GA₃ were significantly lower in R populations compared with S populations. This suggests that R populations may have elevated endogenous gibberellin levels, relative to S populations. Additionally, inhibition of S population shoot elongation and shoot anatomical abnormalities caused by relatively low concentrations of triallate and difenzoquat could be prevented by exogenous application of GA₃. These results suggest that there may be a phytohormonal involvement in the mechanism of triallate/difenzoquat resistance in A. fatua . That is, higher endogenous gibberellin levels in R populations may result in meristematic growth that is rapid enough to preclude phytotoxic levels of these herbicides from reaching the shoot meristem, which is the likely site of action.     

Chlorfenprop-methyl: its hydrolysis in vivo and in vitro and a new principle for selective herbicidal action

Chlorfenprop-mèthyl is hydrolysed completely as soon as it penetrates the leaf in sensitive as well as in resistant plants. The product of hydrolysis chlorfenprop presumably is the herbicidally active compound. The in vitro hydrolysing activity has been characterized. The behaviour of the herbicide in a system for the detection of rapid herbicidal activity (leaching system) and in three auxin-dependent systems leads to the conclusion, that a difference at the site of action is the basis for the observed herbicidal selectivity.