Metabolism of bifenox in soil and plants

The herbicide, methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate (bifenox), had a half-life of 3 to 7 days after preemergence application to a greenhouse soil mix. Metabolites identified included: 5-(2,4-dichlorophenoxy)-2-nitrobenzoic acid, 2,4-dichlorophenyl 4-nitrophenyl ether (nitrofen), and 5-(2,4-dichlorophenoxy)anthranilic acid over a 313-day sampling period. Comparison of the total ¹⁴C in the soil to that extractable by methanol showed an increase in the proportion of bound material. The major metabolite eluted from a Frederick clay loam soil column was identified as the acid of bifenox and its mobility was associated with the short half-life of bifenox in soil. In vitro studies with shoot-tissue macerates showed that bifenox was not degraded by corn (Zea mays L.) or soybeans (Glycine max (L.) Merr.) and was degraded to less than 1% by velvetleaf (Abutilon theophrasti Medic.).     

Chemical weed control in irrigated direct-seeded rice in the Sudan Gezira

Unrestricted weed growth resulted in serious yield losses (60–75%) in rice (Oryza saliva L.). Hand-weeding once at 2 weeks after crop emergence was ineffective, but weeding at 2 and 2 weeks after crop emergence brought yield losses down to 20%. Pre-emergence application of bifenox and oxadiazon (12 l) and post-emergence application of molinate + propanil gave crop yields comparable to that of the clean weeded control (91–129%). Grain yields obtained with pre-emergence application of oxadiazon (25 EC) and post-emergence applications of propanil, bentazone + propanil, and bifenox alone or as a tank mix with propanil or bentazone were considerably less than those obtained from the clean weeded plots. Bifenox, oxadiazon (12 l) and propanil + molinate gave adequate and persistent weed control (72–97%), and did not damage rice. Oxadiazon (25 EC) gave good weed control but resulted in a serious stand reduction. Post-emergence application of propanil, propanil + bentazone bifenox alone or as a tank mix with propanil or bentazone had no adverse effect on crop stand, but gave poor control of grasses (0–40%).     

Effects of LS 82556 on thylakoid activities and photosynthesis: A comparison with paraquat and acifluorfen

LS 82556 is a new phytotoxic compound inducing photodependent herbicidal effect. In isolated cucumber cotyledons maintained under our experimental conditions, on water without sucrose and under continuous light, LS 82556 induces a photodependent degradation of biological membranes, the symptoms of which are near those of paraquat under the same conditons. The inhibition of the photosynthetic electron transfer by diuron, atrazine, or phenmedipham prevents this phytotoxic action. Using class C and class A chloroplasts isolated from spinach leaves and from cucumber cotyledons, it was shown that LS 82556 is neither an uncoupler nor an inhibitor of the electron transfer, nor is it an electron acceptor. Moreover, it is without effect on the CO₂-dependent O₂ evolution of intact chloroplasts (class A) under light. When isolated thylakoids were subjected to a 400 μE m⁻² sec⁻¹ photosynthetically active radiation light for 10 to 25 min, LS 82556, up to 100 μM, did not change the thylakoids activities. All these results show that the photodependent toxic effect of LS 82556 is quite different from that of paraquat, but it is near that of the diphenyl ethers such as acifluorfen. They demonstrate that the direct involvement of the thylakoid electron transfer in the photodependent mode of action of LS 82556 is unlikely. In isolated cucumber cotyledon fragments, under our conditions, this phytotoxic effect of LS 82556 seems to depend on the presence of sufficient amounts of carbohydrates, which are normally provided through photosynthesis.     

Diquat enhancement of cupric ion toxicity

Cupric ion inhibition of Chlorella growth and photosynthesis and electron transport in isolated chloroplasts was enhanced by concentrations of diquat (6,7-dihydrodipyrido[1,2-a:2′,1′-c]pyrazinediium) that did not inhibit these processes in the absence of cupric ions. Diquat decreased the lag in cupric ion inhibition of Chlorella photosynthesis from 5 to 3.3 min. Diquat enhancement of cupric ion toxicity was immediate with no lag when diquat was added to Chlorella cells with photosynthesis inhibited by cupric ions. Diquat was absorbed by isolated chloroplasts with an intact outer envelope and the absorption was not due to diquat binding to chloroplast membranes. Cupric ion movement through the outer envelope of chloroplasts was stimulated by the presence of diquat. Cupric ion toxicity was also increased by diquat in bicarbonate solutions. The optimum molar ratios of cupric ions to diquat among those tested for diquat enhancement of cupric ion toxicity were 1:0.188 and 1:0.2, which are 1:1 and 1:1.08 on a parts per million basis.     

Diphenylether-like physiological and biochemical actions of S-23142, a novel N-phenyl imide herbicide

Several physiological and biochemical actions of a new experimental herbicide, S-23142 [N-(4-chloro-2-fluoro-5-propargyloxyphenyl)-3,4,5,6-tetrahydrophthalimide], have been investigated. S-23142 was active under the presence of light and oxygen. Photosynthetic CO₂ fixation in soybean began to decrease 4–5 hr after the foliar treatment of S-23142, being accompanied by the appearance of visible bleaching and wilting of the plants. A large amount of ethane, the products of peroxidation of unsaturated fatty acids, was produced from the cotyledon discs of cucumber (Cucumis sativus L.) treated with S-23142. Leakage of ATP was also observed. S-23142 did not inhibit photosynthetic oxygen evolution of the discs just after the application; however, the oxygen evolution rate decreased as the treated discs produced ethane. The results suggest that cell membrane and chloroplast membrane were deteriorated by the membrane lipid peroxidation. S-23142 also induced ethylene production and a high level of phenylalanine-ammonia lyase activity in cucumber cotyledon, which was regarded as the phenomena of stress response. Only the ethylene production was inhibited by aminoethoxyvinylglycine and cycloheximide, while the ethane production was not affected. All of these actions of S-23142 were essentially the same as those of acifluorfen ethyl except that the activity of S-23142 was more than 10 times higher than that of acifluorfen ethyl. These data strongly suggest that S-23142 belongs to the same group as diphenylethers in its mechanisms of action despite the difference in chemical structure.     

Weed control in direct-seeded lowland rice under poor water control conditions

Several herbicides applied singly and in combination were evaluated for weed control and for their effects on crop yield in direct-seeded lowland rice under poor water management conditions characteristic of the conditions in which lowland rice is grown by most farmers in West Africa. Several herbicides including cyperquat at 3.0 kg/ha, a mixture of cyperquat and 2,4-D at 2.0 + 0.5 kg/ha, bentazon at 2.0 kg/ha and avirosan satisfactorily controlled sedges in the 3-year study. Crop yield was consistently high in plots where weeds were controlled with post-emergence application of MCPA + propanil at 1.0+1.7 kg/ha, propanil + thiobencarb 2.2+1.2 kg/ha, oxadiazon 1.5 kg/ha, bentazon 2.0, granular 2,4-D at 1.0 kg/ha, and a pre-emergence application of bifenox at 2.0 kg/ha. Crop yields in plots treated with these herbicides were generally better than with two hand-weedings.     

Physiological actions of dinoterb,a phenol derivative: 1. Physiological effects on the whole plant and on tissue fragments of pea

The herbicide dinoterb is a tert.-butyl-2-dinitro-4,6-phenol. Its effects on the metabolism (water, dry matter, nitrogen, chlorophyll, and flavonol contents) were studied on pea plants (Pisum sativum L.). Concurrently, photosynthesis and respiration intensities of treated plants or tissues were measured (O₂ emission or uptake measured on leaf fragments in the reaction vessel of a Clark-type electrode system). Dinoterb, which is an inhibitor of photosynthesis of isolated, physiologically active chloroplasts, also appeared to rapidly inhibit photosynthesis in the whole plant. This property was used for an indirect method of analysis of dinoterb movement in the leaf and in the plant. Dinoterb appears to have a complex mode of action: low concentrations of the herbicide, rapidly appearing in the whole treated leaf, inhibited photosynthesis, uncoupled oxidative phosphorylations, and began to inhibit respiratory oxygen consumption. High concentrations of dinoterb were responsible for important necrosis some days after treatment and we could show, by analysis of the flavonolic accumulation, that cells of the upper epidermis seemed to be first affected.     

Diphenyl ether-chloroplast interactions

The diphenyl ethers acifluorfen (sodium-5-[2-chloro-4-(trifluoromethyl)-phenoxyl]-2-nitrobenzoate), acifluorfen-methyl (methyl-5-[2-chloro-4-(trifluoromethyl)-phenoxyl]-2-nitrobenzoate), and oxyfluorfen (2-chloro-1-[3-ethoxy-4-nitrophenoxy]-4-(trifluoromethyl)benzene have an absolute light requirement for herbicidal activity. CO₂-dependent O₂ evolution was inhibited in leaf disks obtained from 5-week-old spinach plants as a result of incubation in the light in the presence of each of the three diphenyl ethers. I₅₀'s were determined for inhibition by the diphenyl ethers of CO₂-dependent O₂ evolution in intact chloroplasts obtained from three species of varying susceptibilities (spinach, coffeeweed, and pea). Rankings obtained correlated well with relative susceptibilities and with relative effectiveness of the three compounds tested. Coupled and uncoupled photosynthetic electron transport in susceptible species were unaffected by the three compounds at concentrations in the I₅₀ range. Exposure to herbicidally inactive isomeric analogs of oxyfluorfen and acifluorfen did not affect photosynthesis in leaf disks but was effective in inhibiting photosynthesis in isolated chloroplasts. Photosynthetic abilities of intact tissue were not affected by herbicide treatment in red light. Red light was, however, as effective as white light in mediating the inhibition of photosynthesis in isolated intact chloroplasts by diphenyl ethers. The existence of two photoreceptors for diphenyl ether action, one located at the chloroplast envelope and a second outside of the chloroplast, is suggested as a possible basis for these findings.     

甲羧除草醚的合成

介绍了甲羧除草醚的合成方法。以间氯苯甲酰氯、异丙醇酯化生成氯苯甲酰异丙酯,然后经硝化、缩合醚化,酯交换共4步反应得到了2,4-二氯苯基-3’-甲氧基甲酰基-4’-硝基苯基醚。该方法避免了其它路线的种种缺点,具有收率高、产品纯度高和成本低等优点,合成总收率为(以间氯苯甲酰氯计)72.4%,产品纯度达到97.6%。最终目标产物结构通过红外IR、核磁共振H’NMR进行了表征。     

Effects of various classes of herbicides on four species of algae

Chlorella pyrenoidosa, Chlorococcum sp., Lyngbya sp., and Anabaena variabilis were cultured in Bold's basal medium. They were treated with 0.1, 1.0, and 10 μM concentrations of 2-chloro-2′, 6′-diethyl-N-(methoxymethyl)acetanilide (alachlor), 2-chloro-4-(ethylamino)-6-(tert-butyl-amino)-s-triazine (terbuthylazine), 2-sec-butyl-4,6-dinitrophenol (dinoseb), 1,1-dimethyl-3-(α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine) (profluralin), 2, 4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne), and (2,4-dichlorophenoxy)acetic acid (2,4-D). Growth of all algal species tested was markedly reduced by the triazines. Alachlor, dinoseb, and fluometuron inhibited growth of some algae at higher concentrations while 2,4-D and profluralin did not inhibit growth at the concentrations tested. Photosynthesis was greatly inhibited by the triazines, even at the 0.1 μM concentration. Fluometuron was very toxic to the blue-green algae but had less effect on the green algae tested. Lyngbya was most susceptible to photosynthesis reduction by the herbicides. The concentrations of herbicides tested had little effect on respiration of the algae species. It appears that effects on algal growth were due primarily to inhibition of photosynthesis rather than to other metabolic processes.     

Pyoluteorin production byPseudomonas fluorescens strain CHA0 is involved in the suppression ofPythium damping-off of cress but not of cucumber

Pseudomonas fluorescens strain CHA0 is an effective biocontrol agent of various soilborne pathogens. It controls damping-off or root rot caused byPythium ultimum on cucumber, wheat and cress. Strain CHA0 synthesizes several antibiotic metabolites such as hydrogen cyanide, 2,4-diacetylphloroglucinol, and pyoluteorin. The role of pyoluteorin in the suppression of damping-off was investigated. Two Tn5 mutants (CHA660 and CHA661) of strain CHA0 were isolated which had lost the capacity to produce pyoluteorin but still produced 2,4-diacteylphloroglucinol and HCN. These mutants still inhibitedP. ultimum on malt agar (which favours the production of 2,4-diacetylphloroglucinol) but had partially lost the ability to inhibit this pathogen on King's B agar (which favours the production of pyoluteorin). The two pyoluteorin-negative mutants showed a reduced capacity to suppress damping-off of cress caused byP. ultimum but were as effective in the protection of cucumber against this pathogen as the wild-type strain.These results indicate that, depending on the plant, pyoluteorin production plays a role in the suppression of damping-off by strain CHA0 without being a major mechanism in disease suppression. We suggest that the contribution of pyoluteorin to the biocontrol activity of strain CHA0 is determined by the quantity of this antibiotic produced in the rhizosphere, which might depend on the root exudates of the host plant.     

Comparative effects of dichlobenil and its phenolic alteration products on photo- and oxidative phosphorylation

Effects of dichlobenil (2,6-dichlorobenzonitrile) and its phenolic degradation products (2,6-dichloro-3-hydroxybenzonitrile and 2,6-dichloro-4-hydroxybenzonitrile) were compared on electron transport and phosphorylation in isolated spinach (Spinacia oleracea L.) chloroplasts and mung bean (Phaseolus aureus Roxb.) mitochondria. In chloroplasts, the hydroxylated derivatives inhibited both photoreduction and coupled photophosphorylation with water as the electron donor and with ferricyanide as oxidant, and cyclic photophosphorylation with phenazine methosulfate as the electron mediator under an argon gas phase. In mitochondria, the phenolic derivatives acted as uncouplers of oxidative phosphorylation as evidenced by the stimulation of ADP-limited respiration, circumvention of oligomycin-inhibited non-ADP-limited respiration, and the induction of ATPase activity. Treatment of excised mung bean hypocotyls by the phenolic derivatives also resulted in a very rapid and drastic lowering of ATP levels. In all assays, only limited, if any, interference was expressed by dichlobenil even at relatively high molar concentrations.Inhibition of oxidative and photophosphorylation by the phenolic degradation products, but not by dichlobenil, suggests that if there is a delay between the formation of the hydroxylated compounds and their conjugation, photosynthesis and respiration will be inhibited. Because biochemical and physiological processes depend on oxidative and photophosphorylation for the energy (ATP) needed to drive the reactions, interference with ATP production could be one of the major mechanisms through which phytotoxicity is expressed by the phenolic degradation compounds of the herbicide, if they should accumulate in the free from. Species selectivity may be related to the rate of formation of the phenolic products in different plants and the rapidity of conjugate formation.     

Quantitative structure-activity relationships of the inhibition of photosynthetic electron flow by substituted diphenyl ethers

The effect of 41 substituted diphenyl ethers (derivatives of nitrofen and chloroxuron) on photosynthesis in isolated spinach chloroplasts has been studied. All the chemicals were found to be inhibitors of non-cyclic electron transport; the pI₅₀ values varied from 3.17 to 7.16 (I₅₀ is the molar concentration causing 50% inhibition; pI₅₀= -log I₅₀). Based on their structures, the compounds were divided into four groups; for most groups, a correlation between the inhibition of photosynthesis and physicochemical parameters was found. Lipophilicity proved to be the most important parameter; electronic effects did not play a role. Introduction of substituents into the nitrophenyl ring of nitrofen lowered activity considerably. Nitrofen and and chloroxuron analogues seemed to inhibit at different sites in the electron transport chain. A relationship between inhibition of photosynthesis and herbicidal activity was not clear.     

Protoporphyrinogen IX-oxidizing activities involved in the mode of action of a new compound N-[4-chloro-2-fluoro-5-{3-(2-fluorophenyl)-5-methyl-4,5-dihydroisoxazol-5-yl-methoxy}-phenyl]-3,4,5,6-tetrahydrophthalimide

N-[4-Chloro-2-fluoro-5-{3-(2-fluorophenyl)-5-methyl-4,5-dihydroisoxazol-5-yl-methoxy}-phenyl]-3,4,5,6-tetrahydrophthalimide (EK-5385) is an experimental substituted bicyclic herbicide. Soil-applied EK-5385 showed good rice selectivity and potent herbicidal activity on barnyardgrass (Echinochloa crus-galli var. oryzicola) at rates of 3.9-250 g a.i./ha. Barnyardgrass was exhibited normal growth under dark condition, however, the growth of shoot and root was severely inhibited under light condition (14/10 h of light/dark, 50 μmol/m²/s of photosynthetically active radiation) when treated with EK-5385, oxadiazon, and oxadiargyl. IC₅₀ of EK-5385 and oxadiargyl to chlorophyll loss in cucumber cotyledons was approximately 0.3 and 0.7 μM, respectively. IC₅₀ of EK-5385 and oxadiargyl to carotenoids loss in cucumber cotyledons was about 0.26 and 0.1 μM, respectively. IC₅₀ concentration of EK-5385 and oxadiargyl on Protox activity was approximately 5.5 and 8 nM, respectively. Cellular leakage occurred without lag period from cucumber leaf squares treated with 1 μM of EK-5385 and oxadiargyl under light exposure.     

噁草酮耐光解作用与施药技术改进研究

噁草酮对阳光的分解有良好的耐性,用25％乳油2.5L/hm~2防除旱直播稻田杂草,施药后曝晒25d左右药效开始下降,曝晒35～40d的防效仍保持在80％以上,45d后防效较差。施药后等雨或等水灌溉出苗,防除效果好。土壤湿润有利于药效的发挥。     

噁草酮耐光解作用与施药技术改进研究

噁草酮对阳光的分解有良好的耐性,用25％乳油2.5L/hm~2防除旱直播稻田杂草,施药后曝晒25d左右药效开始下降,曝晒35～40d的防效仍保持在80％以上,45d后防效较差。施药后等雨或等水灌溉出苗,防除效果好。土壤湿润有利于药效的发挥。     

Interaction of perfluidone with mitochondrial,thylakoid, and liposome membranes

Perfluidone (1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl]methanesulfonamide) was shown to interfere with phosphorylation and electron transport in isolated mung bean (Phaseolus aureus Roxb.) mitochondria. At low molar concentrations (<100 μM), perfluidone acted as an uncoupler of oxidative phosphorylation as evidenced by stimulation of state 4 respiration, induction of ATPase activity, and circumvention of oligomycin-inhibited state 3 respiration. At higher molar concentrations (>100 μM), perfluidone inhibited electron transport by acting on complexes I and II, and on the alternate (cyanide-insensitive) oxidase. In isolated spinach thylakoids (Spinacia oleracea L.), perfluidone also acted as an uncoupler, at low concentrations, as evidenced by stimulation of photoinduced electron transport with water as the reductant and methyl viologen and ferricyanide as oxidants, and from reduced dichlorophenolindophenol to methyl viologen. In addition, perfluidone inhibited the rate and magnitude of valinomycin-induced mitochondrial swelling in isotonic potassium chloride and potassium thiocyanate, and with thylakoids suspended in potassium thiocyanate at concentrations that inhibited ATP generation (<100 μM). Passive swelling in mitochondria was induced at higher concentrations. The permeability of lecithin liposomes to protons was also increased by perfluidone in a manner characteristic of uncouplers. The results obtained suggested that the partitioning of perfluidone perturbs the inner mitochondrial and thylakoid membranes. The perturbations increase the permeability of the membranes to protons and cations (at least potassium) and decrease membrane “fluidity.” As a consequence of the perturbations, the ATP-generating pathway in both mitochondria and chloroplasts is uncoupled and the structural organization of the electron transport components in mitochondria is disrupted, resulting in multisite inhibition of respiration. No evidence was obtained for a direct interaction between perfluidone and redox components of the electron transport pathways.     

Anti-oxidant response of Cucumis sativus L. to fungicide carbendazim

Our purpose in this research was to determine the response of anti-oxidative enzymes of cucumber (Cucumis sativus L.) when carbendazim applied as soil drench at 0, 5, 50, and 100 mg kg⁻¹. The changes in the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) enzymes were measured in roots, stems, and leaves of cucumber. The plants were sampling at cotyledon phase (14 days) and florescence phase (56 days). A strong correlation between anti-oxidant content and carbendazim concentration was observed. As concentration increased, the activities of SOD and CAT increased in roots and leaves. While in stems, SOD and CAT activities were increased in florescence phase and declined in cotyledon phase. The content of GPX increased in stems, and declined in leaves. Higher levels of SOD, CAT, and GPX were observed in cucumber cotyledons than the older leaves. The present study suggested that carbendazim treatments had different effects on cucumber anti-oxidant system in different tissues. It was concluded that cotyledons might play an important role for adaptation as the carbendazim concentration increased, and the ability of mature cucumber to maintain a balance between the formation and detoxification of activated oxygen species appeared likely to enhance. On the basis of our observations, we conclude that increased SOD, CAT and GPX activity provides plant with increased carbendazim stress tolerance.     

Resistance pattern and antioxidant enzyme profiles of protoporphyrinogen oxidase (PROTOX) inhibitor-resistant transgenic rice

We quantified the resistance levels of transgenic rice plants, expressing Myxococcus xanthus protoporphyrinogen oxidase (PROTOX) in chloroplasts and mitochondria, to PROTOX inhibitors, acifluorfen, oxyfluorfen, carfentrazone-ethyl, and oxadiazon. We also determined whether active oxygen species-scavenging enzymes are involved in the resistance mechanism of transgenic rice. The transgenic rice line M4 was about >200-fold more resistant to oxyfluorfen than the wild-type (WT). M4 was also resistant to acifluorfen, carfentrazone-ethyl, and oxadiazon, but did not show multiple resistance to imazapyr and paraquat, which have different target sites. Acifluorfen, oxyfluorfen, carfentrazone-ethyl, and oxadiazon reduced the chlorophyll content in leaves of WT, but had minimal or no effect on M4. The PROTOX inhibitors also caused significant lipid peroxidation in the treated leaves of WT rice. However, the malondialdehyde production in M4 was not affected by these herbicides. The WT rice had higher activities of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase than M4 after treatment with PROTOX inhibitors. A similar response was observed in all cases of antioxidant isozyme profiles analyzed. However, the induction in antioxidant activity in WT was not enough to overcome the toxic effects of a PROTOX inhibitor so the plant eventually died.     

3-(2-氯-4-三氟甲基苯氧基)-N-芳基苯甲酰胺的合成与植物生长调节活性

为考察对苯氧基苯甲酰胺类化合物的生物活性特点,以3-(2-氯-4-三氟甲基苯氧基)苯甲酸和氯化亚砜为原料先合成得到酰氯,再与取代芳胺反应,得到了8个新的标题化合物。通过IR、1H NMR、MS和元素分析对该系列化合物的结构进行了确证。采用小麦芽鞘法和黄瓜子叶法测定了它们对小麦和黄瓜的植物生长调节活性,结果表明:在10 μg/g浓度下,所有化合物均显示出促进小麦芽鞘伸长的活性,其中3b的促进率为27.08%,高于对照药剂吲哚乙酸IAA(10.10%);而化合物3d、3h则显示了很强的促进黄瓜生根的活性,在10 μg/g浓度下,促进率分别为66.66%和55.55%,显著高于IAA(12.5%)。