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1.
Plant pathogenic bacteria in recirculated greenhouse water were inactivated by two distinct photochemical approaches: photo-inactivation in the presence of 0.005% to 0.01% hydrogen peroxide (H2O2), and photocatalytic inactivation with 0.01% titanium dioxide (TiO2). In both processes photo-inactivation is achieved by exposure to sunlight. Total inactivation, with 6–8 log units decrease in viable counts, was achieved in the study of the phytopathogensErwinia carotovora (E.c.), Clavibacter michiganensis (C.m.) andPseudomonas syringae pv.tomato (P.t.) by 10 to 30 min solar irradiation, in the presence of 0.15 to 0.3 mM (50–100 mgl −1) H2O2. Different responses of the examined pathogens towards TiO2 photo-inactivation were noticed. Whereas 10 min of solar illumination in the presence of both 100 mgl −1 H2O2 and 100 mgl −1 TiO2 resulted in total inactivation ofP.t. andE.c., this treatment had no effect onC.m. However, with traces of H2O2 (e.g. 50–100 mgl −1), and in the absence of TiO2,C.m. was deactivated by 20 min of solar irradiation.P.t. was fully inactivated in the dark by H2O2 at 3,000 mgl −1 (0.3%), but not with H2O2 at ≤ 1000 mgl −1. Also, no inactivation occurred with solar illumination in the absence of H2O2. The mechanism of the bactericidal photoreaction and the special significance of plant pathogen inactivation by natural sunlight in the presence of trace levels of H2O2 is discussed. http://www.phytoparasitica.org posting May 20, 2005.  相似文献   

2.
Growing chick‐pea in sustainable systems requires the use and development of more competitive genotypes which can complement the effects of reduced input weed control. A 2‐year study assessed the competitive ability of 13 genotypes grown in either the presence or absence of weeds, in a split‐plot design including the weeds in pure stands. Crop and weed density, phenology, relative biomass of crop (RBc) and weeds (RBw), crop yield characters, crop biometric traits in the absence of weeds, relative biomass total of mixtures (RBT) and crop competitive ability (Cb = ln RBc/RBw) were recorded. Lines C136, C120, C101 and C106, and cultivars Pascià, Visir and Sultano gave the best seed yield in the absence of weeds (1.8–2.0 t ha?1 DM). Weeds reduced yield by 75% and 83% in C136 and C133 and by 87–97% in the other genotypes. Weed biomass in mixture (mainly Chenopodium album) averaged 4.42 t ha?1 DM. Chick‐pea genotypes C136 and C133 were the most competitive, but weeds were more competitive than any of the chick‐peas. Cb was correlated directly to the height of first fertile pod (r2 = 0.84) and inversely to the insertion angle of primary branches to the vertical (r2 = 0.77). Intergenotypic variation for competitive ability could be exploited in integrated weed control using more competitive genotypes, or used in breeding programmes aimed to develop highly competitive cultivars on the basis of easily screenable characters.  相似文献   

3.
A Pseudomonas sp. which grew on 4-chloroaniline as a sole source of carbon and nitrogen was able to degrade 15% of 0.05 mM [14C]3,4-dichloroaniline to 14CO2 within 10 days in presence of 1.5 mM 4-chloroaniline. The catabolic enzymes which degraded 3,4-dichloroaniline to CO2 were inducible by 4-chloroaniline and by 3,4-dichloroaniline. However, their activity was much lower on 3,4-dichloroaniline than on 4-chloroaniline. The strain showed no significant growth on 3,4-dichloroaniline as a sole source of carbon and nitrogen. Soils supplemented with [ring-14C]propanil and the Pseudomonas sp. evolved 25–50% 14CO2 within 5 days. The 14CO2 evolution remained below 1% in absence of the Pseudomonas sp.  相似文献   

4.
The ED50 values and resistance factors of 20 fungicides that all act as inhibitors of the C-14 demethylation of 24-methylenedihydrolanosterol were determined for one wild-type and four resistant strains of Ustilago avenae. All fungicides were cross-resistant to each other; however, the resistance factors varied considerably, ranging from 50 (triadimenol) to 2·2 (miconazole). A tentative structural requirement for low resistant factors was the presence of two phenyl rings separated from each other by at least three atoms. Labeling of lipids with [14C]acetate in the absence and presence of the inhibitors and subsequent sterol analysis revealed that the variable resistance factors were not related to the presence of a second target site. In spite of reported second modes of action of fenarimol, tebuconazole or miconazole, accumulation of C-14 sterol precursors in both sensitive and resistant isolates was necessary to accomplish growth inhibition.  相似文献   

5.
From 2004 to 2006, 213 isolates of Botrytis cinerea never exposed to QO center inhibitors (QOIs) were collected to determine the baseline sensitivity to azoxystrobin. In the absence of salicylhydroxamic acid (SHAM), the mean EC50 values were 10.49 ± 13.12 and 0.36 ± 0.48 mg l−1 for inhibiting mycelial growth and conidium germination, respectively. In the presence of SHAM, the mean EC50 values were 2.24 ± 1.29 and 0.22 ± 0.11 mg l−1. In 2010, five azoxystrobin-resistant isolates were detected with the resistance frequency of 2.25% in greenhouse tomatoes after 4 years of continuous exposure. These resistant isolates showed cross-resistance to other QOIs but not to boscalid. In addition, these resistant isolates had comparable growth, sporulation and pathogenicity ability as sensitive isolates and maintained resistance in plants and the presence of SHAM. The G143A point mutation predicted to cause a change from glycine to alanine at codon 143 of cyt b gene was found in all resistant isolates.  相似文献   

6.
The random amplified polymorphic DNA (RAPD) method was used to investigate the genetic variability and population structure of Fusarium culmorum isolated from wheat stem bases. A total of 108 isolates, representing seven geographically distinct populations, was collected from five climatic regions in Tunisia. Pseudo-allelic frequencies were estimated at each of the 25 putative RAPD loci analyzed by scoring for the presence or absence of amplified fragments; 92 haplotypes were found among the 108 strains. The analysis of the population structure did not reveal any trend with regard to geographic origin. Total gene diversity (HT * = 0.318) was mostly attributable to diversity within populations (HS * = 0.308). Analysis of molecular variance confirmed that most of the genetic variability was within populations. Genetic differentiation among populations was low to moderate (GST * ranged from 0 to 0.190 and averaged 0.041 over all loci). Cluster analysis with UPGMA using genetic distances did not reveal any spatial clustering of the isolates collected from the different geographic regions. Based on these results, we conclude that the F. culmorum isolates recovered from different regions in Tunisia might be part of a single population pool.  相似文献   

7.
The short-term disposition and metabolism of topically administered [14C]chlorpyrifos was assessed in the black imported fire ant (Solenopsis richteri Forel) in the presence and absence of the mixed-function oxidase inhibitor piperonyl butoxide. Chlorpyrifos is readily absorbed into an internal organosoluble fraction which was quickly converted into a water-soluble fraction. The radioactivity was slowly excreted over a 24-hr period. Piperonyl butoxide slowed the conversion of the internal organosoluble radioactivity to the water-soluble fraction. Thin-layer chromatography indicated that piperonyl butoxide slowed the conversion of chlorpyrifos to material remaining at the origin, presumably water-soluble metabolites. The results of acid hydrolysis studies indicated that the water-soluble radioactivity was comprised mainly of conjugates. Although very little chlorpyrifos oxon was recovered in the metabolism experiments, in vitro studies on fire and head homogenates showed the compound to be an extremely potent anticholinesterase, with an I50 of 4.6 × 10?10M, while a major metabolite, 3,5,6-trichloropyridinol, was an ineffective acetylcholinesterase inhibitor.  相似文献   

8.
In this paper, a DSC and Raman study of hydrated multilamellar DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) and DMPE (1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine) liposomes in presence of increasing amounts of DDT is reported.The observed changes denote that DDT molecules interact with both phospholipids and that the interaction mainly involves the external part of the bilayer since the deep penetration into the hydrophobic core is prevented by the setting up of polar interactions between the three aliphatic C-Cl bonds of the trichloro group of DDT and the -N+(CH3)3 of DMPC or the -NH3+ groups of DMPE molecules.This behaviour was particularly evidenced in presence of DMPE, as the insertion of DDT molecules into the central part of the bilayer seems to be completely excluded.Moreover, in DMPE liposomes the overall structure of the bilayer changes to a well defined and structured ‘phase II’ in presence of even small DDT amounts.  相似文献   

9.
The ability of o,p′DDT to bind to the 8S moiety in the uterine cytosol or to interfere with the binding of 3H-estradiol-17β (3H-E2) to that binding component was investigated utilizing a 10–30% sucrose gradient sedimentation analysis. Attempts to demonstrate the binding of radiolabeled o,p′DDT to the 8S receptor in the mouse and rabbit were not successful, presumably due to the relatively low specific activity of the radiolabeled o,p′DDT, however, binding to the “nonspecific” 4S site(s) was detected. On the other hand, the addition of nonlabeled o,p′DDT inhibited the binding of 3H-E2 to the 8S receptor. Thus, o,p′DDT (2 μM) suppressed by 58% the binding of 3H-E2 (2 nM) in the 8S region in ovariectomized adult mice. Similarly, in immature rats three concentrations of o,p′DDT (16, 32, and 96 μM) inhibited by 39.5, 52.9, and 59.7% respectively, the binding of 3H-E2 (2.8 nM). Similar results were obtained with uterine preparations from mature rats. However, the suppression of binding of 3H-E2 in the 8S region resulted in an increased binding in the 3–4S region.A Scatchard plot analysis of the binding of 3H-E2 in the presence of o,p′DDT revealed the same number of binding sites as in the absence of o,p′DDT, indicating that o,p′DDT did not “destroy” the binding capacity. Also, this analysis revealed that o,p′DDT merely caused a decrease in the ratio of the bound to free E2, indicating that o,p′DDT binds to the receptor and thus interferes with E2 binding.In addition, our observations that the administration of o,p′DDT to immature female rats causes a marked increase in the levels of the uterine nuclear binding sites (nuclear estogren receptor) is a further indication that o,p′DDT acts as a typical estrogenic compound. However, whether o,p′DDT has antiestrogenic activity as well has not been established.  相似文献   

10.
The interactions of natural pyrethrins and nine pyrethroids with the nicotinic acetylcholine (ACh) receptor/channel complex of Torpedo electric organ membranes were studied. None caused significant reduction in [3H]ACh binding to the receptor sites, but all inhibited [3H]perhydrohistrionicotoxin ([3H]H12-HTX) binding to the channel sites in presence of carbamylcholine. Allethrin inhibited [3H]H12-HTX binding noncompetitively, but [3H]imipramine binding competitively, suggesting that allethrin binds to the receptor's channel sites that bind imipramine. The pyrethroids were divided into two types according to their actions: type I, which included pyrethrins, allethrin, bioallethrin, resmethrin, and tetramethrin, was more potent in inhibiting [3H]H12-HTX binding and acted more rapidly (i.e., in <30 sec). Type II, which included permethrin, fluvalinate, cypermethrin and fenvalerate, was less potent and their potency increased slowly with time. Also, inhibition of the initial rate of [3H]H12-HTX binding by type I compounds increased greatly by the presence of the agonist carbamylcholine, but this was not so with type II compounds. The receptor-regulated 45Ca2+ flux into Torpedo microsacs was inhibited by pyrethrins and pyrethroids, suggesting that their action on this receptor function is inhibitory. There was very poor correlation between the potencies of pyrethrins and pyrethroids in inhibiting [3H]H12-HTX binding and their toxicities to house flies, mosquitoes, and the American cockroach. However, the high affinities that several pyrethroids have for this nicotinic ACh receptor suggest that pyrethroids may have a synaptic site of action in addition to their well known effects on the axonal channels.  相似文献   

11.
The physiological and biochemical mechanisms of organogenesis in Equisetum arvense have not been clarified yet. However, high concentrations of nitrogen have been shown to exert an inhibitory effect on in vitro tuber formation in E. arvense. The aim of this study was to clarify the influence of the form of nitrogen in a medium on in vitro organogenesis in E. arvense. Single‐node segments of E. arvense rhizomes were cultured in the test medium. The NH4‐N and NO3‐N concentrations of the test medium, respectively, were adjusted by adding NH4H2PO4 and KNO3 to the basal medium. The basal medium was a nitrogen‐free, modified form of White's medium. Vegetative shoots were newly formed in the test tubes for concentrations of NO3‐N and NH4‐N that exceeded 56 mg L?1. However, no rhizome was formed at NH4‐N concentrations exceeding 28 mg L?1. The number of newly formed tubers decreased at an NH4‐N concentration of 28 mg L?1 and no tuber was formed at NH4‐N concentrations exceeding 56 mg L?1. In summary, although the presence of NO3‐N in the medium did not inhibit in vitro rhizome or tuber formation in E. arvense, the presence of NH4‐N in the medium exerted a strong inhibitory effect on the in vitro formation of both of these organs.  相似文献   

12.
The kinetics of inhibition of human and horse sera butyryl cholinesterases by solanaceous glycoalkaloids α-solanine, α-chaconine and tomatine has been studied by means of a potentiometric biosensor based on pH-sensitive field effect transistors (pH-FETs). Using acetyl- and butyryl choline as substrates, the optimal pH and the apparent kinetic parameters (Kmapp, Vmaxapp) of immobilized cholinesterases have been calculated in the absence of inhibitors. All studied glycoalkaloids were reversible inhibitors of both butyryl cholinesterases, and inhibited the horse and human immobilized enzymes in competitive and mixed modes, respectively. The affinity of each enzyme towards α-solanine, α-chaconine and tomatine has been estimated through calculation of apparent inhibition constants Kiapp and inhibition coefficients I50. An application of the butyryl cholinesterases studied in the biosensors for glycoalkaloids determination in the concentration range of 10−7 to 10−4 M has been discussed.  相似文献   

13.
A Ca-ATPase highly sensitive to DDT has been found in peripheral nerves of lobster, Homarus americanus. The observed I50 for this Ca-ATPase toward DDT is on the order of 10?9M and has a low temperature quotien. The ATPase seems to work over a wide range of ATP concentrations. It is stimulated by Ca2+ (optimum 0.1 mM) and shows sensitivity to Na+ (optimum 20 mM) and K+ (optimum 20 mM) ions. The fact that it is highly sensitive to ruthenium red (I50 = 10 μM) suggests that the enzyme is a Ca-ATPase and not a Mg-ATPase. Furthermore the enzyme is not a CaMg-ATPase, since the presence of Mg2+ along with Ca2+ ion is not required for its activity. DDT is found to inhibit the process of Ca2+ binding in the axonic membrane only in the presence of ATP. The evidence suggests the important role of the Ca-ATPase in regulating Ca2+ concentrations in the membrane. The possible significance of DDT inhibition of the ATPase is discussed.  相似文献   

14.
Trichoderma harzianum is an effective biocontrol agent against the devastating plant pathogen Rhizoctonia solani. Despite its wide application in agriculture, the mechanisms of biocontrol are not yet fully understood. Mycoparasitism and antibiosis are suggested, but may not be sole cause of disease reduction. In the present study, we investigated the role of oxidant-antioxidant metabolites in the root apoplast of sunflower challenged by R. solani in the presence/absence of T. harzianum NBRI-1055. Analysis of oxidative stress response revealed a reduction in hydroxyl radical concentration (•OH; 3.6 times) at 9 days after pathogen inoculation (dapi), superoxide anion radical concentration (O2•−; 4.1 times) at 8 dapi and hydrogen peroxide concentration (H2O2; 2.7 times) levels at 7 dapi in plants treated with spent maize-cob formulation of T. harzianum NBRI-1055 (MCFT), as compared to pathogen-inoculated plants. The protection afforded by the biocontrol agent was associated with the accumulation of the ROS gene network: the catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and ascorbate peroxidase (APx), maximum activity of CAT (11.0 times) was observed at 8 dapi, SOD (7.0 times) at 7 dapi, GPx (5.4 times) and APx (8.1 times) at 7 dapi in MCFT-treated plants challenged with the pathogen. This was further supported by the inhibition of lipid and protein oxidation in Trichoderma-inoculated plants. MCFT stimulated the accumulation of secondary metabolites of phenolic nature that increased up to five-fold and also exhibited strong antioxidant activity at 8 dapi, eventually leading to the systemic accumulation of phytoalexins. These results suggest that T. harzianum–mediated biocontrol may be related to alleviating R. solani-induced oxidative stress.  相似文献   

15.
Composition-concentration relationships between a series of C13/C14 polyoxyethylene primary alcohol (AE) surfactants and the foliar uptake enhancement of five model neutral organic compounds were examined in factorially designed experiments on wheat (Triticum aestivum L.) and field bean (Vicia faba L.) plants grown under controlled environment conditions. Model compounds were applied to leaves as c.0.2-μl droplets of 0.5 g litre?1 solutions in aqueous acetone in the absence or presence of surfactants at 0.2, 1 and 5g litre?1. Uptake of the highly water-soluble compound, methylglucose (log octanol-water partition coefficient (P) = - 3.0) was best enhanced by surfactants with high E (ethylene oxide) contents (AE15, AE20), whereas those of the lipophilic compounds, WL110547 (log P = 3.5) and permethrin (log P = 6.5), were increased more by surfactants of lower E contents, especially AE6. However, there was little difference between AE6, AE11, AE15 and AE20 in their ability to promote uptake of the two model compounds of intermediate polarity, phenylurea (log P = 0.8) and cyanazine (log P = 2.1). Absolute amounts of compound uptake were also influenced strongly by both surfactant concentration and plant species. Greatest amounts of uptake enhancement were often observed at high surfactant concentration (5 g litre?1) and on the waxy wheat leaves compared with the less waxy field bean leaves. The latter needed higher surfactant thresholds to produce significant improvements in uptake. Data from our experiments were used to construct a simple response surface model relating uptake enhancement to the E content of the surfactant added and to the physicochemical properties of the compound to be taken up. Qualitative predictions from this model might be useful in rationalising the design of agrochemical formulations.  相似文献   

16.
Cells were isolated from the developing leaves of Ipomoea aquatica (water spinach), a C3 plant, and three kinds of C4 plants, namely, Digitaria sanguinalis (NADP+-specific malate dehydrogenase type), Panicum miliaceum (NAD+-specific malic enzyme type), and Panicum texanum (phosphoenopyruvate carboxy kinase type), to study the effect of monuron on light-dependent 14CO2 fixation and oxygen evolution. Bundle sheath cells, except for those of D. sanguinalis, and mesophyll cells of all plants fixed approximately the same amount of 14CO2. Monuron, at the range used (2 to 10 × 10?7M), showed strong inhibition in the mesophyll cells of water spinach and in bundle sheath cells of P. miliaceum and P. texanum and moderate inhibition in the mesophyll cells of all C4 plants. In the bundle sheath cells of D. sanguinalis the low rate of 14CO2 fixation was stimulated to some extent by the addition of malate and ribose 5-phosphate. The I50 value was 6 × 10?7M for the sensitive cells. Monuron inhibited the oxygen evolution of all seven cell types and their I50 values varied between 3 × 10?7 to 6 × 10?7M. The differential response of isolated plant cells from different species to light-dependent CO2 fixation in the presence of monuron may also be involved in urea herbicide selectivity and undoubtedly is due to the differential photosynthetic pathways present nn them.  相似文献   

17.
Two Alisma plantago‐aquatica biotypes resistant to bensulfuron‐methyl were detected in rice paddy fields in Portugal’s Mondego (biotype T) and Tagus and Sorraia (biotype Q) River valleys. The fields had been treated with bensulfuron‐methyl‐based herbicide mixtures for 4–6 years. In order to characterize the resistant (R) biotypes, dose–response experiments, absorption and translocation assays, metabolism studies and acetolactate synthase (ALS) activity assays were performed. There were marked differences between R and susceptible (S) biotypes, with a resistance index (ED50R/S) of 500 and 6.25 for biotypes Q and T respectively. Cross‐resistance to azimsulfuron, cinosulfuron and ethoxysulfuron, but not to metsulfuron‐methyl, imazethapyr, bentazone, propanil and MCPA was demonstrated. No differences in the absorption and translocation of 14C‐bensulfuron‐methyl were found between the biotypes studied. Maximum absorption attained 1.12, 2.02 and 2.56 nmol g−1 dry weight after 96 h incubation with herbicide, for S, Q and T biotypes respectively. Most of the radioactivity taken up by the roots was translocated to shoots. Bensulfuron‐methyl metabolism in shoots was similar in all biotypes. The R biotypes displayed a higher level of ALS activity than the S biotype, both in the presence and absence of herbicide and the resistance indices (IC50R/S) were 20 197 and 10 for biotypes Q and T respectively. These data confirm for the first time that resistance to bensulfuron‐methyl in A. plantago‐aquatica is target‐site‐based. In practice, to control target site R biotypes, it would be preferable to use mixtures of ALS inhibitors with herbicides with other modes of action.  相似文献   

18.
The use of soil fumigants and fungicides to control soilborne pathogens is reduced due to awareness of their negative drawbacks. Long-term application of such agrochemicals negatively affects soil microbiota and reduces natural soil suppressiveness. We investigated long-term impacts of biochar and not-pyrogenic organic amendment (OAs: manure, alfalfa straw and glucose), on disease suppression compared with conventional management in three pathosystems: Fusarium oxysporum f. sp. lactucae (FOL)–lettuce, Rhizoctonia solani–tomato and Sclerotinia sclerotiorum–lettuce, by conditioning soil for 2 years. Soil analyses included pH, electrical conductivity, organic carbon, total nitrogen, C:N ratio, N-NO3−, N-NH4+, cation exchange capacity, available phosphorus, Ca2+, Mg2+, K+, Na+, fluorescein diacetate (FDA), and total and active limestone. Soil microbiota was characterized by combining BIOLOG EcoPlates with next-generation sequencing of 16S and 18S rRNA genes. Soil amended with OAs generally suppressed disease by S. sclerotiorum and FOL compared to fumigants and synthetic fertilizers. However, the incidence of R. solani infection was lower in soil treated with synthetic fertilizers than soil amended with OAs. EC, pH, C:N, N-NO3−, N-NH4+, FDA and BIOLOG were significantly correlated with disease, depending on pathosystem. Bacterial richness and diversity, presence of some genera like Acidobacteria, Chloracidobacteria, Solibacteres, Anaerolineae, Nitrospira and Deltaproteobacteria were negatively related to disease incidence of FOL and S. sclerotiorum, whereas damping-off caused by R. solani was negatively affected by the presence of Flavobacterium and Chitinofagha. Therefore, we concluded that long-term application of OAs can effectively improve soil suppressiveness and reduce disease incidence against root pathogens, although the effects vary considerably depending upon pathosystem.  相似文献   

19.
The effect of adjuvants on the performance of emulsifiable concentrate (EC) and wettable powder (WP) formulations of dimethomorph, a new systemic Oomycete fungicide, has been investigated using a two-day therapeutic (curative) assay with downy mildew (Plasmopara viticola, Berl. & de T.) on vines (Vitisvinifera L., cv. Cabernet Sauvignon) in glasshouse trials. The EC formulation had some therapeutic activity in this type of test. This activity was increased by the spray tank incorporation of 6 g litre−1 of either emulsifiable rape seed oil (‘Atplus’ 412) or emulsifiable paraffinic oil (‘Atplus’ 411F). However, these improvements in performance were overshadowed by those brought about by incorporation of 3 g litre−1 of a series of C13/C14 alcohol ethoxylates varying in ethylene oxide content from 5 to 20 moles:(‘Marlipal’ 34/6EO, 34/11EO, 34/20EO). Nearly complete fungal control was obtained in the presence of these adjuvants with a dimethomorph application rate of 25 g ha−1 compared with only around 90% control at 400 g ha−1 without adjuvants. The WP formulation was inactive in this therapeutic test but the presence of the adjuvants improved the performance of this formulation towards the high levels observed with the EC plus adjuvants, demonstrating that adjuvants could markedly influence the performance of solid, otherwise therapeutically inactive, dimethomorph formulations. Further trials examined other types of adjuvants (nonylphenol, alkylamine and silicone ethoxylates) but either they were no better than the alcohol ethoxylates or they induced unacceptable phytotoxicity. Trials with alcohol ethoxylates (‘Genapols’) from another source demonstrated activity equivalent to the ‘Marlipal’ surfactants. A two-factorial matrix experiment with ‘Genapol’ C050 showed that, under glasshouse conditions, >90% control could be obtained with the dimethomorph EC at 25 g AI ha−1 with 375 g ha−1 ‘Genapol’ C050. Applications of the WP formulation required slightly higher rates of either 50 g AI ha−1 plus 375 g ha−1 ‘Genapol’ C050 or 25 g AI ha−1 plus 750–1500 g ha−1 ‘Genapol’ C050. The overall conclusion was that alcohol ethoxylates varying in alkyl chain length from C12 to C18 and ethylene oxide content between 5 and 20 moles for the C12 surfactants and ∽15 moles for the C18 surfactants were effective adjuvants in promoting the therapeutic activity of dimethomorph formulationsagainst P. viticola on glasshouse-propagated vines.  相似文献   

20.
RH‐1965 is a new bleaching herbicide which causes newly developing leaf tissue to emerge devoid of photosynthetic pigments. Mode‐of‐action studies revealed that RH‐1965 inhibited the accumulation of both total chlorophyll and β‐carotene. Concomitantly, it induced the accumulation of the β‐carotene precursors, phytoene, phytofluene and, in particular, ξ‐carotene. Inhibition of chlorophyll accumulation by RH‐1965 is attributed to the photo‐oxidative destruction of chlorophyll in the absence of β‐carotene because RH‐1965 blocked chlorophyll accumulation to a greater extent under high light (50–330 µE m−2 s−1) than under low light (0.8 µE m−2 s−1) conditions. Radish (Raphanus sativus L) and barnyardgrass (Echinochloa crus‐galli (L) Beauv) were very senstive to RH‐1965. Under high light (330 µE m−2 s−1), the I50 values for inhibition of chlorophyll accumulation were 0.10 and 0.15 µM , respectively. Wheat (Triticum aestivus L), on the other hand, was much less sensitive to RH‐1965 (I50 = 1.4 µM ). It is concluded that the mode of action of RH‐1965 involves the inhibition of ξ‐carotene desaturation. © 2000 Society of Chemical Industry  相似文献   

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