Natural diterpene β-lactone derivative as photosystem II inhibitor on spinach chloroplasts

α,7β-Dihydroxyvouacapan-17β-oic acid (1) was isolated from Pterodon polygalaeflorus Benth. Then, (1) was modified to obtain 6α-hydroxyvouacapan-7β,17β-lactone (2). Inhibition properties of both (1) and (2) were evaluated in spinach chloroplasts. Only compound (2) inhibited non-cyclic electron transport and ATP synthesis, i.e., (2) behaved as a Hill reaction inhibitor. Compound (2) did not affect photosystem I (PSI) activity but it did inhibit electron flow through PSII. Analysis of the partial PSII reactions from water to DCPIP_ox, water to silicomolybdate, and diphenylcarbazide to DCPIP_ox allowed locating inhibition sites at (i) the oxygen-evolving complex (OEC) and (ii) the redox enzymes of the electron transport chain, in the span of P₆₈₀ to Q_A. Chlorophyll a fluorescence measurements confirmed the action site for (2).     

Pesticides-induced depression of photosynthesis was alleviated by 24-epibrassinolide pretreatment in Cucumis sativus L

The phytotoxicities of nine pesticides (paraquat, fluazifop-p-butyl, haloxyfop, flusilazole, cuproxat, cyazofamid, imidacloprid, chlorpyrifos, and abamectin) at practical dosages on photosynthesis were investigated in cucumber (Cucumis sativus L. cv. Jinyan No. 4) by gas exchange and chlorophyll fluorescent measurements. Plants treated with paraquat showed the severest phytotoxic symptom with the highest reduction in net photosynthetic rate (Pn), while other pesticides except flusilazole inhibited Pn to various degrees. The inhibition of Pn by cuproxat was accompanied by declines both in stomatal conductance (Gs) and intercellular CO₂ concentration (Ci), whereas decreased Pn for the cyazofamid was associated with increased Ci. For other 6 pesticides, however, inhibition of Pn was accompanied by decrease in Gs, while Ci was increased or unaffected. Paraquat almost completely inhibited the maximal quantum efficiency of PSII (F_v/F_m), while other pesticides had no significant effect on F_v/F_m. Quantum efficiency of PSII (Φ_PSII) was significantly reduced by paraquat, fluazifop-p-butyl, and chlorpyrifos and the reduction was mostly attributed to decrease in photochemical quenching coefficient (qP). In comparison, Φ_PSII was not significantly affected by haloxyfop, flusilazole, cyazofamid, imidacloprid, and abamectin. Non-photochemical quenching (NPQ) was suppressed by paraquat and haloxyfop, while apparent upregulation was evident after exposure to other pesticides. Interestedly, inhibitions of Pn were alleviated by 24-epibrassinolide (EBR) pretreatment, as for the pesticides examined in this study except paraquat and flusilazole. EBR pretreatment also increased Φ_PSII and qP. It is likely that EBR enhanced the resistance of cucumber seedlings to pesticides by increasing CO₂ assimilation capacity and activities of antioxidant enzymes.     

Extracellular ATP functions in alleviating the decrease of PSII photochemistry caused by the infection of Xanthomonas campestris pv. phaseoli

Extracellular ATP (eATP) can function as a signalling molecule to regulate a wide range of cellular processes. This present work investigated the role of eATP in mediating the change of PSII (photosystem II) photochemistry of the tissues of Phaseolus vulgaris leaves infected with Xanthomonas campestris pv. phaseoli (Xcp). Infection of the leaves with Xcp caused a significant decrease in the the PSII maximal photochemical efficiency (F_v/F_m), the maximum quantum efficiency of PSII photochemistry at illumination (F_v′/F_m′), the PSII operating efficiency (Φ_PSII), the rate of non‐cyclic electron transport through PSII (ETR), photochemical quenching (qP), and eATP level in the tissues of the infected leaves. At the same time, the levels of non‐photochemical quenching (qN) and the quantum yield of regulated energy dissipation of PSII (Y(NPQ)) were significantly increased. Application of exogenous ATP at 0·2 mm to uninfected leaves had no significant effect on any of the chlorophyll fluorescence parameters being measured. However, in the tissues of infected leaves, the application of exogenous ATP alleviated the decreases of the F_v/F_m, F_v′/F_m′, Φ_PSII, ETR, qP and eATP level, and also abolished the increases of qN and Y(NPQ). These results suggest that the change of PSII photochemistry by pathogen infection could be mediated by eATP.     

Effect of herbicide clomazone on photosynthetic processes in primary barley (Hordeum vulgare L.) leaves

The effect of pre-emergently applied herbicide clomazone on the photosynthetic apparatus of primary barley leaves (Hordeum vulgare L.) was studied. Clomazone application caused a reduction in chlorophyll (a+b) and carotenoid levels that was accompanied by a decline in the content of light harvesting complexes as judged from the increasing chlorophyll a/b ratio. The pigment reduction also resulted in changes in 77 K chlorophyll fluorescence emission spectra indicating lower chlorophyll (Chl) fluorescence reabsorption and absence of the long-wavelength emission forms of photosystem I. The maximal photochemical yield of photosystem II (PSII) and the reoxidation kinetics of the primary quinone acceptor Q_A⁻ were not significantly influenced by clomazone. A higher initial slope of Chl fluorescence rise in the Chl fluorescence induction kinetic indicated an increased delivery of excitations to PSII. Simultaneously, analysis of the Chl fluorescence quenching revealed that clomazone reduced function of the electron transport chain behind PSII. The decrease in the saturation rates of CO₂ assimilation paralleled the decrease of the Chl content and has been suggested to be caused by a suppressed number of the electron transport chains in the thylakoid membranes or by their decreased functionality. The obtained results are discussed in view of physiological similarity of the clomazone effect with changes of photosynthetic apparatus during photoadaptation.     

啶虫脒和阿维菌素在4种不同类型土壤中的吸附及迁移

采用薄层层析和平衡振荡法,分别测定了啶虫脒和阿维菌素在紫色土、砖红土、黄壤土和黑土4种不同类型土壤中的迁移率(Rf )和吸附常数(Kd),比较了2种农药在单用及混用下迁移和吸附行为的差异。结果表明:2种农药在单用及混用下的迁移行为几乎不存在差异,在4种土壤中的Rf 值大小顺序均为:黄壤土>紫色土>黑土>砖红土;2种农药的吸附过程均符合经典的Freundlich模型,混用时阿维菌素对啶虫脒的吸附无影响,但啶虫脒的存在会减少土壤对阿维菌素的吸附,表现为竞争吸附作用。     

Chlorophyll fluorescence for visualizing the spatial and temporal spread of Phytophthora alni subsp. alni in alder bark tissue

The impact of alder Phytophthora (Phytophthora alni subsp. alni) on corticular photosynthetic metabolism was explored via measurements of chlorophyll fluorescence. Stem inoculation induced a sharp reduction of maximum (F_v/F_m) and effective quantum yield of PSII (). Observations of the axial and radial spread of the pathogen revealed that near to the point of inoculation and in the whole centre of the stem lesion F_v/F_m and of the cortex chlorenchyma decreased to almost zero, indicating tissue necrosis. Low values of F_v/F_m and were also found in some presymptomatic regions beyond the visible stem lesion. In contrast, substantial photosynthetic activity was found in uninvaded parts of the inoculated trees and in the control. These stem parts showed a marked light‐adapted quantum efficiency of PSII as well as marked electron transport rates in their bark tissues. Thus, corticular photosynthesis stayed unaffected in these stem parts supporting stem carbon balance. Chlorophyll fluorescence measurements in the field illustrated that stem infection with P. alni subsp. alni and the effect on the bark tissues is not only highly heterogeneous but also underlies very quick temporal changes, due to a rapid destruction of the photosynthetic apparatus. The results show that chlorophyll fluorescence measurements and fluorescence imaging are useful indicators of tissue infection caused by Phytophthora infection of bark tissues. Chlorophyll fluorescence measurements can be used to map and visualize the spatial as well as temporal spread of bark pathogens and can give a first indication of invasion of the host tissue beyond the visible lesion.     

Tolerance of triazine-resistant and susceptible biotypes of three weeds to heat stress: a fluorescence study

The photosynthetic performance of Solarium nigrum L., Poa annua L. and Chenopodium album L. resistant to triazines was investigated in order to determine whether the alteration of the 32-kD protein of photosystem (PS) II changed the ability to oxidize the PSII primary quinone acceptor Q_A. The effect of heat stress on the photochemistry of the resistant biotypes and the susceptible biotypes was also compared. The weeds were screened with the in-vivo modulated chlorophyll fluorescence device to measure the photochemical component of fluorescence quenching (q_Q), which provided semi-quantitative information on the redox state of Q_A. At 25°C, an increase in the amplitude of the parameter 1-q_Q, which reflected the reduced state of Q_A, was observed in all resistant biotypes, compared to the susceptible wild biotypes. This was attributable to a shift in the equilibrium between Q_A^? and Q_B (the PSII secondary quinone acceptor) in favour of Q_A. A heat stress of 35°C did not increase the level of reduced Q_A, except in the resistant biotypes of Poa annua. The photochemical activity of the two types of leaves exposed to increasingly high temperatures (25–65°C) indicated that quinone oxidation was more affected by heat stress in mutant resistant biotypes than in the susceptible biotypes. The quinone reoxidation was nullified at 60, 56 and 60°C, respectively, for susceptible biotypes of Solatium nigrum, Poa annua and Chenopodium album, and at 56, 48 and 54°C, respectively, for the three resistant biotypes. Heat also induced changes in the dark fluorescence F₀, an indicator of the heat sensitivity of the light-harvesting chlorophyll protein complex of PSII (LHCPII). The temperature dependence (25–70°C) of this fluorescence parameter confirmed the higher susceptibility of heat-treated resistant leaves. Indeed, the temperatures of the peak of F₀ (Tp) were 60, 55 and 62°C for susceptible Solanum nigrum, Poa annua and Chenopodium album, respectively. The Tp values for the three resistant biotypes were 55, 48 and 57°C, respectively. It is concluded that heat tolerance is related to differences in the organization of the chlorophyll antennae (LHCPII) between the two biotypes. Tolerance de biotypes sensibles et resistants aux triazines de 3 adventices au stress de la chaleur: une étude de fluorescence Les rendements photosynthétiques de Solanum nigrum L., Poa annua L. et Chenopodium album L. resistant aux triazines ont étéétudiés en vue de déterminer dans quelle mesure l'altération de la protéïne 32 kD du photosystème (PS) II, affecte la capacité d'oxyder l'accepteur quinonique primaire de PS II. Q_A L'influence d'un stress de chaleur sur la photochimie de biotypes résistants et de biotypes sensibles a été comparée. Les mauvaises herbes ont été triées au moyen de la fluorescence de la chlorophylle in vivo, pour mesurer la composante photochimique de réduction de la fluorescence (q_Q) qui donne une information semi quantitative de l'état redox de Q_A. A 25 °C, une augmentation dans l'amplitude du paramètre 1-qQ, qui reflète l'état réduit de Q_A a été observée chez les biotypes resistants encomparaison des biotypes sauvages sensibles. Ceci a été attribuéà une modification dans l'équilibre entre Q^?_A et Q_B (l'accepteur quinonique secondaire PS II), en faveur de Q_A. Un stress thermique de 35°C n'a pas augmenté le niveau de Q_A réduit, sauf chez le biotype résistant de Poa annua. L'activité photochimique des feuilles des 2 types exposées à des hautes températures croissantes (25 à 65°C) a montré que l'oxydation de la quinone était plus affectée par le stress thermique chez les biotypes mutants résistants que chez les biotypes sensibles. La réoxydation de la quinone était annulée à 60, 56 et 60°C respectivement pour les biotypes sensibles de Solatium nigrum, Poa annua et Chenopodium album et à 56, 48 et 54°C respectivement pour les 3 biotypes résistants. La chaleur a également entrainé des changements dans la fluorescence F₀, un indicateur de la sensibilitéà la chaleur du complexe collecteur de lumière du PS II (LHCP II). La dépendance avec la température (25–70°C) de ce paramètre de fluorescence a confirmé la plus grande sensibilité des feuilles résistantes soumises à la chaleur. En effet, les températures du pic de F_o (Tp) étaient de 60, 55 et 62°C respectivement, pour les biotypes sensibles de Solanum nigrum, Poa annua et Chenopodium album. Les valeurs Tp pour les 3 biotypes résistants étaient respectivement de 55, 48 et 57°C. Il est conclu que la tolérance à la chaleur est liée aux différences dans l'organisation des antennes chlorophylliennes (LHC P II) entre les 2 biotypes. Hitzetoleranz Triazin-resistenter und -empfindlicher Biotypen von drei Unkrautarten Die photosynthetische Leistung Triazin-resistenter Biotypen von Solanum nigrum L., Poa annua L. und Chenopodium album L. wurde dahingehend untersucht, ob eine Veränderung des 32-kD-Eiweisses des Pigmentsystems II (PII) die Fähigkeit änderte, den primären Quinon-Akzeptor Q_A des PII zu oxidieren. Auch die Wirkung einer Hitzebehandlung auf die photochemischen Reaktionen resistenter und empfindlicher Biotypen wurde verglichen. Die Unkräuter wurden in vivo mit einem Chlorophyll-Fluorimeter gescreent, um die photochemische Komponente der Fluoreszenz-Auslösung (q_Q) zu messen, die eine semiquantitative Information über den Redox-Zustand des Q_A lieferte. Die Amplitude des Parameters l-q_Q, der den reduzierten Zustand des Q_A widerspiegelte, nahm bei 25°C bei allen resistenten Biotypen im Vergleich zu den empfindlichen zu. Dies konnte einer Verschiebung des Gleichgewichts zwischen Q^?_A und Q_B (dem sekundären Quinon-Akzeptor Q_A des PII) zugunsten des Q_A zugeordnet werden. Eine Hitzebehandlung mit 35°C erhöhte den reduzierten Q_A nicht, außer bei resistenten Biotypen von Poa annua. Die photochemische Aktivität von Blättern der beiden Typen, die steigenden Temperaturen von 25 bis 65°C unterworden wurden, zeigte, daß die Quinon-Oxidation bei den resitenten Biotypen durch den Hitzestreß stärker beeinflußt wurde als bei den empfindlichen. Die Quinon-Reoxidation wurde bei den empfindlichen Biotypen von Solanum nigrum, Poa annua und Chenopodium album bei 60, 56 bzw. 60°C aufgehoben, bei den resistenten bei 56, 48 bzw. 54°C. Hitze führte auch zu Änderungen der Dunkel-Fluoreszenz F_o, einem Indikator der Hitzeempfindlichkeit des lichtabsorbierenden Chlorophyll-Eiweißkomplexes des PII (LHCPII). Die Temperaturabhängigkeit dieses Fluoreszenz-Parameters bei 25 bis 70°C bestätigte die höhere Empfindlichkeit hitzebehandelter Blätter resistenter Pflanzen. So waren F_o-Peaks bei empfindlichen Solanum nigrum, Poa annua und Chenopodium album bei 60, 55 bzw. 62°C, bei resistenten bei 55, 48 bzw. 57°C festzustellen. Daraus wurde geschlossen, daß die Hitzetoleranz auf Unterschieden im Aufbau des lichtabsorbierenden Pigmentsystems LHCPII der beiden Biotypen beruht.     

Uncoupling and inhibition properties of 3,4-seco-friedelan-3-oic acid isolated from Maytenus imbricata

3,4-Seco-friedelan-3-oic acid was isolated from Maytenus imbricata (Celastraceae). At low concentrations it inhibited non-cyclic electron transport and ATP synthesis in spinach chloroplasts, i.e., it behaved as a Hill reaction inhibitor, and at high concentrations it acts as an uncoupler by enhancing uncoupled electron transport and Mg²⁺-ATPase activity. 3,4-Seco-friedelan-3-oic acid did not inhibit PSII electron transport from DPC to DCPIP_ox and photosystem I activity, but it enhanced from TMQH₂ to MV, corroborating its action as uncoupler. It inhibits electron flow through PSII from water to sodium silicomolybdate. The whole results indicate that the 3,4-seco-friedelan-3-oic acid target is at the OEC complex enzyme, the donor side of PSII. The fluorescence decay data shows the formation of the K-band, which match this result, acting as inhibitor at the donor side of PSII and it as an uncoupler.     

Inhibition of photosystem II in spinach chloroplasts by trachyloban-19-oic acid

The effect of trachyloban-19-oic acid isolated from Iostephane heterophylla (Asteraceae), was investigated on several photosynthetic activities in spinach thylakoids. The results indicated that this compound inhibited ATP synthesis and uncoupled electron transport, as well as basal and phosphorylating electron flow. Therefore, trachyloban-19-oic acid acts as Hill reaction inhibitor. This compound did not affect photosystem I activity but inhibited uncoupled photosystem II electron flow from H₂O to DCPIP, and has not effect on electron flow from H₂O to SiMo, indicating that the site of inhibition of this compound is at the level of Q_A-Q_B. Chlorophyll a fluorescence measurements confirm the behavior of this diterpene as Q_A-Q_B inhibitor, and in the other hand, this results indicate that a perturbation in the thylakoid membranes at the level of LHC II occurs.     

Pre-symptomatic detection of <Emphasis Type="Italic">Plasmopara viticola</Emphasis> infection in grapevine leaves using chlorophyll fluorescence imaging

Plasmopara viticola is an economically important pathogen of grapevine. Early detection of P. viticola infection can lead to improved fungicide treatment. Our study aimed to determine whether chlorophyll fluorescence (Chl-F) imaging can be used to reveal early stages of P. viticola infection under conditions similar to those occurring in commercial vineyards. Maximum (F_V/F_M) and effective quantum yield of photosystem II (Φ_PSII) were identified as the most sensitive reporters of the infection. Heterogeneous distribution of F_V/F_M and Φ_PSII in artificially inoculated leaves was associated with the presence of the developing mycelium 3 days before the occurrence of visible symptoms and 5 days before the release of spores. Significant changes of F_V/F_M and Φ_PSII were spatially coincident with localised spots of inoculation across the leaf lamina. Reduction of F_V/F_M was restricted to the leaf area that later yielded sporulation, while the area with significantly lower Φ_PSII was larger and probably reflected the leaf parts in which photosynthesis was impaired. Our results indicate that Chl-F can be used for the early detection of P. viticola infection. Because P. viticola does not expand systemically in the host tissues and the effects of infection are localised, Chl-F imaging at high resolution is necessary to reveal the disease in the field.     

Furanoditerpene ester and thiocarbonyldioxy derivatives inhibit photosynthesis

6α,7β-Dihydroxyvouacapan-17β-oic acid (1) and methyl 6α,7β-dihydroxyvouacapan-17β-oate (8) were isolated from Pterodon polygalaeflorus Benth. 1 was modified to obtain 6α-hydroxyvouacapan-7-β,17β lactone (2). Then, 6-oxovouacapan-7β,17β lactone (3) was obtained from 2. The furanoditerpene ester derivatives: propyl 7β-hydroxy-6-oxovouacapan-17β-oate (4), butyl 7β-hydroxy-6-oxovouacapan-17β-oate (5), 2-methoxyethyl 7β-hydroxy-6-oxovouacapan-17β-oate (6) and 3-methylbut-2-enyl 7β-hydroxy-6-oxovouacapan-17β-oate (7) were synthesized from (3) and methyl 6α,7β-thiocarbonyldioxyvouacapan-17β-oate (9) was obtained from (8). In this work, the lactone ester derivatives 4-7 and 9 were tested on photosynthetic activities in an attempt to search for new compounds as potential herbicide agents that affect photosynthesis. All compounds inhibited ATP synthesis and electron flow from water to MV, therefore, they act as Hill reaction inhibitors, being 4- to 9-fold more potent than 2 and 3 as inhibitors of ATP synthesis. Their interaction site was located at PSII in a similar way to diuron. Furthermore, furanoditerpene esters 6 and 7 act as uncouplers, and were corroborated by enhancement of the light-activated Mg²⁺-ATPase, while 5 act as an energy transfer inhibitor. Finally 5-7 behave as herbicides, since they inhibit the biomass production of weeds assay.     

Longevity of a mixture of acetamiprid and bifenthrin (Transport(TM) ) at the termiticidal application rate

BACKGROUND: The 30 month longevity, mobility and insecticidal activity of a combination of acetamiprid and bifenthrin currently marketed in the United States for the prevention of termite infestation in buildings was investigated in greenhouse and laboratory studies. RESULTS: Acetamiprid dissipated to below the limit of detection within 7 months of application, while bifenthrin remained in the soil at levels sufficient to kill termites for the duration of the study. Acetamiprid was detected in decreasing amounts in eluates of treated soil from months 1 to 4, while no bifenthrin was detected in eluates at any time. The treated soil remained toxic to termites for the 30 month duration of the study. Two indices of synergy between technical‐grade acetamiprid and bifenthrin demonstrated that it is unlikely that there would be any synergism between the two active ingredients in the field. The presence of vegetation did not have a significant effect on the longevity of bifenthrin, except at intermediate times, where residues in the treated soil were higher in vegetated plots, depending on depth and time. CONCLUSIONS: Acetamiprid has a short residual time in soil, and this formulation's effectiveness beyond about 7 months against subterranean termites is due to the bifenthrin content. Copyright © 2011 Society of Chemical Industry     

常用杀虫剂对异色瓢虫的毒力及其保护酶的影响

为明确杀虫剂对异色瓢虫Harmonia axyridis(Pallas)幼虫、成虫的毒力及其体内保护酶的影响,采用喷雾法测定了7种杀虫剂对异色瓢虫3龄幼虫和成虫的毒力,同时测定了3种杀虫剂对3龄幼虫和成虫体内超氧化物歧化酶(superoxide dismutase)、过氧化物酶(peroxidase)和过氧化氢酶(catalase)活性的影响。结果显示:7种杀虫剂对3龄幼虫的毒力大小为阿维菌素、啶虫脒吡虫啉、虫酰肼哒螨灵噻嗪酮吡蚜酮,对成虫的毒力大小为阿维菌素、啶虫脒虫酰肼、吡虫啉哒螨灵噻嗪酮吡蚜酮,吡蚜酮对异色瓢虫最安全。亚致死浓度LC10药剂可促进保护酶活性的提高,但随着浓度提高和处理时间增长,3种酶的活性总体呈逐渐下降趋势,表明低浓度的杀虫剂对异色瓢虫体内酶活性存在一定的不利影响。     

<Emphasis Type="Italic">Alternaria</Emphasis> species associated with early blight epidemics on tomato and other <Emphasis Type="Italic">Solanaceae</Emphasis> crops in northwestern Algeria

Clubroot, caused by the protozoan parasite Plasmodiophora brassicae Woronin, is one of the most damaging diseases of Brassica napus worldwide. Resistant plant material is valuable for cultivation in all areas of high incidence of the disease and intensive growth of oilseed rape. We have evaluated clubroot resistance, plant morphology and seed quality in 15 lines of an F₄ generation and selected six lines of F₅ generation of interspecific hybrids obtained from a cross between a male sterile line of B. napus ‘MS8’, selected from resynthesized oilseed rape (B. rapa ssp. chinensis × B. oleracea var. gemmifera) and an ecotype of B. rapa ssp. pekinensis. Clubroot resistance was evaluated using a bioassay with P₁-P₅ pathotypes of P. brassicae (according to the classification of Somé et al. 1996). The resistance to the pathotype P₁ was successfully fixed in the F₅ generation, and improved in some lines in respect to the pathotypes P₂-P₄. The resistance to P₁ and the other tested pathotypes was not linked. Characterization of plant material included recent techniques of FISH and BAC-FISH with a special focus on the analysis of ribosomal DNA (rDNA) of selected individuals. Two hybrid lines combined high levels of resistance with appropriate plant morphology, good seed quality traits and a stable chromosome number and arrangement. Recent techniques of ‘chromosome painting’ provided good insight into chromosome organization in the hybrids obtained, and offered opportunities of further improvement of the breeding process.     

Ultra-structural changes in the integument induced by the use of three of six forms of allylisothiocyanate tested against Plutella xylostella and Pieris rapae larvae

The insecticidal activity of four forms of Hong Jing (HJ) allylisothiocyanate (AITC), AITC + cypermethrin (HJ_A, HJ_B, and HJ_C) with ratio of (1:1, 4:1, and 2:1), pure AITC (HJ_D), and two forms of Hong Du (HD) AITC, AITC + chlorpyrifos (HD_A and HD_B) with ratio of (2:1 and 2:1), respectively, were studied on the major cruciferous insect larvae Plutella xylostella (L.) and Pieris rapae (L.) by combining both spraying and dipping methods. The P. rapae was more susceptible than P. xylostella larvae. The LC₅₀ values 72 h after treatment of AITC forms (HJ_B, HJ_A, HJ_C, HJ_D, HD_B, and HD_A) on the P. rapae were; 0.07, 0.08, 0.16, 0.83, 0.26, 1.08 gL⁻¹, and 0.69, 0.26, 5.45, 0.93, 3.01, 5.98 gL⁻¹ on the P. xylostella, respectively. The toxicity of some of the AITC forms was very close to or better than that of the commercial contact insecticides such as chlorpyrifos (LC₅₀ = 0.03 and 0.04 gL⁻¹ on P. rapae and P. xylostella, respectively), and cypermethrin (0.65 and 0.78 gL⁻¹, respectively, against P. rapae and P. xylostella). The ultrastructural studies on the integument of the third larval instar of P. xylostella treated by sub-lethal concentration (LC₂₀) of HJ_B, HJ_D, and HD_B were carried out by using transmission electron microscope. The more pronounced alterations in the hypodermis and mitochondria cells. They exhibited changes in all treated samples. The hypodermis was almost completely destroyed, and the mitochondria exhibited morphological alterations, represented by enlargement, matrix rarefaction and vacuolization of the mitochondria matrix, quantity of cristae reduced, and density electron matrix lessened. These AITC forms have potential as contact insecticides, and the ultra structural observations confirm the insecticidal efficiency of different AITC forms on P. rapae and P. xylostella.     

Insecticidal activity and mode of action of novel nicotinoids synthesized by new acylpyridinium salt chemistry and directed lithiation

Novel acylpyridinium salt chemistry and directed lithiation methodology was developed to add for the first time substitutions directly to the phenylpyridine heterocyclic ring of nicotine. A variety of 3-(1-methylpyrrolidin-2-yl)-4-(alkyl, aromatic, heterocyclic and silanyl) and -N-alkyl pyridines were synthesized (compounds 1-9). In vial tests with the green peach aphid, Myzus persicae, compounds 1-4 were 1.1, 1.8, 2.3 and 1.9×, respectively, more active than nicotine and 64, 40, 31 and 38×, respectively, less active than acetamiprid. Against the western flower thrips, Frankliniella occidentalis, 1-4 were 1.4, 2.1, 2.0 and 1.6×, respectively, more active than nicotine and 9, 6, 6 and 8×, respectively, less active than acetamiprid. For the cotton aphid, Aphis gossypii, the activity of 1-9 was similar to nicotine. Compounds 7 and 9 when incorporated into artificial diet produced low mortality for larvae of the beet armyworm, Spodoptera exigua, but were not active against the corn earworm, Helicoverpa zea. When 1-4 and 6-9 were injected into larvae of the beet armyworm, a variety of symptoms similar to acetamiprid were observed which included tremors, uncoordinated movement, diuresis, paralysis and death. In addition, imidacloprid-binding to membranes from the house fly head, Musca domestica, was inhibited by compounds 1-9, when using a concentration range of 1-100 μM. These studies demonstrate that our new chemistry enhances the insecticidal activity of nicotine with an apparent mode of action as an acetylcholine agonist.     

Effects of fungicides JS399-19, azoxystrobin, tebuconazloe, and carbendazim on the physiological and biochemical indices and grain yield of winter wheat

The impact of four modern fungicides JS399-19 (2-cyano-3-amino-3-phenylancryic acetate) (novel fungicide), azoxystrobin (a strobilurin), tebuconazole (a triazole) and carbendazim (a benzimidazole), applied as foliar spray at the recommended field rate, on the physiology and biochemistry of the senescence process and grain yield was studied in winter wheat (Triticum aestivum L. cv. ‘Nannong No. 9918’) under natural environmental conditions. Fungicide treatments to wheat plants at growth stage [ZGS] 57 (3/4 of head emerged) significantly increased the chlorophyll (CHL) and soluble protein (SP) content and decreased the malondialdehyde (MDA) content and electrolyte leakage. Additionally, activities of the antioxidative enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in flag leaves of the fungicide-treated plants were also higher than that in untreated plants. These coincided with elevated levels of H₂O₂ and reduced level of in the fungicide-treated plants. The results suggested that the fungicide-induced delay of senescence was due to an enhanced antioxidant enzyme activity protecting the plants from harmful active oxygen species (AOS). Because all fungicides can induce the delay of wheat senescence, fungicide-treated wheat shown higher grain yield than untreated wheat. Of all tested fungicides, JS399-19, azoxystrobin and tebuconazole showed similar effects on delaying senescence of wheat and enhancing the grain yield of wheat, but JS399-19 was more efficient in general.