Growth and physiological responses of freshwater green alga Selenastrum capricornutum to allelochemical ethyl 2-methyl acetoacetate (EMA) under different initial algal densities

Most natural algicides including macrophytic allelochemicals are known to selectively inhibit algal growth. The investigations on the modes of action about the species-specific algicides are little. In this study, the effects of allelochemical ethyl 2-methyl acetoacetate (EMA) identified from reed (Phragmites communis) on the growth, physiological, and biochemical processes of green alga Selenastrum capricornutum were investigated. The results showed that EMA had multiple effects on the growth of S. capricornutum under different initial algal densities (IADs). The algal growth was inhibited by EMA at low IADs, but stimulated at high IADs. Further, the potential modes of action of EMA on S. capricornutum were explored from ultrastructure, metabolic activity, reactive oxygen species level, and lipid peroxidation to trace the microenvironment changes in the algal cells. Damage in cell structure occurred at low IAD, but cells were well developed with increased metabolic activity at high IAD. The reactive oxygen species (ROS) levels were increased under both conditions. The increase of ROS level was acute at low IAD but slow at high IAD. EMA caused significant lipid peroxidation, i.e. oxidative damage on membrane lipids at low IAD but not at high IAD. Based on these results, the initial algal density is considered an important factor to influence algal growth and physiological and biochemical responses to EMA, the effects of EMA on S. capricornutum may be “hormesis-like”, and different ROS increase ratio may be directly related with different responses of S. capricornutum to EMA.     

Effect of waterborne benomyl on the hematological and antioxidant parameters of the Nile tilapia, Oreochromis niloticus

The present study was conducted to determine the 96 h-LC₅₀ of benomyl to the Nile tilapia, Oreochromis niloticus and to investigate the biochemical or hematological indices of blood and the alterations in the antioxidant enzymes of this fish in response to sublethal concentrations of benomyl. Fish weighing 71.61 ± 12.05 g were used in this study; they were subjected to fasting for 4 weeks before treatment. An aqueous solution of benomyl (0, 0.5, 1, 2, 4, 8, and 16 mg L⁻¹) was administered for 96 h to determine the LC₅₀. The 96 h-LC₅₀ value of benomyl was 4.39 (3.23-5.60) mg L⁻¹ in the present study. For 5 weeks, the aqueous solution of benomyl (0, 100, 200, and 400 μg L⁻¹) was administered to investigate its effect on the hematological parameters and antioxidant enzymes. The predominant hematological findings in fish exposed to benomyl were as follows: no significant change in the Hb (g dL⁻¹) level, MCV (μm³), MCH (pg) and MCHC (%) as compared to the control. Benomyl exposure led to greater increases in the GPT, GOT (Karmen-unit), LDH (Wroblewski unit), total cholesterol, Fe, and Ca (mg dL⁻¹) values, whereas the levels of ALP (KA unit), total protein, triglyceride, albumin, and Mg (mg dL⁻¹) did not increase. Benomyl increased the in vivo HSI (%), GST (nmol min⁻¹ mg protein⁻¹), and SOD (U mg protein⁻¹) values in the fish livers in the test group, unlike those in the control group for 5 weeks. At concentrations higher than 100 μg L⁻¹, benomyl affected the GST and SOD levels of Nile tilapia in a dose- and time-dependent manner. The present findings suggest that the in vivo hepatotoxicity associated with benomyl may, in part, result from the hematological index, and antioxidants may provide limited protection against benomyl toxicity.     

Biochemical effects of acute phoxim administration on antioxidant system and acetylcholinesterase in Oxya chinensis (Thunberg) (Orthoptera: Acrididae)

The study was undertaken to evaluate the effects of different concentrations of phoxim on acetylcholinesterase (AChE) and esterase (EST) activities, and antioxidant system after topical application to Oxya chinensis. The results showed that phoxim inhibited AChE activity, and did not cause significant changes in the EST activity and the levels of malondialdehyde (MDA) and reduced glutathione (GSH). After phoxim administration, superoxide (SOD) and catalase (CAT) activities showed a biphasic response with an initial increase followed by a decline in their activities. Glutathione reductase (GR) and glutathione peroxidase (GPx) activities were inhibited in comparison with the control. Glutathione S-transferase (GST) activity showed irregular changes. Its activity increased significantly at the concentrations of 0.06 and 0.12 μg/μL and decreased at the concentrations of 0.09 and 0.24 μg/μL compared with the control. Changes in SOD, CAT, GST, GPx, and GR activities indicated that phoxim caused oxidative damage in O. chinensis. However, no significant changes in MDA content suggested that these enzymes played important roles in scavenging the oxidative free radicals induced by phoxim in O. chinensis. The formation of oxygen free radicals might be a factor in the toxicity of phoxim.     

Activation of paraquat in the earthworm Allolobophora chlorotica is mediated by NAD(P)H-cytochrome c reductase activities

This study reports that earthworms, Allolobophora chlorotica, are capable of biotransforming paraquat, a toxic herbicide, resulting in the formation of reactive oxygen species (ROS). We found that in earthworms the reduction of paraquat is mediated by NADPH- and NADH-cytochrome c reductase activities. The formation of superoxide anion (O₂⁻) from the incubation of paraquat with the earthworm extracts was demonstrated by using both Cypridina luciferin analog (CLA) chemiluminescence and the SOD-inhibitable cytochrome c reduction reaction. In addition, in vivo exposure of earthworms to paraquat in solution (24 and 48 h) was performed to investigate whether or not the herbicide affects the levels of the NAD(P)H-cytochrome c reductase activities. Although in vitro NADPH-cytochrome c reductase reduces paraquat more easily than the NADH-dependent activity, after the in vivo exposure an increase of NADH-cytochrome c reductase activity(s) by 12% compared to control values was observed, whereas NADPH-cytochrome c reductase activity was not affected. Xanthine oxidase (XO) is an enzyme implicated in paraquat toxicity, however, no XO was detected in earthworm extracts nor hypoxanthine was a source of electrons for the herbicide reduction. For comparative reasons menadione, a redox cycling quinone, was also incubated with the earthworm extracts. It was found that the incubation of menadione with earthworm extracts formed about two times more (O₂⁻) than with paraquat. It is concluded that the exposure of paraquat to earthworms could elicit radical formation and consequently toxic effects via oxidative stress-mediated mechanisms. The reduction of paraquat by the reductases leads to the formation of paraquat radical, which reacts with molecular oxygen, accounting for the formation of superoxide anion. Further studies are required to conclude that the observed increase of NADH-cytochrome c reductase activity(s) should be used as a biomarker for paraquat exposure in earthworms.     

Elevated antioxidant response and induction of tau-class glutathione S-transferase after glyphosate treatment in Vigna radiata (L.) Wilczek

Glyphosate (N-(phosphonomethyl) glycine) is a broad-spectrum herbicide, acting on the shikimic acid pathway inhibiting 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), thus obstructing the synthesis of tryptophan, phenylalanine, tyrosine and other secondary products. It has also been reported to generate oxidative stress which influences the antioxidant response of target plants. The effect of glyphosate application on total protein, CAT, POD and GST activities was investigated and elevated expression of the oxidative stress enzymes was obtained after glyphosate treatment.Tau-class GSTs are plant-specific, and are chiefly involved in xenobiotics and oxidative stress metabolisms. Many herbicides and safeners have been known to selectively induce tau-class GSTs in different plant species. Here we also report the induction of tau-class GSTs after glyphosate treatment in the seedling roots of two Vigna radiata varieties (PDM11 and PDM54). GSH-agarose affinity chromatography and mass spectrometry revealed that the tau-class GSTs induced in the two varieties were different; the tau-class GSTs present in the untreated controls were also different in the two varieties. The present study highlights the elevated antioxidant response, the induction of tau-class GST and the genotypic variation in the type of tau-GST in control and glyphosate treated varieties of V. radiata.     

Resistance selection and mechanisms of oriental tobacco budworm (Helicoverpa assulta Guenee) to indoxacarb

The oriental tobacco budworm, Helicoverpa assulta, is one of the most destructive pests for numerous commercial crops, and these organisms are responsible for enormous economic losses in Chinese agriculture. Insect larvae often feed within host plant fruits, providing protection from many currently used insecticides and making field control of H. assulta very difficult. Owing to its novel mode of action, high insecticidal activity, and low mammalian toxicity, the nonsystemic insecticide indoxacarb has been considered a promising alternative for the control of lepidopterous pests of agricultural significance. Indoxacarb evidences an elevated insecticidal activity against H. assulta. After 13 generations of selection with indoxacarb and bifenthrin insecticides under laboratory conditions, the LC₅₀ of these compounds for H. assulta increased by 4.19-fold and 10.67-fold, respectively. The synergists diethyl maleate (DEM) and triphenyl phosphate (TPP) increased indoxacarb toxicity by 2.76-fold and 4.10-fold in resistant strains and, comparatively, 1.58-fold and 1.75-fold in susceptible strains, suggesting that carboxylesterase (CarE) and glutathione-S-transferases (GSTs) may be involved in the development of indoxacarb resistance in H. assulta. Activity and kinetic parameters observed in detoxification enzymes further demonstrated that the enhanced activity of CarE and GSTs may be critical in development of indoxacarb resistance in H. assulta. The data provides a foundation for further study of the indoxacarb resistance mechanism observed in H. assulta and the rational use of indoxacarb as a rotation insecticide with other insecticide classes for the control of H. assulta.     

The role of cytochrome P450 monooxygenase in the different responses to fenoxaprop-P-ethyl in annual bluegrass (Poa annua L.) and short awned foxtail (Alopecurus aequalis Sobol.)

Herbicide resistance or tolerance in weeds mediated by cytochrome P450 monooxygenase is a considerable problem. However, cytochrome P450 mediated resistance or tolerance in weeds was less studied. Thus, in this work, the role of the cytochrome P450 monooxygenase in the different responses of Poa annua and Alopecurus aequalis to fenoxaprop-P-ethyl was studied. We found that the effect of fenoxaprop-P-ethyl could be synergized by piperonyl butoxide (PBO) in P. annua, but not by malathion. After being treated with fenoxaprop-P-ethyl (containing mefenpyr-diethyl), the contents of cytochrome P450 and cytochrome b₅ in P. annua increased significantly compared to plants treated with mefenpyr-diethyl only or untreated plants. However, the increase was less in A. aequalis, which was susceptible to fenoxaprop-P-ethyl. The activities of ρ-nitroanisole O-demethylase (PNOD), ethoxyresorufin O-deethylase (EROD), ethoxycoumarin oxidase (ECOD) and NADPH-dependent cytochrome P450 reductase mediated by cytochrome P450 monooxygenase increased in P. annua after treatment with fenoxaprop-P-ethyl, especially the activities of ECOD and cytochrome P450 reductase. Besides this, cytochrome P450 monooxygenase activity toward fenoxaprop-P-ethyl in P. annua increased significantly compared to untreated or treated with mefenpyr-diethyl plants and treated or untreated A. aequalis. Cytochrome P450 monooxygenase may play an important role in the different responses to fenoxaprop-P-ethyl in P. annua and A. aequalis.     

NbRbohB基因在本氏烟与疫霉菌互作中的功能分析

活性氧(active oxygen species, AOS)在植物抗病中发挥着重要作用,主要由NADPH氧化酶(nicotinamide adenine dinucleotide phosphate oxidase)系统产生.为明确NADPH氧化酶NbRbohB基因在本氏烟与疫霉菌亲和与非亲和性互作中的功能,采用荧光定量PCR技术以及病毒诱导的基因沉默方法探究了NbRbohB基因在本氏烟中对2种疫霉菌抗性中的作用,并利用NADPH氧化酶抑制剂对辣椒疫霉的抗性进行了检测.结果发现:2种疫霉菌均能诱导本氏烟发生氧迸发,且NbRbohB基因可能参与了疫霉菌诱导本氏烟发生的氧迸发过程.该基因沉默后降低了本氏烟对亲和互作辣椒疫霉菌的抗性,但对非亲和互作疫霉菌的抗性没有肉眼可见的影响;NADPH氧化酶抑制剂处理本氏烟后也能降低其对辣椒疫霉的抗性.表明该基因通过介导AOS产生,参与植物对亲和性与非亲和性互作疫霉的抗病反应,在亲和互作中尤为重要.     

Methylparathion- and carbofuran-induced mitochondrial dysfunction and oxidative stress in Helicoverpa armigera (Noctuidae: Lepidoptera)

The cotton bollworm, Helicoverpa armigera is a polyphagous pest of several crops in Asia, Africa, and the Mediterranean Europe. Organophosphate and carbamate insecticides are used on a large-scale to control Helicoverpa. Therefore, we studied the effect of methylparathion and carbofuran, an organophosphate and carbamate insecticide, respectively, on oxidative phosphorylation and oxidative stress in H. armigera larvae to gain an understanding of the different target sites of these insecticides. It was observed that state III and state IV respiration, respiratory control index (RCI), and P/O ratios were inhibited in a dose-dependent manner by methylparathion and carbofuran under in vitro and in vivo conditions. Methylparathion and carbofuran inhibited complex II by ∼45% and 30%, respectively. Lipid peroxidation, H₂O₂ content, and lactate dehydrogenase (LDH) activity increased and glutathione reductase (GR) activity decreased in a time- and dose-dependent manner in insecticide-fed larvae. However, catalase activity was not affected in insecticide-fed larvae. Larval growth decreased by ∼64% and 67% in larvae fed on diets with 100 μM of methylparathion and carbofuran. The results suggested that both the insecticides impede the mitochondrial respiratory functions and induced lipid peroxidation, H₂O₂, and LDH leak, leading to oxidative stress in cells, which contribute to deleterious effects of these insecticides on the growth of H. armigera larvae, along with their neurotoxic effects.     

二化螟盘绒茧蜂寄生对寄主二化螟幼虫免疫反应的影响

为了探明二化螟盘绒茧蜂Cotesia chilonis (Matsumura)寄生对寄主二化螟Chilo suppressalis (Walker)幼虫血细胞和体液免疫反应的影响,观察并测定了二化螟盘绒茧蜂寄生引起二化螟幼虫血细胞数量、延展、存活、吞噬和包囊作用以及血淋巴酚氧化酶活性等的变化。结果显示,二化螟幼虫血细胞总数在寄生后1天即显著高于对照。其中,颗粒血细胞和浆血细胞在寄生后的数量变化均与血细胞总数变化相似,颗粒血细胞在寄生后3天、浆血细胞在寄生后0.5天起即分别与其对照差异显著,但两种血细胞在血细胞总数中各自所占的比例与对照多无显著差异。二化螟幼虫血细胞延展能力在寄生后0.5天受到显著抑制,此后与对照无显著差异;同时寄生可增加寄主血细胞的死亡率。寄主幼虫血细胞的吞噬作用在寄生后2天起显著降低;包囊作用则在寄生后1天起显著降低。二化螟幼虫被二化螟盘绒茧蜂寄生后,血淋巴酚氧化酶活性显著升高,但随后呈逐渐下降趋势。研究结果说明,二化螟盘绒茧蜂寄生使寄主二化螟幼虫的免疫反应呈现一定的规律变化。     

Prevention of progeny formation in Drosophila melanogaster by 1-arylimidazole-2(3H)-thiones

Effects of 1-arylimidazole-2(3H)-thiones (AITs) and 1-(substituted benzyl)imidazole-2(3H)-thiones (BITs) were tested on progeny formation in Drosophila melanogaster. Some AITs showed inhibitory activities at laying eggs and delayed eclosion by 1 day. The inhibitory activity was nullified by adding octopamine (OA) or noradrenaline (NA) to the medium for progeny formation in D. melanogaster. The effect of AIT on the contents of OA and NA was analyzed in adults of D. melanogaster by high-performance liquid chromatography with electrochemical detection. Flies fed with AIT decreased OA and NA levels and increased TA content. Taken together, the inhibitory activity of AIT could be due to inhibition of tyramine β-hydroxylase and dopamine β-hydroxylase.     

Resistance selection and biochemical mechanism of resistance to two Acaricides in Tetranychus cinnabarinus (Boiduval)

A Tetranychus cinnabarinus strain was collected from Chongqing, China. After 42 generations of selection with abamectin and 20 generations of selection with fenpropathrin in the laboratory, this T. cinnabarinus strain developed 8.7- and 28.7-fold resistance, respectively. Resistance to abamectin in AbR (abamectin resistant strain) and to fenpropathrin in FeR (fenpropathrin resistant strain) was partially suppressed by piperonyl butoxide (PBO), diethyl maleate (DEM) and triphenyl phosphate (TPP), inhibitors of mixed function oxidase (MFO), glutathione S-transferases (GST), and hydrolases, respectively, suggesting that these three enzyme families are important in conferring abamectin and fenpropathrin resistance in T. cinnabarinus. The major resistant mechanism to abamectin was the increasing activities of carboxylesterases (CarE), glutathione-S-transferase (GST) and mixed function oxidase (MFO), and the activity in resistant strain developed 2.7-, 3.4- and 1.4-fold contrasted to that in susceptible strain, respectively. The activity of glutathione-S-transferase (GST) in the FeR strain developed 2.8-fold when compared with the susceptible strain, which meant the resistance to fenpropathrin was related with the activity increase of glutathione-S-transferase (GST) in T. cinnabarinus. The result of the kinetic mensuration of carboxylesterases (CarE) showed that the structure of CarE in the AbR has been changed.     

Effect of dietary benzoxadiazole on larval development, cuticle enzyme and antioxidant defense system in housefly (Musca domestica L.)

The toxicity and influence on chronic development regulation of dietary benzoxadiazole as well as the subsequent action on cuticle enzyme and antioxidant defense system in feed-thru housefly larvae are investigated. Dietary benzoxadiazole shows limited larvicidal activity and weak interference on larval pupation, but strong blockage against the succedent eclosion process. It does not change the content ratio of protein/chitin in the larval cuticle, but strongly regulates the constituents of cuticle proteins. Moreover, chitinase activities in the integument of third-instar larvae, in vivo, are enhanced and gradually decreased whereas phenoloxidase activities are inhibited and the inhibitory rates are gradually increased. Glutathione S-transferase activities are strongly improved whilst peroxidase activities decrease from about 42.25% to 17.36%, catalase activities decrease from about 80.31% to 27.98% and superoxide dismutase activities are almost unchanged during the different treatment procedures. Peroxidase SDS-PAGE analysis shows that band photodensities of 200.0 and 10.3 kDa proteins in feed-thru larvae are significantly weaker than the corresponding control band. Results suggest that dietary benzoxadiazole might exert strong regulation on larvae cuticle metabolism, interfere with cuticle enzymatic browning and protein sclerotization and weaken the self-protection of larvae against endogenetic oxidative damages.     

枣镰翅小卷蛾成虫的寄主趋向和产卵选择

采用固相微萃取(SPME)和GC-MS分析研究木枣和酸枣挥发物成分,并测试枣镰翅小卷蛾触角电位(EAG)反应、寄主趋向和产卵选择,以探明枣镰翅小卷蛾的寄主选择机制。结果显示,在萌芽期,木枣和酸枣嫩叶的挥发成分均为罗勒烯、2-甲基-2-菠烯、α-法呢烯和邻苯二甲酸二丁酯4种,但相对含量稍有不同。枣镰翅小卷蛾成虫对木枣和酸枣2种寄主都有强烈的EAG反应,且同一寄主上雌蛾的EAG反应值极显著地高于雄蛾,其EAG值是雄蛾的3.3倍。枣镰翅小卷蛾对木枣表现强烈的趋向反应,而对酸枣的趋向不明显,且雌虫的趋向反应显著高于雄虫。木枣上的产卵量显著高于酸枣,且木枣枣吊上的单雌产卵量为307.9粒,极显著地高于酸枣枣吊上的产卵量(182.9粒)。研究表明,枣镰翅小卷蛾雌蛾在寄主选择中起主导作用,木枣是其嗜好寄主。     

Generation of reactive oxygen species by a novel anthraquinone derivative in the cyanobacterium Planktothrix perornata (Skuja)

A water-soluble anthraquinone derivative (2-[methylamino-N-(1′-methylethyl)]-9,10-anthraquinone monophosphate), previously found to be selectively toxic towards Planktothrix perornata at submicromolar concentrations, was studied to determine its toxic mode of action towards this cyanobacterium. Chlorophyll fluorescence was monitored as an indicator of photosynthetic efficiency, and measurement of reactive oxygen species (ROS) was performed using the ROS-sensitive probe 2′,7′-dichlorodihydrofluorescein diacetate. The effects of the herbicide paraquat (a ROS generator) as well as ascorbate and α-tocopherol (ROS scavengers) on ROS formation by P. perornata were studied. Also, the effects of different concentrations of ascorbate, α-tocopherol, and the herbicide diuron on reducing the toxicity of the water-soluble anthraquinone derivative towards P. perornata were determined. Our results indicate that the water-soluble anthraquinone derivative does not inhibit photosynthetic electron transport directly, but does generate ROS at levels that may cause toxicity towards P. perornata.     

Effect of short term exposure of fenvalerate on biochemical and haematological responses in Labeo rohita (Hamilton) fingerlings

Experiment was carried out to determine the median lethal concentration (LC₅₀) of fenvalerate to Labeo rohita fingerlings. After determining the LC₅₀ value of fenvalerate, a sub-lethal concentration (1/3rd of LC₅₀) of fenvalerate was exposed for 15 days. Significant alterations in SOD (P < 0.05) activity of liver and gill was observed due to fenvalerate. Catalase activity in gills of fishes was also affected significantly (P < 0.05). WBC, NBT and Hct values were reduced significantly in fenvalerate exposed fishes as compared to control group, whereas blood glucose level showed higher values in fenvalerate exposed group. Serum total protein and albumin were also reduced significantly as a result of fenvalerate exposure. Significant increase in the serum GOT, serum GPT, creatinine, triglyceride and serum ACP was noticed after 15 days of fenvalerate exposure. Results indicated that short term exposure of fenvalerate can induce biochemical and haematological alterations causing stress to L. rohita fingerlings.     

Methoxyfenozide and pyriproxifen alter the cellular immune reactions of Eurygaster integriceps Puton (Hemiptera: Scutelleridae) against Beauveria bassiana

Effects of the two insect growth regulators (IGRs) methoxyfenozide, 20-hydroxyecdysone (20E) agonist, and pyriproxifen, Juvenile hormone (JH) agonist, were examined on the cellular immune responses of the Sunn pest, Eurygaster integriceps versus the entomopathogenic fungus Beauveria bassiana. The simultaneous treatment with the IGRs and the fungal spores altered haemocyte count (total and differentiate), nodulation response and phenoloxidase (PO) activity in a dose- and time-dependent manner. It was observed that different concentrations of methoxyfenozide increased total and differentiate haemocyte numbers as well as B. bassiana-induced nodulation response. In contrast with the JH agonist, pyriproxifen significantly decreased total and differentiate haemocyte numbers and inhibited nodule formation in E. integriceps adults. The 20E agonist displayed major effects when injected at the doses 2.79 and 5.59 μg/mg adult. In contrast, injecting adults by pyriproxifen significantly impaired their ability to raise an efficacious response against the fungal spores. The ability of the two IGR analogues to interfere with activity of the PO system in haemolymph of E. integriceps adults was also investigated 6 h after injection by fungal spores. Methoxyfenozide had an excitatory effect on PO activity when the 5.59 μg/mg concentration was used against adults. Conversely, pyriproxifen had an inhibitory effect on PO activity when used at 1.49 μg/mg adult concentration. These findings demonstrate that pyriproxifen may interfere with cell-mediated immunity of E. integriceps. So, pyriproxifen could be a good candidate for the integrated control of the Sunn pest.     

葡萄应答霜霉病过程中多磷酸肌醇激酶基因与过氧化氢的作用机制

以对霜霉病不同抗性的葡萄品种左优红和霞多丽为材料,利用分子生物学和植物生理学试验手段,结合药理学试验,探讨葡萄在应答霜霉病过程中葡萄多磷酸肌醇激酶基因（VvIPK2）和H2O2的作用机制。接种霜霉病菌后15 h葡萄叶片VvIPK2表达量是正常水平的12倍,接种后3 hH2O2含量达最大值,同时苯丙氨酸解氨酶和几丁质酶活性升高;多磷酸肌醇激酶（IPK2）抑制剂、外源H2O2及H2O2清除剂均能改变霜霉病菌所引起的抗性葡萄品种左优红叶片PAL和几丁质酶活性的变化,同时可以影响不同抗性品种叶片的感病情况;IPK2抑制剂对葡萄霜霉病菌引起的H2O2水平变化没有影响;清除H2O2可减弱葡萄霜霉病菌对VvIPK2表达量的诱导效应。研究表明H2O2位于IPK2的上游,通过调控PAL和几丁质酶活性参与葡萄应答霜霉病过程。     

The effects of Artemisia annua L. and Achillea millefolium L. crude leaf extracts on the toxicity, development, feeding efficiency and chemical activities of small cabbage Pieris rapae L. (Lepidoptera: Pieridae)

The biological effects of two important medicinal plants, Artemisia annua L. and Achillea millefolium (L.) (viz, mortality, growth, and feeding indices as well as enzyme and non-enzymatic activities) were studied on small white Pieris rapae L a deleterious pest of cruciferous plants under controlled conditions (16:8 h L:D at 25 ± 1 °C and 65 ± 5% RH). The LC₅₀ and LC₂₅ values were 9.387% and 3.645% for A. annua L. and 4.19% and 1.69% for A. millefolium (L.), respectively. At the lowest concentration (0.625%), the deterrency was 29.826% and 44.185% for A. annua L. and A. millefolium (L.), respectively. Feeding indices were variously affected with changes in a number of parameters and an increase in larval and pupal duration. The activity level of alkaline phosphatase increased sharply while alanin and aspartate aminotransferases showed a sharp decrease. For non-enzymatic compounds, the amount of glucose and uric acid increased, but total protein and cholesterol decreased. These results indicate that these two medicinal plants might possess potential secondary metabolites that may be useful for controlling potential insect pests.     

低温胁迫对异色瓢虫成虫存活及体内几种酶活力的影响

为探讨低温胁迫对异色瓢虫存活的影响以及冷伤害机制,采用温度和时间双因子处理测定了低温暴露中异色瓢虫成虫的存活率及其体内4种酶活性变化。结果表明:过冷却点以上的低温(-5、-7℃)就能导致异色瓢虫成虫大量死亡,随着温度的降低和暴露时间的延长,成虫存活率显著降低;暴露在-1、-3、-5和-7℃下的半致死时间LT50分别为8.30、6.68、3.54和1.24 d,且随着温度的降低,LT50显著降低。异色瓢虫成虫体内过氧化氢酶和过氧化物酶活性随着温度的降低及暴露时间的延长而明显升高,在-10℃和-5℃下暴露10 d时活性达到最高,分别为679.73 U/g和396.06 mg/m L;而乳酸脱氢酶和Na+、K+-ATP酶活性随着低温胁迫时间的延长而降低。表明低温下异色瓢虫成虫体内细胞保护酶系统的防御能力趋强而有利于增强低温抵抗力,但会影响其体内代谢产物及离子运输,长时间的低温胁迫甚至会引起代谢紊乱。