Recovery from inhibition of photosynthesis by metamitron in various plant species

Inhibition of photosynthesis by metamitron in the rooting medium and its subsequent recovery after transfer of the roots to herbicide-free nutrient solution was measured in eight plant species. Fast and complete recovery within a few hours after treatment showed that metamitron, once absorbed, was rapidly and completely inactivated in the leaves of sugar beet (Beta vulgaris L.). Inactivation in perennial ryegrass (Lolium perenne L.) was slower and incomplete. It was low in Echinochloa crusgalli (L.) P.B., Amaranthus retroflexus L., Alopecurus myosuroides Huds. and bean (Phaseolus vulgaris L.), and undetectable in maize (Zea mays L.) and Portulaca oleracea L. From the transpiration rate and the concentration of metamitron in the nutrient solution that just did not cause inhibition of photosynthesis in sugar beet, uptake and inactivation rates per unit leaf area were calculated to be at least 18·5 ng/cm²/h. The same external concentration markedly depressed photosynthesis in the other more susceptible species. After leaf sprays sugar beet plants gradually resumed the normal rate of photosynthesis, but bean plants did not recover.     

Life tables of Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) (Lepidoptera: Noctuidae) on different cultivated plants

Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) is a cosmopolitan species that feeds on numerous cultivated plants and herbaceaus plants. Agrotis ipsilon causes significant economic losses in various agricultural products, especially in indisturial plants and vegetables in Turkey and worldwide. In this study, the effects on the biology and reproductive potential of lettuce (Lactuca sativa L., Asteraceae), maize (Zea mays L., Poaceae), sugarbeet (Beta vulgaris var. saccharifera Alef.,Amaranthaceae) and potato (Solanum tuberosum L., Solanaceae) which are essential host plants of A. ipsilon were investigated under climatized conditions of 28?±?1 °C, 60%?±?10 r.h., and 16 h daily artificial light. The data obtained were analyzed by using an age-stage two-sex life table. Agrotis ipsilon had five larval stages fed on lettuce, whereas seven larval stages were fed on other host plants. Agrotis ipsilon showed the best development and reproduction on lettuce, followed by sugar beet. When A. ipsilon is reared on lettuce the intrinsic rate of increase (r?=?0.1237 d^?1), finite rate of increase (λ?=?1.1317 d^?1) and net reproductive rate (R₀?=?403.06 offspring/individual) were found higher and the mean generation times (T?=?48.51 d) is shorter than those in other host plants. According to these results, A. ipsilon can cause the most damage to lettuce among studied plants.

     

甘草根腐病病原菌鉴定

 甘草(Glycyrrhiza uralensis Fish.)别名甜草、蜜草、甜根子, 为豆科多年生草本植物, 以根与根茎入药, 具有补脾益气、清热解毒、祛痰止咳、缓急止痛、调和诸药之功效, 是我国临床常用的中药材, 也可用作食品添加剂。甘草主要分布在我国的内蒙古、甘肃和宁夏, 在青海、陕西、新疆、黑龙江、辽宁、吉林、河北、山西等地局部地区也有分布。宁夏盐池县是我国乌拉尔甘草的重要产区, 面积大、贮量多、品质好, 1995年被誉为“中国甘草之乡” ^[1]。近年来, 野生甘草遭到了大规模采挖, 甘草蕴藏量急剧减少, 目前主要通过人工种植来满足市场需求。随着甘草种植面积的不断扩大, 甘草病虫害日趋严重, 根腐病危害尤为突出, 直接影响甘草的产量和品质, 造成巨大经济损失。     

Retention,absorption, translocation and distribution of sethoxydim in monocotyledonous and dicotyledonous plants*

Quackgrass [Elymus repens (L.) Gould =Agropyron repens (L.) Beauv.] and barnyardgrass [Echinochloa crus-galli (L.) Beauv.] were more than one hundred times more susceptible to sethoxydim than alfalfa (Medicago sativa L. 'Saranac') or navybean (Phaseolus vulgaris L. 'Seafarer'). Uptake of sethoxydim From soil following post-emergence applications caused negligible reduction in E. crus-galli fresh weight. More than 80% of foliar-applied ¹⁴C-sethoxydim was absorbed within 6 h in all species. Translocation occurred in all species with accumulation of ¹⁴C in rapidly growing plant tissues. Translocation to the roots was less than 8% of total in all species. Most of the extracted ¹⁴C initially partitioned into an ethyl acetate-soluble fraction. The proportion of ¹⁴C in the ethyl acetate-soluble fraction decreased with time with a concomitant increase of that in the insoluble fraction. Differences in the quantity of ¹⁴C in the ethyl acetate-soluble fraction did not account for the observed selectivity.     

Host Range ofVerticillium dahliae in cultivated species in Crete

To determine the host range ofVerticillium dahliae among the cultivated species in Crete, Greece, studies were carried out during 1992–2000. Based on disease symptoms observed on 28 vegetable and forage species grown in a field naturally infected byV. dahliae, and an extensive survey of the most common cultivated species grown under natural conditions, seven hosts belonging to four botanical families not previously reported as susceptible to Verticilliun wilt, and 12 hosts belonging to seven families new for Greece, were recorded. The worldwide new hosts are: anise (Anethum graveolens), chard (Beta vulgaris ssp.cicla), chickpea (Cicer arietinum), wild sweet pea (Lathyrus ochrus), lentil (Lens culinaris), marigold (Tagetes erecta) and vetch (Vicia sativa). These species could be infected by their hosts-of-originV. dahliae isolates during pathogenicity tests. http://www.phytoparasitica.org posting Jan. 13, 2002.     

黄土高原农牧交错带退耕坡地苜蓿-铁杆蒿群落养分分布特征

植物群落养分的空间分布反映了生态系统物质循环特征,可以为揭示生态系统资源的有效性及生态系统中植物群落的演替过程提供依据。本研究以黄土高原农牧交错带退耕坡地苜蓿-铁杆蒿群落为对象,分析其生物量和养分含量的空间分布特征。结果表明:退耕地苜蓿-铁杆蒿群落坡上部以苜蓿为主导物种,坡下部以铁杆蒿为主导物种,坡中部由二者共同主导。同一植物的生物量和N含量具有相似的空间结构,并且与植物种类有关;苜蓿和铁杆蒿P含量均以球状模型最佳,K含量的空间分布均以高斯模型最佳。苜蓿-铁杆蒿群落生物量和养分含量具有较强的空间依赖性,其空间变异主要由结构性因素决定。苜蓿和铁杆蒿生物量和养分含量的自相关性随距离变化表现出相似的趋势,但随生物量和养分种类的不同而异,且铁杆蒿生物量和养分含量的自相关性大于苜蓿。随着人工草地向天然草地的演替,群落生物量和养分含量的空间自相关性和空间依赖性逐渐增强。     

Host Range of Oidium lycopersici Occurring in the Netherlands

Nine accessions of three cucurbit species, ten of eight legume species, three of lettuce (Lactuca sativa) and 34 of 14 Solanaceae species were inoculated with a Dutch isolate of the tomato powdery mildew fungus (Oidium lycopersici) to determine its host range. Macroscopically, no fungal growth was visible on sweet pepper (Capsicum annuum), lettuce, petunia (Petunia spp.) and most legume species (Lupinus albus, L. luteus, L. mutabilis, Phaseolus vulgaris, Vicia faba, Vigna radiata, V. unguiculata). Trace infection was occasionally observed on melon (Cucumis melo), cucumber (Cucumis sativus), courgette (Cucurbita pepo), pea (Pisum sativum) and Solanum dulcamara. Eggplant (Solanum melongena), the cultivated potato (Solanum tuberosum) and three wild potato species (Solanum albicans, S. acaule and S. mochiquense) were more heavily infected in comparison with melon, cucumber, courgette, pea and S. dulcamara, but the fungus could not be maintained on these hosts. All seven tobacco (Nicotiana tabacum) accessions were as susceptible to O. lycopersici as tomato (Lycopersicon esculentum cv Moneymaker), suggesting that tobacco is an alternative host. This host range of the tomato powdery mildew differs from that reported in some other countries, which also varied among each other, suggesting that the causal agent of tomato powdery mildew in the Netherlands differ from that in those countries. Histological observations on 36 accessions showed that the defense to O. lycopersici was associated with a posthaustorial hypersensitive response.     

Quantitative trait loci associated with resistance to a potato isolate of Verticillium albo‐atrum in Medicago truncatula

Verticillium albo‐atrum is responsible for considerable yield losses in many economically important crops, among them alfalfa (Medicago sativa). Using Medicago truncatula as a model for studying resistance and susceptibility to V. albo‐atrum, previous work has identified genetic variability and major resistance quantitative trait loci (QTLs) to Verticillium. In order to study the genetic control of resistance to a non‐legume isolate of this pathogen, a population of recombinant inbred lines (RILs) from a cross between resistant line F83005.5 and susceptible line A17 was inoculated with a potato isolate of V. albo‐atrum, LPP0323. High genetic variability and transgressive segregation for resistance to LPP0323 were observed among RILs. Heritabilites were found to be 0·63 for area under the disease progress curve (AUDPC) and 0·93 for maximum symptom score (MSS). A set of four QTLs associated with resistance towards LPP0323 was detected for the parameters MSS and AUDPC. The phenotypic variance explained by each QTL (R²) was moderate, ranging from 4 to 21%. Additive gene effects showed that favourable alleles for resistance all came from the resistant parent. The four QTLs are distinct from those described for an alfalfa V. albo‐atrum isolate, confirming the existence of several resistance mechanisms in this species. None of the QTLs co‐localized with regions involved in resistance against other pathogens in M. truncatula.     

Nematicidal potential of materials from <Emphasis Type="Italic">Medicago</Emphasis> spp.

The nematicidal effect of soil amendments with dry top and root material from Medicago sativa and/or Medicago arborea was evaluated on the root-knot nematode Meloidogyne incognita and on the cyst nematode Globodera rostochiensis in potting mixes. All amendments suppressed root and soil population densities of both nematode species compared to non-treated and chemical controls. The suppressiveness of M. sativa differed between top and root material and among the amendment rates. In field conditions soil amendments with 20 or 40 t ha⁻¹ of a pelleted M. sativa meal increased tomato crop yield and reduced soil population densities and root galling by M. incognita. It is suggested that saponins were at least partly responsible for the nematicidal activity.     

Über die Beeinflussung der Keimfähigkeit der Samen mancher Grundlandpflanzen beim Durchgang durch den Verdauungstrakt des Schafes und nach Mistgärung

Bei den mit 10-monatigen Schafböcken durchgeführten Versuchen wurden folgende Ergebnisse erhalten: Die Ausscheidungsrate (Versuehsdauer 96 Stunden nach Verfutterung) der Samen von lOverfutterten Weidepflanzenarten betrug bei Medicago sativa 55,5%, Phteum pratense 53,4%, Coronitta varia 42,8%, Lotus cornicutatus 34,8%, Agrostis alba 32,9%, Trifotium repens 24,5%, Stipaviriduta 16,6%, Vicia sativa 9,3%, Hordeum nodosum 1,4%, Onobrychis sativa 0,8%. Ausscheidungszeiten: Ohne bestimmte zeitliche Regelmäßigkeiten wurden die Samen von Hordeum nodosum im Verlauf der 96-stündigen Versuehsdauer ausgeschieden. Bei Medicago sativa wurde ein Ausscheidungsmaximum bei 62 Stunden, bei Phteum pratense bei 86 Stunden festgestellt. Bei den anderen 7 Samenarten lag das Ausscheidungsmaximum zwischen 38–48 Stunden. Wahrend bei 8 Samenarten eine Verminderung der Keimfähigkeit nach Passieren des Verdauungstrakts im Vergleich zu frischen Samen festgestellt wurde, konnte man eine Erhöhung des Keimwertes bei Agrostis atba und Hordeum nodosum feststellen. Keimfahig waren die Samen von Vicia sativa bis zu einer Ausscheidungszeit von 38 Stunden, Onobrychis sativa bis 48 Stunden. Samen von Hordeum nodosum waren keimfahig bis zu einer Ausscheidungszeit von 62–96 Stunden, Trifotium repens 24–86 Stunden. Bei den restlichen 6 Arten waren die Samen auch nach 96-stündiger Verweildauer im Verdauungstrakt zumindest noch teilweise keimfähig. Nach 3-monatiger Mistgärung waren die Samen von Vicia sativa, Hordeum nodosum und Onobrychis sativa vollig vernichtet. Bei den restlichen 7 Samenarten betrug die Keimpotenz bei Coronitta varia 6,8%, Lotus cornicutatus 6,1%, Trifotium repens 5,1%, Phteum pratense 4,9%, Medicago sativa 4,6%, Agrostis alba 3,2% und Stipa viridula 1,1%.     

Residues of Mecoprop in Post-emergence-Treated Wheat and Oat

The dissipation of mecoprop in wheat (Triticum aestivum L.) and oat (Avena sativa L.) was monitored over a growing season following post-emergence application of the dimethylamine salt of mecoprop to each crop at 1·1 kg ha^?1. Residues of mecoprop, as its methyl ester, were determined gas chromatographically using electrolytic conductivity detection. Initial residues in wheat (119 (±20) mg kg^?1) and oat (95·3 (± 10·0) mg kg^?1) on the day of application (four-leaf stage of wheat and four- to five-leaf stage of oat) decreased to 0·1 to 0·2 mg kg^?1, respectively, within six weeks. Residues were non-detectable in the mature seed of both crops. Recoveries of mecoprop were in the order of 90% from the green tissue and seed of both crops fortified at 0·05 mg kg^?1.     

Photosynthetic and accessory pigments in Cuscuta campestris Yuncker and some host species

Photosynthetic and accessory pigments (chlorophyll a and b, a and ß carotenes and xanthophylls) were evaluated in Cuscuta campestris Yuncker during the course of its biological cycle, taking into account both autotrophic and heterotrophic phases, and different parts of the parasite. Chloroplast activity in C. campestris was measured and comparisons were made with the chloroplast activity in Beta vulgaris L. and Convolvulus arvensis L. The effects of parasitization of C. campestris on the main and accessory photosynthetic pigments of B. vulgaris were also evaluated. Finally, a hypothesis was formulated to explain the different distribution of pigments in different parts and at different stages of the growth cycle in C. campestris and its chloroplast activity. Pigments photosynthétiques principaux et accessoires chez Cuscuta campestris Yuncker et des espèces hôtes Les pigments photosynthétiques principaux et accessoires (chlorophylles a et b, α et β carotènes, xanthophylles) ont été déterminés chez Cuscuta campestris Yuncker durant son cycle biologique. Les phases auttorophes et hétérotrophes ont été prises en compte et les mesures ont porté sur différentes parties des plantes. L'activité chloroplastique a été déterminée chez C. campestris et a été comparéà celles de Beta vulgaris L. et de Convolvulus arvensis L. Les conséquences du parasitisme de C. campestris sur les pigments principaux et accessoires de B. vulgaris ont aussi étéétudiées. Enfin, une hypothèse a été avancée pour expliquer les différences de distribution des pigments dans les différentes parties de C. campestrisà divers stades de son cycle biologique, ainsi que son activité chloroplastique. Photosynthese- und akzessorische Pigmentre in Cuscuta campestris Yuncker und einigen Wirstspflanzenarten Bei Cuscuta campestris Yuncker wurden im Verlaufe ihres Lebenszyklus die Photosynthese- und akzessorischen Pigmenten (Chlorophyll a und b, a- und ß-Karotin, Xanthophylle) sowohl in autotrophen als auch heterotrophen Phasen und in verschiedenen Pflanzenteilen untersucht. Die Chloroplastenaktivität wurde gemessen und mit der von Beta vulgaris L. und Convolvulus arvensis L. vergleichen. Die Wirkung der Parasitierung von Cuscuta campestris auf die Photosynthese-Pigmente von Beta vulgaris wurd erfaßt. Eine Hypothese über die Chloroplastenaktivität und zur verschiedenen Verteilung der Pigmente in den verschiedenen Pflanzenteilen und in verschiedenen Entwicklungsstadien von Cuscuta campestris wurde formuliert.     

Review of anthraquinone applications for pest management and agricultural crop protection

We have reviewed published anthraquinone applications for international pest management and agricultural crop protection from 1943 to 2016. Anthraquinone (AQ) is commonly found in dyes, pigments and many plants and organisms. Avian repellent research with AQ began in the 1940s. In the context of pest management, AQ is currently used as a chemical repellent, perch deterrent, insecticide and feeding deterrent in many wild birds, and in some mammals, insects and fishes. Criteria for evaluation of effective chemical repellents include efficacy, potential for wildlife hazards, phytotoxicity and environmental persistence. As a biopesticide, AQ often meets these criteria of efficacy for the non‐lethal management of agricultural depredation caused by wildlife. We summarize published applications of AQ for the protection of newly planted and maturing crops from pest birds. Conventional applications of AQ‐based repellents include preplant seed treatments [e.g. corn (Zea mays L.), rice (Oryza sativa L.), sunflower (Helianthus annuus L.), wheat (Triticum spp.), millet (Panicum spp.), sorghum (Sorghum bicolor L.), pelletized feed and forest tree species] and foliar applications for rice, sunflower, lettuce (Lactuca sativa L.), turf, sugar beets (Beta vulgaris L.), soybean (Glycine max L.), sweet corn and nursery, fruit and nut crops. In addition to agricultural repellent applications, AQ has also been used to treat toxicants for the protection of non‐target birds. Few studies have demonstrated AQ repellency in mammals, including wild boar (Sus scrofa, L.), thirteen‐lined ground squirrels (Ictidomys tridecemlineatus, Mitchill), black‐tailed prairie dogs (Cyomys ludovicainus, Ord.), common voles (Microtus arvalis, Pallas), house mice (Mus musculus, L.), Tristram's jirds (Meriones tristrami, Thomas) and black rats (Rattus rattus L.). Natural sources of AQ and its derivatives have also been identified as insecticides and insect repellents. As a natural or synthetic biopesticide, AQ is a promising candidate for many contexts of non‐lethal and insecticidal pest management. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.     

An investigation of herbicide interaction with the H+-ATPase activity of plant plasma membranes

This study has investigated the activity of several herbicide classes at the plant plasma membrane. Two-phase partitioning was used to prepare highly purified plasma membrane vesicles from the monocotyledon weed black-grass (Alopecurus myosuroides Huds.) and the dicotyledon crop sugar beet (Beta vulgaris L. cv. Celt). The purity of the plasma membrane H⁺-ATPase activity was characterised with respect to inhibitors, pH and substrate specificity. In both species, contamination of the plasma membrane by tonoplast fragments was largely eliminated and chlorophyll was absent. In addition, the plasma membrane H⁺-ATPase from black-grass and sugar beet exhibited high vanadate sensitivity and a sharp pH profile around 6·5. Subsequently, H⁺-ATPase activity was assayed in the presence (100 μM ) and absence of four graminicide classes and auxin-type herbicides. Graminicides, including the aryloxyphenoxypropionate diclofop-methyl and the thiocarbamate triallate, inhibited H⁺-ATPase activity by 50–80% in both species. However, other graminicides, including the cyclohexanediones and the chloroacetamide alachlor, had no affect. Similarly, auxin-type herbicides such as 2,4-D and MCPA did not inhibit H⁺-ATPase activity. Results are discussed in relation to the proposed mode of action of these herbicides. © 1998 SCI     

A new bacterial leaf blight disease of oat (Avena sativa) caused by Pantoea agglomerans in China

A new leaf blight disease of oat (Avena sativa) was observed in many oat fields in Huan county, Gansu Province of China, during 2018–2019. Typical symptoms appeared as yellow necrotic and water-soaked lesions. The lesions developed from tip to base of leaves and eventually resulted in leaf withering. Disease incidence on plants (leaves) was approximately 36%–100%. A gram-negative bacterium was isolated from the necrotic lesions of all samples. Coupled with multigene sequence (16S rRNA and gyrB gene) analyses, Biolog Gen III MicroStation, morphological, physiological, and biochemical characterization identified the pathogen as Pantoea agglomerans. Pathogenicity tests by wounding and injection inoculations in the greenhouse established that P. agglomerans could induce typical symptoms as observed in the field. The infection rate in leaves was 44%–71% after 14 days. In addition, host range tests showed that P. agglomerans could infect other plant hosts, including Sorghum sudanense, Medicago sativa, Fagopyrum esculentum, Setaria italica, and Zea mays. This is the first report of P. agglomerans causing bacterial leaf blight disease (LBD) on oat in China. The current study can provide a foundation for the prevention of this disease in the future.     

Selectivity and mode of action of carfentrazone-ethyl,a novel phenyl triazolinone herbicide

Post-emergence application of carfentrazone-ethyl at rates as low as 2·2 g ha^-1 caused greater leaf injury and growth reduction in ivyleaf morningglory (Ipomoea hederacea) and velvetleaf (Abutilon theophrasti) than in soybean (Glycine max). The herbicide was more rapidly metabolized in the crop than in the weed species, with 26·7, 54·3 and 60·6% of the parent compound remaining in soybean, ivyleaf morningglory and velvetleaf, respectively, 24 h after exposure. The free acid metabolite, carfentrazone, was present in all species and accounted for 21·2–27·4% of the total radioactivity. Unknown metabolites (R_f 0 and 0·22) were four to five times more abundant in soybean than in the weed species. Carfentrazone-ethyl induced more leakage from leaf discs from the weeds than those from soybean and the degree of injury correlated with the amount of protoporphyrin IX (Proto IX) present in the treated tissues. Both carfentrazone-ethyl and carfentrazone were potent inhibitors of protoporphyrinogen oxidase (Protox). Therefore, the selectivity of this herbicide may, at least in part, be attributed to the lower accumulation of Proto IX in soybean than in the weeds, probably because of the ability of soybean to metabolize more carfentrazone into unknown metabolites than the weeds. © 1997 SCI.     

Seasonal activity of EPTC for Cyperus rotundus L. control in a tropical climate*

Four experiments were conducted at six week intervals to determine the seasonal activity and persistence of soil-incorporated EPTC (5-ethyl N,N-dipropyl(thiocarbamate)) for Cyperus rotundus L. control and tolerance of okra (Hibiscus esculentus L.), cucumber (Cucumis sativus L.), lettuce (Lactuca sativa L.), red beet (Beta vulgaris L.) and carrot (Daucus carota L.) during the dry and wet seasons in Viçosa, Brazil. Satisfactory control of C. rotundus was obtained at 2 kg/ha EPTC during the dry season and 4 kg/ha or more during the wet season. Only red beet and carrot tolerated these doses of EPTC when the crops were planted five days after application. However, selective control of C. rotundus was obtained when the planting date of lettuce was delayed for three or six weeks after EPTC application. EPTC controlled C. rotundus at half the dose that was required to control three species of annual grass that germinated near the soil surface. EPTC persisted longer when applied to air dry soil and incorporated with a rototiller than when incorporated into moist or wet soil.     

旱地燕麦间作对土壤酶活性、微生物含量及产量的影响

本文通过研究内蒙古旱作区禾本科、豆科及茄科间作对土壤生物性状的影响，旨在揭示燕麦（Avena sativa Linn）与不同作物间作及其单作在土壤酶活性、微生物量及土地当量比（LER）等方面的优势机理。本试验设置燕麦、黑豆（Glycinemax（L.）merr）、苜蓿（Medicago sativa）、马铃薯（Solanum tuberosum L）单作和黑豆间作燕麦、苜蓿间作燕麦、马铃薯间作燕麦共7个处理，探讨各处理对上述各指标的影响。结果表明：燕麦间作黑豆土地当量比最高，2015年和2016年分别为1.62和1.65。燕麦间作黑豆土壤脲酶活性和蔗糖酶活性较苜蓿间作燕麦、马铃薯间作燕麦显著提高了5.00%~51.61%和5.73%~52.29%。2015年和2016年播种后75 d苜蓿间作燕麦土壤过氧化氢酶活性显著高于黑豆间作燕麦，分别提高了29.47%和40.56%。黑豆间作燕麦对比其他两间作处理土壤微生物的生物量碳、氮含量分别显著提高了2.70%~17.89%和11.36%~26.47%，土壤脲酶活性提高了1.51%~55.22%，蔗糖酶活性提高了5.73%~52.29%，是该地区最优的间作模式。     

Characterization and Inhibitor Studies of Chitinases from a Parasitic Blowfly (Lucilia cuprina), a Tick (Boophilus microplus), an Intestinal Nematode (Haemonchus contortus) and a Bean (Phaseolus vulgaris)

The molecular weight pattern and the stage-specific activities of chitinases from the blowfly Lucilia cuprina, the tick Boophilus microplus and the intestinal nematode Haemonchus contortus were examined. Chitinolytic enzymes could be detected in all parasite species tested, but the activity was different between the stages. Highest chitinolytic titers were found in blowfly pupae (83 kDa, 118 kDa), hatching larvae of ticks (58 kDa, 94 kDa) and nematode eggs (43 kDa). Leaves from ethylene-treated bean plants Phaseolus vulgaris expressed two basic Class I chitinases (Ia, Ib) of 34 kDa, differing in their amino acid sequences at residue 33 and 34 (Ia: glycine, proline; Ib: lysine, aspartic acid). Inhibitor studies with blowfly pupae revealed that allosamidin (IC₅₀=0·32 (±0·02) μM ) was by far the best inhibitor when compared with various amino sugar derivatives. This compound also inhibited chitinases from tick larvae (IC₅₀=0·69(±0·10) μM ) and nematode eggs (IC₅₀=0·048(±0·0045) μM ) specifically. Whereas Class Ia chitinase from bean leaves was inhibited only up to 18% by 10 μM allosamidin, it had an IC₅₀ of 1(±0·14) μM for the Ib type, which is the first plant chitinase described to be highly sensitive to allosamidin.     

Selectivity factors relative to asulam for Senecio jacobaea L. control in Medicago sativa L. I. Retention,uptake and translocation*

Senecio jacobaea L. and Medicago sativa L. plants grown in a glasshouse were treated with foliar applications of aqueous solutions of asulam. Retention on foliage, uptake and translocation were measured in both species. Retention was greater in S. jacobaea than in M. sativa when no surfactant was added and similar when surfactant was added. Addition of surfactant modified spray distribution and increased asulam uptake in M. saliva but did not in S. jacobaea. S. jacobaea translocated over twice as much asulam from the treated area as M. sativa. These data suggest that surfactant should not be added for maximum selectivity. Differences in species response to asulam treatments are partially, but not entirely, explained by differences in retention, uptake and translocation.