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51.
大麻叶蜂是安徽麻区大麻上的主要害虫之一.单食性,以幼虫咀食大麻叶片形成孔洞和缺刻,严重时仅残留叶柄和主叶脉,致使麻皮产量锐减.据室内饲养及结合田间定点观察,大麻叶蜂在安徽六安每年发生二代,以老熟幼虫于土内结茧越冬.两性或孤雌生殖,幼虫六龄、三龄前食量小,是药剂防治的有利时机,幼虫有趋嫩性和假死性. 室内测定和田间试验表明,喷洒杀螟松、乐果、西维因和敌敌畏1,000倍液,对三龄前幼虫有很好的效果,特别是杀螟松效果更佳,杀虫快速,药效期长,即使对高龄幼虫仍有良好的效果.  相似文献   
52.
Walking speeds of female Trichogramma exiguum Pinto & Platner were fastest on maize and soybean (12 cm/min), intermediate on tomato (8 cm/min), and slowest on woolly mullein, Verbascum thapsus (3 cm/min). Similarly, rates of turning along the paths of walking T. exiguum were smallest on maize (median angle=0°±15°), intermediate on soybean and tomato, and greatest on V. thapsus (median angle=30°±15°). Leaf trichome density and morphology influenced walking behavior. Walking was slowed and flight initiation delayed for T. exiguum walking on Amaranthus hybridus leaves compared to either maize or filter paper. When inundative releases are conducted, the effects of plant surfaces on searching rates and arrestment should be considered in determining release rates of Trichogramma spp.
Résumé La vitesse de marche a été déterminée en lâchant des individus sur chaque substrat végétal et en traçant leur parcours sur une plaque de verre placée à 9 mm au dessus du sujet. Les déviations angulaires de portions successives des tracés, longues de 1 mm, ont été utilisées pour mesurer les taux de changement de direction. Dans une deuxième expérience, des individus ont été lâchés au milieu d'une cercle de 40 mm de diamètre sur chaque substrat et les temps écoulés avant l'envol ou pour atteindre le bord du cercle à la marche ont servi à évaluer respectivement la propension au vol et la vitesse de déambulation.Les vitesses de marche ont été plus rapides sur maïs et soja (12 cm/min), moyennes sur tomate (8 cm/min) et les plus lentes sur Verbascum thapsus (Scrophulariaceae) (3 cm/min). De le même façon, les angles de changement de direction au cours des marches effectuées par T. exiguum ont été plus petits sur maïs, moyens sur soja et tomate, et plus grands sur V. thapsus. Chez T. exiguum marchant sur des feuilles d'Amaranthus hybridus L. (Amaranthaceae), la marche a été plus lente et l'envol plus tardif que sur maîs ou papier filtre.Lors de lâchers inondatifs, les effets des surfaces végétales sur les vitesses d'exploration et d'arrêt devraient être pris en compte pour déterminer les vitesses de lâcher des Trichogramma spp.
  相似文献   
53.
Summary Phenotypic models of selection are used to determine the effect of facultative parthenogenesis on the production of males in a spatially variable environment when (i) sex determination is under strict genetic control, and (ii) when sex may be environmentally determined. The results show that when sex is under strict genetic control and there is some chance of maturing in isolation, selection favors a female-biased sex ratio. When sex can be environmentally induced by cues which indicate high density, selection favors a mixture of genetic and environmental control, such that half the individuals always become female and the other half become females when isolated and become males when not isolated.  相似文献   
54.
Summary Dissociated single cells from chicken retina or tectum kept in rotation-mediated cell culture aggregate, proliferate and establish a certain degree of histotypical cellto-cell relationships (sorting out), but these systems never form highly laminated aggregates (nonstratified R- and T-aggregates). In contrast, a mixture of retinal plus pigment epithelial cells forms highly stratified aggregates (RPE-aggregates, see Vollmer et al. 1984). The present comparative study of stratified and nonstratified aggregates enables us to investigate the process of cell proliferation uncoupled from that of tissue stratification. Here we try to relate these two basic neurogenetic processes with patterns of expression of cholinesterases (AChE, BChE) during formation of both types of aggregates.During early aggregate formation, in both stratified and nonstratified aggregates an increased butyrylcholinesterase activity is observed close to mitotically active cells. Quantitatively both phenomena show their maxima after 2–3 days in culture. In contrast, AChE-expression in all systems increases with incubation time. In nonproliferative areas, in the center of RPE-aggregates, the formation of plexiform layers is characterized initially by weak BChE and then strong AChE-activity. These areas correspond with the inner (IPL) and outer (OPL) plexiform layers of the retina in vivo. Although by sucrose gradient centrifugation we find that the 6S- and the fiber-associated 11S-molecules of AChE are present in all types of aggregates, during the culture period the ratio of 11S/6S-forms increases only in RPE-aggregates, which again indicates the advanced degree of differentiation within these aggregates.It is thus demonstrated that cholinesterases first correlate with neuronal cell proliferation and later with stratification, which indicates functions of both enzymes during both developmental periods.Abbreviations AChE acetylcholinesterase - BChE butyrylcholinesterase - iso-OMPA specific inhibitor of BChE - BW 284C51 specific inhibitor of AChE - IPL inner plexiform layer - OPL outer plexiform layer  相似文献   
55.
56.
Heinz Müller 《Oecologia》1989,78(1):41-52
Summary During extensive field surveys in central and eastern Europe, 21 herbivorous root insect species were found on Centaurea maculosa ssp. rhenana Boreau, 12 species on C. diffusa Lam. and 11 species on C. vallesiaca Jordan, representing 12 families in 4 orders. The large geographic distribution (species-area function), the high number of Centaurea spp. present (host speciation rate), and the high apparency of the rosettes and the rich food resources offered by the roots during winter, together with their poor accessibility, correlate with the high number of specialist feeders associated with the roots of C. maculosa and C. diffusa. The members of the taxonomically diverse root entomofauna exploit specific structures of the tap root (food niches). Interspecific competition among members of food niches, as well as species-specific responses to different phenological stages (for oviposition) and tissues (for larval development) are thought to be responsible for the high predictability in guild structure. The relatively low levels of host plant attack (two thirds of the roots were unattacked) and the fact that food niches remained unoccupied in most of the regions suggest, however, that the majority of the studied guilds do not represent equilibrium assemblages. Ecological (different habitats), climatic (transitional zone) and historical (ancient pre-Pleistocene communities) factors could account for the highest values of species diversity, infestation levels, species packing and food niche utilization, which are found on C. maculosa in E. Austria/NW. Hungary, compared to other regions. A positive correlation between species packing (number of root-feeding species per population) and infestation rates (percent of roots attacked) was only found for the more stable, semi-natural habitats. A comparative analysis of the regional root insect guilds of C. maculosa with corresponding data for the phytophagous insects associated with the flower heads revealed distinct taxonomical differences, but a high degree of numerical and structural similarity. The different geographical regions are similarly ranked for host plant attack, herbivore pressure, average species packing and level of food niche utilization.  相似文献   
57.
Careful cutting of the hypocotyl of Ricinus communis L. seedlings led to the exudation of pure sieve-tube sap for 2–3 h. This offered the possibility of testing the phloem-loading system qualitatively and quantitatively by incubating the cotyledons with different solutes of various concentrations to determine whether or not these solutes were loaded into the sieve tubes. The concentration which was achieved by loading and the time course could also be documented. This study concentrated on the loading of sucrose because it is the major naturally translocated sieve-tube compound. The sucrose concentration of sieve-tube sap was approx. 300 mM when the cotyledons were buried in the endosperm. When the cotyledons were excised from the endosperm and incubated in buffer, the sucrose concentration decreased gradually to 80–100 mM. This sucrose level was maintained for several hours by starch breakdown. Incubation of the excised cotyledons in sucrose caused the sucrose concentration in the sieve tubes to rise from 80 to 400 mM, depending on the sucrose concentration in the medium. Thus the sucrose concentration in the sieve tubes could be manipulated over a wide range. The transfer of labelled sucrose to the sieve-tube sap took 10 min; full isotope equilibration was finally reached after 2 h. An increase of K+ in the medium or in the sieve tubes did not change the sucrose concentration in the sievetube sap. Similarly the experimentally induced change of sucrose concentration in the sieve tubes did not affect the K+ concentration in the exudate. High concentrations of K+, however, strongly reduced the flow rate of exudation. Similar results were obtained with Na+ (data not shown). The minimum translocation speed in the sieve tubes in vivo was calculated from the growth increment of the seedling to be 1.03 m·h-1, a value, which on average was also obtained for the exudation system with the endosperm attached. This comparison of the in-vivo rate of phloem transport and the exudation rate from cut hypocotyls indicates that sink control of phloem transport in the seedlings of that particular age was small, if there was any at all, and that the results from the experimental exudation system were probably not falsified by removal of the sink tissues.Abbreviations PTS 3-hydroxy-5,8, 10-pyrenetrisulfonate  相似文献   
58.
We have previously described in rat liver two protein kinases tightly bound to DNA, one is serine-specific, the other arginine-specific. In this work we show that both enzymes are present in various rat tissues and in liver from various species. Both kinase specific activities are strongly decreased in methyl-DBA-induced hepatomas and in HTC cells but not in regenerating liver after hepatectomy. This decrease is then not related to cell proliferation.  相似文献   
59.
Summary Innervation of the ascidian branchial basket and other structures is demonstrated by staining for cholinesterase. Cholinesterase activity is not restricted to synaptic sites but is present throughout the neurons. Primary and secondary axonal bundles form a bilaterally symmetric innervation pattern around the large dorsal visceral nerve. These bundles continue to split into progressively smaller bundles as they course throughout the basket. Axons are suspended in a fibrous matrix and run within the blood sinuses on the atrial side of the basket. Stigmatal ciliated cells of the branchial basket are innervated by highly branched distal portions of neurons, whose cell bodies are located in the ganglion. Synaptic boutons, containing electron-lucent vesicles, are found at nearly all stigmatal ciliated cells. NiCl2backfills of the visceral nerve reveal a distinct population of central neurons, some of which presumably control ciliary arrest.  相似文献   
60.
Cells of obligate methylotrophic Gram-negative bacterium Methylobacillus flagellatum KT which can only grow on methanol and methylamine media possess three different carriers mediating uptake of methylamin depending on growth conditions. All three uptake systems are energy-dependent, the methylamine uptake was inhibited by oxidative phosphorylation uncoupler and respiratory inhibitors. The first active transport system for methanol in the cells of obligate methylotroph was also demonstrated. The parameters of this system were measured, their dependence on energy, presence of respiratory inhibitors and uncoupler was shown.Abbreviations CCCP Carbonyl cyanide p-(trichloromethoxy)-phenylhydrazone - DCCD N,N-dicyclohexyl-carbodiimide  相似文献   
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