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41.
Predation by third instar larvae of Chrysoperla (=Chrysopa) carnea (Stephens) (Chrysopidae) did not alter the ratio of unparasitized Heliothis virescens (F.) (Noctuidae) larvae to H. virescens larvae parasitized by Microplitis croceipes (Cresson) (Braconidae) when these second instar larvae were exposed together to the predator on cotton (Gossypium hirsutum L., Malvaceae) in field cages. This indicates that C. carnea larvae did not prefer either parasitized or unparasitized larvae.
Prédation par Chrysopa carnea des chenilles d'Heliothis virescens parasitées par Microplitis croceipes
Résumé Les prédations de chenilles d'Heliothis virescens, parasitées ou saines, élevées sur coton (Gossypium hirsutum L.), de la variété Stoneville 213, ont été comparées, dans des cages de 10 m2 chacune placées dans la nature. Des chenilles du second stade ont été placées sur des pieds de coton dans 10 cages, à raison de 160 chenilles préalablement exposées à M. croceipes pendant leur premier stade et 40 chenilles saines par cage. Des larves du troisième stade de Chrysopa carnea ont été ajoutées dans 6 cages, à raison de 500/cage, et 4 cages ont servi de témoins pour évaluer les autres causes de mortalité. L'expérience a été répétée 2 fois. Les chenilles d'H. virescens ont été retirées au bout d'un jour dans une expérience et au bout de 2 jours dans l'autre. C. carnea n'a fait aucun choix entre chenilles parasitées ou non; la fréquence moyenne de chenilles parasitées n'a pas présenté de différence significative entre les cages avec ou sans C. carnea. Qui qu'il en soit, C. carnea a réduit significativement la survie des chenilles d'H. virescens parasitées ou non.相似文献
42.
E. Wada R. Imaizumi Y. Kabaya T. Yasuda T. Kanamori G. Saito A. Nishimune 《Plant and Soil》1986,93(2):269-286
Summary Plants from agricultural and natural upland ecosystem were investigated for15N content to evaluate the role of symbiotic N2-fixation in the nitrogen nutrition of soybean. Increased yields and lower δ15N values of nodulating soybeansvs, non-nodulating isolines gave semi-quantitative estimates of N2 fixation. A fairly large discrepancy was found between estimations by δ15N and by N yield at 0 kg N/ha of fertilizer. More precise estimates were made by following changes in plant δ15N when fertilizer δ15N was varied near15N natural abundance level. Clearcut linear relationships between δ15N values of whole plants and of fertilizer were obtained at 30 kg N/ha of fertilizer for three kinds of soils. In experimental
field plots, nodulating soybeans obtained 13±1% of their nitrogen from fertilizer, 66±8% from N2 fixation and 21±10% from soil nitrogen in Andosol brown soil; 30%, 16% and 54% in Andosol black soil; 7%, 77% and 16% in
Alluvial soil, respectively. These values for N2 fixation coincided with each corresponding estimation by N yield method.
Other results include: 1)15N content in upland soils and plants was variable, and may reflect differences in the mode of mineralization of soil organics,
and 2) nitrogen isotopic discrimination during fertilizer uptake (δ15N of plant minus fertilizer) ranged from −2.2 to +4.9‰ at 0–30 kg N/ha of fertilizer, depending on soil type and plant species.
The proposed method can accurately and relatively simply establish the importance of symbiotic nitrogen fixation for soybeans
growing in agricultural settings. 相似文献
43.
Review article number 6 : Plant molluscicides 总被引:1,自引:0,他引:1
A review on the application of plant molluscicides in the control of schistosomiasis is presented. Laboratory bioassays are discussed, together with criteria for activity. An attempt has been made to provide a comprehensive list of known molluscicidal natural products. 相似文献
44.
BioControl - Insects associated with the Sitka spruce weevil,Pissodes strobi (Peck), on Sitka spruce,Picea sitchensis (Bong.) Carr. were sampled at 9 locations in British Columbia. Fourteen species... 相似文献
45.
46.
George M. White 《Cell biochemistry and biophysics》1987,11(1):25-33
Computers, the human mind, and social systems have common problems of inadequate memory and insufficient data manipulation
speed. In each of these domains, information compression techniques have evolved to reduce storage and processing needs. Among
the techniques for information compression, coding of information in procedures stands out as exceptionally powerful. Procedural
information coding also gives rise to behavior that may be defined as intelligent. It is found in the human mind, in machines
and in social systems. Its use in human thought is aided by language development which promotes regular review of abstract
procedures. A practical consequence of better understanding of procedural information coding is the possibility of training
people to exhibit greater mental capacity, a controversial possibility. This paper explores the impact of data processing
resource limitations, data compression and procedural thinking in men and machines. 相似文献
47.
The effects of in vivo ultrasound irradiation of the spleen on immunological functions were assessed with an in vitro natural killer (NK) cell cytotoxic assay. Anesthetized hamsters were exposed to 1 MHz ultrasound at intensity levels currently being used clinically for therapeutic diathermy and hyperthermia (1-5 W/cm2, for 500 sec with constant beam scanning). Hyperthermic levels in the spleen ranged from 38-43 degrees C. Significant depression of natural killer (NK) cell activity was seen 4 h after spleen irradiation as compared to sham irradiated and normal animals. A return towards normal levels was observed in experimental groups at 24 h after exposure. Sham and normal animals were not significantly different in NK activity, indicating no significant stress-related immunosuppressive effects due to handling. Differential leukocyte counts taken for each exposure condition showed significant lymphopenia at 4, 8, and 16 h after exposure, near normal levels at 24 h, and complete recovery by 48 h. The number of circulating mononuclear cells at 4 h showed a dose-related suppression as the exposure intensities were increased. 相似文献
48.
Aluminum geochemistry in peatland waters 总被引:4,自引:4,他引:0
The chemical speciation of aluminum was examined in surface water samples from Sphagnum peatlands in north-central Minnesota, from peatlands along the Canadian east coast, and from bogs in the Pennine Mountain area of England. In highly organic ([DOC] 50 mg L–1 ), low pH waters, 80–90% of total dissolved Al was complexed with organic matter (OM), while in waters with low DOC ([DOC] 5 mg L–1) 54–86% of total dissolved Al existed as Al+3 or other inorganic Al species. Batch titrations of OM with Al revealed a high Al binding capacity, 1.4–2.8 mol (mg DOC)–1, that generally was unsaturated with Al. Titrations of OM with Al in conjunction with a continuous distribution model were used to determine Al-OM conditional stability constants. Binding capacity (mol Al (mg DOC)–1) and strength (formation constant) increased from pH 3 to 5 but decreased above pH 5 due to formation of AI-hydroxy species including A1(OH)3 (s). The high binding capacity of OM in bog waters facilitates metal mobility, especially in low pH (< 5) wetlands where metal solubility is high and OM concentrations are highest. Results showed that the relative degree of organic matter saturation with metal ions was important in modeling AI speciation in bog waters. 相似文献
49.
Bulk inorganic nitrogen deposition was monitored over a period of 3 years at the Bavella Pass (Corsica, France). Annual fluxes range between 126 and 150mol.m–2.d-–1, increasing slightly with annual rainfall. Natural background average concentrations of rain water and associated fluxes were estimated from a classification of rain events into natural (Oceanic and Saharan), polluted and composite. Long range transport of incoming polluted air masses increases the atmospheric wet nitrogen input by at least a factor of 1.6 in this Mediterranean area. Extrapolation of atmospheric dissolved inorganic nitrogen input to the Western Mediterranean leads to fluxes of 80 to l00mol.m–2.d-–1. This atmospheric input is in the same order of magnitude as the inorganic nitrogen riverine input. As a consequence, the nitrogen budget for the Mediterranean has had to be reassessed. Atmospheric wet inorganic nitrogen input is of noticeable importance to marine Mediterranean ecosystems, representing on average 10 to 25% of new production in the Western Basin, with values of up to 60% in oligotrophic zones. 相似文献
50.
James R. Griesemer 《Biology & philosophy》1990,5(1):3-36
Accounts of the relation between theories and models in biology concentrate on mathematical models. In this paper I consider
the dual role of models as representations of natural systems and as a material basis for theorizing. In order to explicate
the dual role, I develop the concept of a remnant model, a material entity made from parts of the natural system(s) under
study. I present a case study of an important but neglected naturalist, Joseph Grinnell, to illustrate the extent to which
mundane practices in a museum setting constitute theorizing. I speculate that historical and sociological analyses of institutions
can play a specific role in the philosophical analysis of model-building strategies. 相似文献