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81.
Earthworm communities in conventional wheat monocropping and low-input wheat-clover intercropping systems 总被引:1,自引:0,他引:1
O SCHMIDT J P CURRY R A HACKETT G PURVIS R O CLEMENTS 《The Annals of applied biology》2001,138(3):377-388
A comparative study was conducted on earthworm communities in a conventional winter wheat monocropping system and a low‐input intercropping system in which successive crops of winter wheat were direct‐drilled into a permanent white clover sward. Earthworm abundance, biomass and species composition under the two cropping systems in the second and third years of successive cropping were assessed each spring and autumn in farm‐scale field plots at four sites using formalin and electrical extraction methods. The wheat‐clover cropping system supported larger earthworm communities (overall mean abundance 548 individuals m?2, 137 g biomass m?2) than conventional wheat monocropping (194 individuals m‐2, 36 g biomass m‐2). Between one and five more earthworm species were recorded in the wheat‐clover system than in the wheat system at three out of the four study sites. Wheat–clover cropping especially favoured species belonging to the epigeic and epigeic/anecic ecological groups such as Lumbricus castaneus, L. festivus, L. rubellus, juvenile Lumbricus and Satchellius mammalis. Earthworm communities in the wheat‐clover cropping system were comparable in size and species composition to communities normally found in perennial grassland‐type habitats such as pastures and grass‐legume leys. 相似文献
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Time course of signal transduction in phytochrome-mediated anthocyanin synthesis in mustard cotyledons 总被引:2,自引:2,他引:0
Abstract. The effectiveness of phytochrome (Pfr) in mediating anthocyanin synthesis in epidermal cells of mustard ( Sinupis alba L.) cotyledons is strongly increased by a light pretreatment of the seedling prior to competence (Mohr et al. , 1979; Johnson, 1980). Here we test the hypothesis that the observed 'sensitivity amplification' is related to a change in the time course of signal transduction from phytochrome to the responsive cell function. It was found that the time course of escape from photoreversibility—considered to reflect the time course of signal transduction—is not changed by a light pretreatment, although the rate of signal transduction increases with age and depends strongly on the level of Pfr. 相似文献
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ERWIN BECK MARGOT SENSER RENATE SCHEIBE HANS-MARTIN STEIGER PAUL PONGRATZ 《Plant, cell & environment》1982,5(3):215-222
Abstract. The large leaf rosettes of the so-called 'giant rosette' plants which inhabit the alpine region of tropical mountains are composed of a great number of adult leaves surrounding a central cone of developing leaves. Upon onset of the nocturnal frost period the adult leaves nyctinastically bend inwards and form a night-bud around the central leaf bud. The insulating effect of the night-bud was analysed in four species: Senecio keniodendron, Senecio brassica. Lobelia keniensis and Lobelia telekii which grow on Mt Kenya (Kenya). Freezing is avoided by a delay of cooling which is sufficient until rewarming by the next day's sunshine. A consequence of this delay is that the temperature in the nocturnal bud remains higher than that of the outer leaves which are often stiffly frozen after cold nights. Only one freezing point was detected on the leaf temperature recordings. Depending on the water state, the freezing points were in the range — 1°C to —4.2°C. Sucrose, amounting to 38% of the leaf dry weight, may act as a cryoprotectant for the cell membranes. Frost hardiness of the leaves, as determined with a laboratory method, was sufficient to enable the plants to survive during the nocturnal frost temperatures as measured in the field. 相似文献
85.
SERGEI I. FOKIN THORSTEN STOECK HELMUT J. SCHMIDT 《The Journal of eukaryotic microbiology》1999,46(4):416-426
Paramecium nephridiatum Gelei. 1925, was rediscovered. It is a euryhaline brackish-water species that morphologically resembles Paramecium woodruffi . but with multiple contractile vacuole pores. The general morphology, morphometry. and random amplified polymorphic DNA (RAPD) fingerprint patterns are presented for a number of the stocks collected around the world. 相似文献
86.
The development of taurine uptake into the unicellular greenalga Chlorella fusca 211-8b was characterized as a specificresponse to either nitrate or sulphate limitation. Taurine transportunder nitrogen starvation was stimulated by low pH and showeda biphasic kinetics with Km-values of 1.1 x 103 mol dm3and 1.0 x 102 mol dm3. Uptake was substantiallyinhibited by all - and ß-amino acids tested, whereassulphonate analogues failed to diminish taurine accumulation.Thus, uptake seemed to be mediated by a general aminoacid permease, unable to discriminate between carboxyland sulphonyl groups. However, Chlorella fusca could not catabolizethis unusual ß-amino acid and mobilize the amino-boundnitrogen for growth. Only a small group of -amino acids supportedthe growth of Chlorella fusca as an efficient nitrogen source. Key words: Taurine uptake, nitrogen starvation, amino acid uptake, Chlorella fusca. 相似文献
87.
Development of a dot immunobinding assay to detect Phytophthora spp. in naturally dark-rooted woody plants 总被引:1,自引:0,他引:1
An indirect dot immunobinding assay (DIBA) with a PAb raised against an isolate of P. cinnumomi was evaluated to detect Phytophthora spp. in naturally dark-rooted woody plants. Screening of different modifications of the procedure were done with root samples of Chamaecyparis lawsoniana non-infected and infected with P. cinnamomi. With the optimised DIBA procedure, root infection could be diagnosed by a clearly defined halo around the spot and by a colour change in the spot using Fast Red or Fast Blue substrate. Detection of different Phytophthora species in Chamaecyparis plants from commercial nurseries was successful with the optimised procedure. 相似文献
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