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991.
Biao Liu Liang Wang Qing Zeng Jun Meng Wenjun Hu Xiaogang Li Kexin Zhou Kun Xue Doudou Liu Yangping Zheng 《Soil biology & biochemistry》2009,41(9):1841-1846
Transgenic insect-resistant cotton containing a synthetic version of the insecticidal toxin gene from Bacillus thuringiensis subsp. kurstaki has been planted in China in a large scale and may have adverse impacts on soil organisms. The leaves of the transgenic cotton and the non-transgenic parental cotton were collected and their impacts on the earthworm, Eisenia fetida, were tested in laboratory studies. No significant acute toxicity on E. fetida from oral exposure to the transgenic cotton line, GK19, was detected. The average weight, numbers of cocoons and new offsprings of E. fetida in the GK19 groups were all higher than in the Simian3 groups, but the differences were not significant. 相似文献
992.
Aidan M. Keith Rob W. Brooker Stephen J. Chapman René van der Wal 《Soil biology & biochemistry》2009,41(6):1060-1065
Trees have a key role in determining the composition of soil biota via both above and belowground resource-based mechanisms, and by altering abiotic conditions. We conducted an outdoor mesocosm experiment to investigate the relative impact of above and belowground tree inputs on soil nematode trophic composition, and examine whether tree-driven impacts differed between contrasting species (birch and pine). For both species, we created a factorial design of litter addition and root presence treatments. The litter addition treatment was equivalent to natural levels of litterfall; tree saplings were planted in mesocosms for the root presence treatment and an unplanted control treatment was established that had no litter or root inputs. Litter addition had a limited impact on soil nematode community composition: it primarily decreased omnivore and predatory nematode abundance in birch but had few other effects on the nematode community. By contrast, root presence markedly altered nematode community composition through changes in a range of trophic groups. For both birch and pine, there were significant increases in total, fungivore and predatory nematode abundance in root presence treatments, and furthermore, total and fungivore abundances were positively related to root biomass. Root presence of these contrasting tree species also had a distinctive impact on some specific nematode trophic groups; pine roots promoted bacterivore abundance while birch roots promoted root-hair feeding nematode abundance. These findings suggest strong bottom-up effects of belowground tree inputs, and indicate that particular components of the nematode community may be affected differently by resource quantity and quality. Consequently, we suggest that, in the short-term, belowground rather than aboveground tree inputs have a strong impact on soil food web structure and complexity. 相似文献
993.
T. Winkel J.P. Lhomme J.P. Nina Laura C. Mamani Alcn C. del Castillo A. Rocheteau 《Agricultural and Forest Meteorology》2009,149(10):1759-1768
Night radiative frost is a highly limiting factor for agriculture in Andean highlands. Nevertheless, a diversity of crop species have been domesticated there, commonly showing high heterogeneity in plant growth at the field level. The possible protective effect of crop canopy heterogeneity against nocturnal radiative frost is examined using a dual approach, combining a field experiment and a simplified energy balance model at the leaf level. Leaf and air temperatures were registered over an entire quinoa crop cycle in the Andean highlands of Bolivia, comparing two cultivars: Blanca de Yanamuyu, a traditional landrace with high plant height heterogeneity, and Surumi, a more homogeneous selected variety. In both cultivars, inverted air density profiles during calm and clear nights result in air temperature changes up to 3 °C over 0.5 m height, with minimum air temperature concentrated at the upper part of the canopy. In these conditions, leaf temperature gradients of up to 2.6 °C m−1 develop within the canopy of the traditional landrace, with minimum leaf temperature significantly higher (P < 0.001) in shaded plants of the landrace than in the selected cultivar. A dynamic model of leaf temperature based on canopy parameters and climatic records at screen level adequately simulates leaf temperature differences in the case of a vertically heterogeneous quinoa canopy. A sensitivity analysis of the model reveals that canopy height, leaf area index, and sky cloudiness have the most important influences on the development of the sheltering effect, while air temperature and air humidity play a minor role under typical radiative frost conditions. As for wind speed, its actual influence remains unclear due to experimental and modelling limitations at low wind speeds. The significance of these results is discussed in terms of the trade-off between stress adaptation and biomass productivity. 相似文献
994.
This study aims to determine leaf litter preference, consumption rate, growth rate, food conversion efficiency, and quality
of fecal pellets of two endemic pill millipedes (Arthrosphaera dalyi and Arthrosphaera davisoni) of the Western Ghats of India by laboratory microcosm experiments. Among seven combinations of three plantation leaf litters
offered in 4-day trial, top three preferred combinations were selected for 4-week trial. In 4-week trial, preference of mixed
litter diet was higher than single litter diet, which resulted in enhanced growth as well as food conversion efficiency of
millipedes. Among Hopea
,
Pongamia
, and Areca litters, A. dalyi preferred Hopea + Pongamia, and its consumption was significantly correlated with contents of organic carbon (P < 0.05; r = –0.97) and nitrogen (P < 0.01; r = 0.99), while growth rate with phosphorus content (P < 0.05; r = 0.97) and food conversion efficiency with contents of organic carbon (P < 0.05; r = 0.98) and calcium (P < 0.01; r = –0.99). Among Areca
,
Elettaria
, and Coffea litters, Areca + Elettaria
+ Coffea was most preferred by A. davisoni, which was significantly correlated with organic carbon content (P < 0.05; r = 0.98) and food conversion efficiency with calcium content (P < 0.0001; r = 0.99). The food conversion efficiency, however, was the highest in millipedes fed with Areca
+
Elettaria. The present study demonstrated increased nitrogen and phosphorus contents and decreased phenolic content and C/N ratio in
fecal pellets of pill millipedes fed with plantation litter, and thus, these millipedes play an important role in leaf litter
mineralization and soil enrichment in plantations Western Ghats. 相似文献
995.
996.
陕西省苜蓿茎点霉叶斑病病原菌的鉴定 总被引:1,自引:0,他引:1
近期发现了陕西省紫花苜蓿(Medicago sativa)一种苜蓿茎点霉叶斑病,为了准确鉴定该病害,开展了一系列病原鉴定试验。病叶片典型症状为叶尖上的深褐色斑点融合扩大呈“轮纹状”病斑;病原物的分生孢子无色透明,圆柱形,无隔单胞,大小为7×1.25 μm;以病原菌rDNA-ITS(核糖体DNA 内转录间隔区)序列的系统发育树的分析表明,病原菌与Phoma medicaginis var. Medicaginis(DQ109960)亲缘关系最近,NJ法中的相似性达到99%,UPGMA法中的相似性为98%;离体叶片接种验证病原菌具有致病性,结果表明:苜蓿茎点霉叶斑病的病原菌为苜蓿茎点霉(Phoma medicaginis var. Medicaginis)。 相似文献
997.
以绿绒海芋Alocasia micholitziana的叶片、叶柄为外殖体,研究不同灭菌剂对外殖体消毒效果的影响、不同激素及浓度配比的培养基对愈伤组织诱导、不定芽分化及增殖的影响。结果表明:(1)消毒处理时叶柄适于用0.1% HgCl2浸泡处理8 min,叶片则为7 min;(2)叶柄、叶片在所试培养基中均能诱导出愈伤组织,最佳诱导培养基为MS+2 mg/L 6-BA+2.0 mg/L 2,4-D+0.1 mg/L NAA,叶柄愈伤组织诱导率可达100%;(3)从愈伤组织诱导不定芽的最佳培养基为MS+2 mg/L 6-BA+0.4 mg/L NAA,诱导率可达100%;(4)在培养基MS+2 mg/L 6-BA+0.4 mg/L NAA上,芽增殖效果最佳,苗生长健壮;(5)最佳生根培养基为1/2MS+0.5 mg/L IBA,移栽后苗容易成活;(6)苗移栽时以泥炭土 ∶ 珍珠岩 ∶ 蛭石(3 ∶ 1 ∶ 1)成活率较高,可达98%以上,而且小苗生长健壮。 相似文献
998.
999.
不同浓度多效唑对晋遗31大豆农艺性状和产量的影响 总被引:3,自引:0,他引:3
于2010和2011年采用0、50、100、150、200、250、300、350 mg.kg-18个多效唑浓度对6片复叶期的晋遗31大豆进行叶面喷施。结果表明,50~350 mg.kg-1多效唑处理均表现增产,增产幅度2.22%~21.97%。其中以200mg.kg-1产量最高(4 175.40 kg.hm-2)。喷施多效唑后大豆株高和结荚高度明显降低,分枝增多,节间距缩短,百粒重、总荚数、单株重和单株粒重明显增加。综合分析,6片复叶期叶片喷施200 mg.kg-1多效唑能够有效改善农艺性状并提高大豆产量。 相似文献
1000.