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排序方式: 共有82条查询结果,搜索用时 46 毫秒
1.
M. Sajjad Mirza Samina Mehnaz Philippe Normand Claire Prigent-Combaret Yvan Moënne-Loccoz René Bally Kauser A. Malik 《Biology and Fertility of Soils》2006,43(2):163-170
Nitrogen-fixing plant growth-promoting rhizobacteria (PGPR) from the genus Pseudomonas have received little attention so far. In the present study, a nitrogen-fixing phytohormone-producing bacterial isolate from kallar grass (strain K1) was identified as Pseudomonas sp. by rrs (16S ribosomal RNA gene) sequence analysis. rrs identity level was high with an uncharacterized marine bacterium (99%), Pseudomonas sp. PCP2 (98%), uncultured bacteria (98%), and Pseudomonas alcaligenes (97%). Partial nifH gene amplified from strain K1 showed 93% and 91% sequence similarities to those of Azotobacter chroococcum and Pseudomonas stutzeri, respectively. The effect of Pseudomonas strain K1 on rice varieties Super Basmati and Basmati 385 was compared with those of three non-Pseudomonas nitrogen-fixing PGPR (Azospirillum brasilense strain Wb3, Azospirillum lipoferum strain N4 and Zoogloea strain Ky1) used as single-strain inoculants. Pseudomonas sp. K1 was detected in the rhizosphere of inoculated plants by enrichment culture in nitrogen-free growth medium, which was followed by observation under the microscope as well as by PCR using a rrs-specific primer. For both rice varieties, an increase in shoot biomass and/or grain yield over that of noninoculated control plants was recorded in each inoculated treatment. The effect of Pseudomonas strain K1 on grain yield was comparable to those of A. brasilense Wb3 and Zoogloea sp. Ky1 for both rice varieties. These results show that nitrogen-fixing pseudomonads deserve attention as potential PGPR inoculants for rice. 相似文献
2.
During our screening of plant materials to find new natural fragrance and flavor ingredients, we discovered two series of 3-sulfanylalkyl alkanoates in a peel extract of fruits of wild-growing Poncirus trifoliata (L.) Raf. (Rutaceae), a species closely related to Citrus. The two series belong to alkanoates of 3-methyl-3-sulfanylbutan-1-ol and 3-sulfanylhexan-1-ol, respectively, and thus are members of a family of natural molecules having in common a 1,3-positioned O,S moiety. The alkanoate residues comprise all even-numbered saturated fatty acids from C2 (acetate) to C18 (octadecanoate). Among the 20 sulfur-containing compounds identified, 14 are described for the first time as naturally occurring in a botanical species. Several cysteine-S-conjugates were synthesized as hypothetical precursors of the new volatile sulfur-containing constituents, where after S-(3-hydroxy-1,1-dimethylpropyl)-L-cysteine, S-[3-(acetyloxy)-1,1-dimethylpropyl]-L-cysteine, and S-[1-(2-hydroxyethyl)butyl]-L-cysteine were identified in the fruit peel. No cysteine-S-conjugates were detected in the fruit juice. 相似文献
3.
Hugues Yvan Gomat Philippe Deleporte Régis Moukini Gladys Mialounguila Nina Ognouabi Aubin Rachel Saya Philippe Vigneron Laurent Saint-Andre 《Annals of Forest Science》2011,68(1):109-120
• Introduction
Stem taper equations have been widely used for volume estimation to varied top diameter limits or for biomass calculations. However, their main drawback is that specific calibration is often necessary for each species or clone, and accounting for genetic and environmental effects is often a challenge. 相似文献4.
Anat Lerner Ezekiel Baudoin Yvan Moenne-Loccoz Edouard Jurkevitch 《Soil biology & biochemistry》2006,38(6):1212-1218
Nucleic acid-based techniques allow the exploration of microbial communities in the environments such as the rhizosphere. Azospirillumbrasilense, a plant growth promoting rhizobacterium (PGPR), causes morphological changes in the plant root system. These changes in root physiology may indirectly affect the microbial diversity of the rhizosphere. In this study, the changes in the rhizobacterial structure following A. brasilense inoculation of maize (Zea mays) plants was examined by PCR-denaturating gradient gel electrophoresis (DGGE) and automated ribosomal intergenic spacer analysis (ARISA), using two universal primers sets for the 16S rRNA gene, and an intergenic 16S-23S rDNA primer set, respectively. Similar results were obtained when using either ARISA or DGGE performed with these different primer sets, and analyzed by different statistical methods: no prominent effect of A. brasilense inoculation was observed on the bacterial communities of plant roots grown in two different soils and in different growth systems. In contrast, plant age caused significant shifts in the bacterial populations. 相似文献
5.
Determination of the conjugated linoleic acids in cow's milk fat by Fourier transform Raman spectroscopy 总被引:1,自引:0,他引:1
Meurens M Baeten V Yan SH Mignolet E Larondelle Y 《Journal of agricultural and food chemistry》2005,53(15):5831-5835
The collective term "conjugated linoleic acid" or "CLA" generally refers to a mixture of conjugated positional and geometric isomers of linoleic (cis-9,cis-12-octodecadienoic) acid. In nature, these isomers are mainly formed in the rumen by biohydrogenation of polyunsaturated fatty acids. This study concerns a first trial of CLA determination in cow's milk fat by Raman spectroscopy. The spectra of pure cis-9-oleic, cis-9,cis-12-linoleic, cis-9,trans-11-linoleic, and trans-10,cis-12-linoleic acids have been examined in comparison with the spectra of selected milk-fat samples containing between 0 and 3% of CLA. The trial of CLA determination by Raman spectroscopy on cow milk fat has reached its objective with the two following results. First, the examination of the Raman spectra allows to identify three specific Raman signals of the chemical bonds associated to the cis,trans conjugated C=C in the rumenic and trans-10,cis-12-octodecadienoic acids at 1652, 1438, and 3006 cm(-1). Second, the calibration of Raman spectrometer for the CLA determination has indicated that these three specific signals suit very well for the accurate and reliable measurement of CLA concentration in milk fat. To our knowledge, the present study is the first successful attempt to determine the CLA content of milk fat by a spectrophotometric method. 相似文献
6.
Apolline Auclerc Johanne Nahmani Pierre Huguier Yvan Capowiez Delphine Aran François Guérold 《Pedobiologia》2011
Two laboratory experiments were carried out to determine the potential effects of lime application on the behavior of earthworms inoculated in an acidified forest soil from Vosges Mountains. Several field soils were studied: (i) a non-limed soil that had received decades of atmospheric acid depositions , (ii) an in situ limed soil that had been limed 6 years before at 2.5 t ha?1 and (iii) in vitro limed soils composed of non-limed soil mixed with several lime amounts in the laboratory corresponding to field rates of 1, 2.5, 5, 10 and 20 t ha?1. Firstly, we adapted the earthworm avoidance test (ISO, 2006) by using Eisenia fetida as the model organism and Lumbricus castaneus, a local species, to determine earthworm preference between non-limed and limed soils. Secondly, a cast production (CP) study was performed according to Capowiez et al. (2009) with Lumbricus terrestris, in seven different treatments (non-limed soil, in situ limed and five in vitro limed soils with pH from 5 to 6.3). Both species avoided the non-limed soil in favour of in situ and in vitro limed soils for both species. Results of the CP bioassay showed that the bioturbation behavior of L. terrestris significantly increased with the increase of soil pH, following a dose–response curve. However, in the long term (>6 years), the application of lime was insufficient to significantly improve soil conditions for enhancing earthworm activity. In conclusion, we may recommend this kind of earthworm laboratory tests with field soils to assess any changes in soil quality over time due to liming application. 相似文献
7.
BACKGROUND: Saponins are a class of secondary plant metabolites consisting of a sugar moiety glycosidically linked to a hydrophobic aglycone (sapogenin) that often possess insecticidal activities. Four saponins were selected: two triterpene saponins, Q. saponaria saponins and aescin, and two steroidal saponins, digitonin and diosgenin. Their effects were investigated on an important pest species and a model piercing‐sucking insect, the pea aphid Acyrthosiphon pisum. The triterpene Q. saponaria saponins bark saponin received special attention because of its high activity. Aphids were challenged by oral and contact exposure to demonstrate aphicidal activities, and in choice experiments to support use as a natural deterrent. RESULTS: When aphids were exposed to supplemented artificial diet for 3 days, a strong aphicidal activity was recorded for three of the four saponins, with an LC50 of 0.55 mg mL?1 for Q. saponaria saponins, 0.62 mg mL?1 for aescin and 0.45 mg mL?1 for digitonin. The LT50 values ranged between 1 and 4 days, depending on the dose. For diosgenin, only low toxicity (14%) was scored for concentrations up to 5 mg mL?1. In choice experiments with treated diet, a deterrence index of 0.97 was scored for Q. saponaria saponins at 1 mg mL?1. In contrast, direct contact showed no repellent effect. Spraying of faba bean plants with Q. saponaria saponins resulted in an LC50 of 8.2 mg mL?1. Finally, histological analysis in aphids fed with Q. saponaria saponins demonstrated strong aberrations of the aphid gut epithelium, and exposure of midgut CF‐203 cell lines to Q. saponaria saponins in vitro confirmed the cytotoxic effect. CONCLUSIONS: The present insect experiments provide strong evidence that saponins, as tested here with triterpene Q. saponaria saponins, can be useful as natural aphicides and deterrents. Furthermore, the insect midgut epithelium is suggested to be a primary target of saponin activity.Copyright © 2011 Society of Chemical Industry 相似文献
8.
9.
Episyrphus balteatus De Geer (Diptera: Syrphidae) is one of the most efficient biocontrol agents against Dysaphis plantaginea Passerini (Hemiptera: Aphididae) in apple orchards due to its early arrival. However, releasing flying predators in open orchards may be risky. We thus evaluated the combined effects of biological (early release of syrphids) and physical (Alt'Carpo nets) methods for controlling aphids under orchard conditions assuming that syrphids released under the nets will be able to survive and reproduce. Five experimental treatments containing two rows of trees each were set up in a pesticide-free orchard containing two different apple cultivars. For each cultivar, E. Balteatus adults were released (25, 40 and 90 adults per row) into three treatments, which were covered with nets, and two treatments were maintained free as controls (with and without nets). The releases, mainly in treatment 90, had a small effect on the development of the aphid population compared to netted control trees, especially towards the end of the study period when some of the differences were significant. This study demonstrated that E. balteatus adults can be successfully released under nets since we did observe an accumulation in the offspring of released individuals, mainly in treatments 40 and 90. 相似文献
10.
Exclusion nets aimed at controlling populations of the codling moth, Cydia pomonella are increasingly used in French apple orchards. The secondary effects of these so-called Alt’Carpo nets on other apple pests have not yet been thoroughly determined. This study was carried out to evaluate whether the presence of white nets (mesh size: 3 × 7.4 mm) affects the population dynamics of the rosy apple aphid (RAA), Dysaphis plantaginea and the abundance and composition of associated arthropod communities. We surveyed 50 infested shoots on a weekly basis throughout spring in 2008 and 2009 on apple trees with or without (control) nets in one insecticide-free orchard located in south-eastern France. At three dates in 2009, the RAA infestation rate was also computed by counting the total number of infested shoots per tree. The nets were installed at three different dates during the RAA lifecycle: September (September Netting Plot (SNP)), March (March Netting Plot (MNP)) and mid-April (April Netting Plot (ANP)). The abundance of RAA in the uncovered plot in 2008 was 1.75-fold higher than in the ANP. In 2009, this abundance was 1.39-fold higher than in the ANP and MNP, and slightly lower than in the SNP (1.07-fold). The nets (MNP and SNP) decreased the number of RAA colonies present in early spring. Interestingly, the nets reduced the duration of RAA infestation by 7–10 days. The highest reduction in RAA abundance and infestation rate was observed when nets were closed during the RAA development phase (ANP). The nets significantly reduced the abundance of ants on the marked shoots, especially in the ANP compared to the control. In addition, this study showed that nets have a significant negative influence on the abundance and richness of RAA-natural enemies. There was a significant decrease in the abundance of predators but no effect on the abundance of parasitoids. Syrphidae, Forficulidae and Coccinellidae were the most abundant natural enemy groups in the uncovered plot. Netting the plots led to a pronounced decrease in Coccinellidae abundance, a slight but significant decreased in Syrphids and had no effect on earwigs. Overall, Alt’Carpo exclusion nets had a direct negative impact on RAA population dynamics especially in the presence of at least one active natural enemy per marked shoot. These promising findings suggest that the combination of physical and biological control methods has potential for regulating RAA populations in organic orchards. 相似文献