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  • George, E  (58)
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  • 1
    Language: English
    In: Plant and Soil, 2013, Vol.364(1), pp.341-355
    Description: Aims: The aim was to quantify the nitrogen (N) transferred via the extra-radical mycelium of the arbuscular mycorrhizal fungus Glomus intraradices from both a dead host and a dead non-host donor root to a receiver tomato plant. The effect of a physical disruption of the soil containing donor plant roots and fungal mycelium on the effectiveness of N transfer was also examined. Methods: The root systems of the donor (wild type tomato plants or the mycorrhiza-defective rmc mutant tomato) and the receiver plants were separated by a 30 mu m mesh, penetrable by hyphae but not by the roots. Both donor genotypes produced a similar quantity of biomass and had a similar nutrient status. Two weeks after the supply of super(15)N to a split-root part of donor plants, the shoots were removed to kill the plants. The quantity of N transferred from the dead roots into the receiver plants was measured after a further 2 weeks. Results: Up to 10.6 % of donor-root super(15)N was recovered in the receiver plants when inoculated with the arbuscular mycorrhizal fungus (AMF). The quantity of super(15)N derived from the mycorrhizal wild type roots clearly exceeded that from the only weakly surface-colonised rmc roots. Hyphal length in the donor rmc root compartments was only about half that in the wild type compartments. The disruption of the soil led to a significantly increased AMF-mediated transfer of N to the receiver plants. Conclusions: The transfer of N from dead roots can be enhanced by AMF, especially when the donor roots have been formerly colonised by AMF. The transfer can be further increased with higher hyphae length densities, and the present data also suggest that a direct link between receiver mycelium and internal fungal structures in dead roots may in addition facilitate N transfer. The mechanical disruption of soil containing dead roots may increase the subsequent availability of nutrients, thus promoting mycorrhizal N uptake. When associated with a living plant, the external mycelium of G. intraradices is readily able to re-establish itself in the soil following disruption and functions as a transfer vessel.
    Keywords: Arbuscular mycorrhiza ; Reduced mycorrhizal colonisation (rmc) mutant ; Extra-radical mycelium ; Root turnover ; Solanum lycopersicum
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 2
    Language: English
    In: Plant and Soil, 2013, Vol.372(1), pp.361-374
    Description: Issue Title: In Memory of Horst Marschner This study aimed to determine the effect of arbuscular mycorrhizal (AM) fungi and phosphorus (P) supply levels on [beta]-carotene concentrations in sweet potato (Ipomoea batatas L.) tubers. Two commercial AM fungal isolates of Glomus intraradices (IFP Glintra) and Glomus mosseae (IFP Glm) which differ in their life cycles were used. Sweet potato plants were grown in a horizontal split-root system that consisted of two root compartments. A root-free fungal compartment that allowed the quantification of mycelial development was inserted into each root compartment. The two root compartments were inoculated either with the same or with different AM isolates, or remained free of mycorrhizal propagules. Each fungal treatment was carried out in two P supply levels. In the low P supply level, mycorrhizal colonization significantly increased [beta]-carotene concentrations in sweet potato tubers compared with the non-mycorrhizal plants. Glomus intraradices appeared to be more efficient in increasing [beta]-carotene concentrations than G. mosseae. Dual inoculation of the root system with the two mycorrhizal fungi did not result in a higher increase in tuber [beta]-carotene concentrations than inoculation with the single isolates. Improved P nutrition led to higher plant tuber biomass but was not associated with increased [beta]-carotene concentrations. The results indicate a remarkable potential of mycorrhizal fungi to improve [beta]-carotene concentrations in sweet potato tubers in low P fertilized soils. These results also suggest that [beta]-carotene metabolism in sweet potato tubers might be specifically activated by root mycorrhizal colonization.[PUBLICATION ]
    Keywords: β-carotene ; Glomus intraradices ; Glomus mosseae ; Phosphorus ; Sweet potato
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 3
    Language: English
    In: Food Chemistry, 2010, Vol.122(3), pp.566-571
    Description: Flavonoids have gained much attention because of their proposed positive effects for human health. Onions are a rich source of flavonoids, consisting mainly of the major flavonols quercetin-3,4′- -diglucoside (QDG) and quercetin-4′- -monoglucoside (QMG) in the bulb and the aglycone quercetin in the outer scales. In this study, distribution of these three flavonoids was determined in 16 onion cultivars ( ) using HPLC–DAD. Three different parts of the onion bulb, the inner layers, the middle layers and the outer scales were analysed. The analysis showed varietal differences in the selected onion cultivars. The cultivars with the highest total flavonoid content were the red skinned ‘Red Baron’ and the yellow skinned cultivars ‘Ailsa Craig’ and ‘Prilep’. The distribution of the total flavonoid content in the different parts of the onion bulb showed the following order: middle layers 〉 outer scales 〉 inner layers. In the inner layers QDG was the major flavonoid, while in the middle layers QDG and QMG were in equal amounts. In the outer scales quercetin was the major flavonoid prior to QMG.
    Keywords: Onions ; Allium Cepa ; Flavonoids ; Quercetin Glucosides ; Cultivars ; Profiling ; Chemistry ; Diet & Clinical Nutrition ; Economics
    ISSN: 0308-8146
    E-ISSN: 1873-7072
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  • 4
    Language: English
    In: Food Chemistry, 01 June 2014, Vol.152, pp.190-196
    Description: The decrease of water availability is leading to an urgent demand to reduce the plants’ water supply. This study evaluates the effect of topsoil drying, combined with varying sulfur (S) supply on glucosinolates in in order to reveal whether a partial root drying may already lead to a drought-induced glucosinolate increase promoted by an enhanced S supply. Without decreasing biomass, topsoil drying initiated an increase in aliphatic glucosinolates in leaves and in topsoil dried roots supported by increased S supply. Simultaneously, abscisic acid was determined, particularly in dehydrated roots, associated with an increased abscisic acid concentration in leaves under topsoil drying. This indicates that the dehydrated roots were the direct interface for the plants’ stress response and that the drought-induced accumulation of aliphatic glucosinolates is related to abscisic acid formation. Indole and aromatic glucosinolates decreased, suggesting that these glucosinolates are less involved in the plants’ response to drought.
    Keywords: 2-Propenyl Glucosinolate ; Topsoil Drying ; Abscisic Acid ; N:S Ratio ; Vegetable Mustard ; Chemistry ; Diet & Clinical Nutrition ; Economics
    ISSN: 0308-8146
    E-ISSN: 1873-7072
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  • 5
    Language: English
    In: Mycorrhiza, 2013, Vol.23(2), pp.107-117
    Description: Labeled nitrogen ( 15  N) was applied to a soil-based substrate in order to study the uptake of N by Glomus intraradices extraradical mycelium (ERM) from different mineral N (NO 3 − vs. NH 4 + ) sources and the subsequent transfer to cowpea plants. Fungal compartments (FCs) were placed within the plant growth substrate to simulate soil patches containing root-inaccessible, but mycorrhiza-accessible, N. The fungus was able to take up both N-forms, NO 3 − and NH 4 + . However, the amount of N transferred from the FC to the plant was higher when NO 3 − was applied to the FC. In contrast, analysis of ERM harvested from the FC showed a higher 15  N enrichment when the FC was supplied with 15 NH 4 + compared with 15 NO 3 − . The 15  N shoot/root ratio of plants supplied with 15 NO 3 − was much higher than that of plants supplied with 15 NH 4 + , indicative of a faster transfer of 15 NO 3 − from the root to the shoot and a higher accumulation of 15 NH 4 + in the root and/or intraradical mycelium. It is concluded that hyphae of the arbuscular mycorrhizal fungus may absorb NH 4 + preferentially over NO 3 − but that export of N from the hyphae to the root and shoot may be greater following NO 3 − uptake. The need for NH 4 + to be assimilated into organically bound N prior to transport into the plant is discussed.
    Keywords: Arbuscular mycorrhiza ; Cowpea ; Nitrate/ammonium transfer ; Fungal compartment
    ISSN: 0940-6360
    E-ISSN: 1432-1890
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  • 6
    Language: English
    In: Journal of the Science of Food and Agriculture, September 2011, Vol.91(12), pp.2234-2240
    Description: Food allergies are increasing in the European population. At present the onset of symptoms can be avoided only by elimination of a particular fruit or vegetable from the diet. A new approach is to develop hypoallergenic food products. This study characterises the allergenic potential of tomatoes, considering cultivation conditions, developmental stages and genotypes, in order to identify hypoallergenic fruits. Patients with a history of tomato allergy were recruited for skin allergy tests. Tomatoes carrying distinct genotypes were grown under various cultivation conditions and harvested at different maturation stages. Cultivation conditions (nitrogen fertilisation, light exposure and plant nutrition) did not affect the skin reactivity in tomato‐allergic patients. However, skin reactivity was significantly lower when using green‐unripe compared with red‐ripe tomatoes and when using landrace cultivars compared with cultivars bred for use in organic horticulture. Depending on their genetic background and maturity level, some tomato cultivars elicit positive reactions in tomato‐allergic patients in the skin allergy test. This novel finding should pave the way for the development of tomatoes with reduced allergenicity to relieve sufferers of tomato allergy. Copyright © 2011 Society of Chemical Industry
    Keywords: Food Allergy ; Tomato ; Cultivars ; Environmental Cultivation Conditions
    ISSN: 0022-5142
    E-ISSN: 1097-0010
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  • 7
    Language: English
    In: Scientia Horticulturae, 2011, Vol.130(3), pp.485-490
    Description: ► Three S levels, two NH :NO ratios, and AM fungi were tested on Chinese chive. ► Intermediate S was sufficient for optimal growth of . ► Increasing S concentration in the substrate increased organosulfur compounds. ► AM fungi decreased organosulfur compounds. ► Highest yield of organosulfur compounds was produced at NH :NO ratio of 50:50. Tissue concentrations of phytochemicals formed by species may be influenced by plant nutrient supply or rhizosphere microorganism activity. To test these relations, three plant nutritional factors were varied in two experiments with Chinese chive [ ]: (a) increasing sulfur concentrations in the substrate, (b) two ratios of ammonium to nitrate in supply, and (c) inoculation with arbuscular mycorrhizal (AM) fungi. Shoot dry weight, nutrient composition (nitrate, N, P, S), and organosulfur compounds (measured indirectly as pyruvic acid) were determined. In the first experiment, the supply of intermediate sulfur compared to low sulfur supply resulted in increased shoot dry weight and pyruvic acid concentrations. A further increase in sulfur supply increased plant pyruvic acid production in the absence of effects on dry weight. In the second experiment, AM fungi hardly increased shoot dry weight, nutrient, or pyruvic acid concentrations significantly. Pyruvic acid concentration was increased at an ammonium:nitrate ratio of 50:50 compared to a ratio of 5:95, whereas shoot dry weight was not significantly different. We conclude that both, supply of surplus sulfur or supply of equal amounts of ammonium and nitrate, can contribute to the production of high amounts of health related organosulfur compounds in Chinese chive.
    Keywords: Allium Tuberosum ; Am Fungi ; Ammonium ; Nitrate ; Organosulfur Compounds ; Sulfur ; Agriculture
    ISSN: 0304-4238
    E-ISSN: 1879-1018
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  • 8
    Language: English
    In: Soil Science Society of America journal, 2012, Vol.76(4), pp.1290-1300
    Description: Long-term use of organic soil amendments, compared with unamended or mineral fertilized soils, can change soil organic matter content, microbial biomass content, the microbial community structure, and the activity of enzymes involved in organic matter decomposition. It is not clear, however, whether long-term use of organic amendments, by means of these changes, leads to modified decomposition rates of newly added organic amendments. Therefore, this study was used to test the hypothesis that amendment history has an influence only on the decomposition of recalcitrant organic amendments and not on less recalcitrant organic amendments. Soils used for experimentation were taken from a field experiment where contrasting organic amendment regimes of farmyard manure, pine (Pinus sylvestris L.) bark, vegetable crop residues, and an unamended control had been applied for 35 yr. In a full factorial, laboratory-based incubation experiment, each soil was treated with each of these amendments and net C and N mineralization and microbial biomass C contents were monitored during a 147-d period. Collected data were then used to estimate gross turnover rates of newly added amendments with a modeling approach based on the soil organic matter module of the Daisy model. The modeling results suggested that the turnover of farmyard manure and pine bark, not however of crop residues, should be simulated in consideration of an amendment history effect. In contrast, the results of the ANOVA indicated that amendment history had an insignificant effect on net C and N mineralization from recently applied amendment. We concluded that the effects of amendment history on gross turnover rates of recently added organic amendments may depend on the type of amendment but that these effects on net C and N mineralization are minor in magnitude and hence irrelevant to N fertilization practice. ; p. 1290-1300.
    Keywords: Crop Residues ; Organic Soils ; Nitrogen Fertilizers ; Soil Organic Matter ; Organic Matter ; Field Experimentation ; Microbial Biomass ; Enzymes ; Vegetable Crops ; Models ; Soil Amendments ; Microbial Communities ; Pinus Sylvestris ; Bark ; Mineralization ; Analysis Of Variance ; Community Structure ; Animal Manures
    ISSN: 0361-5995
    E-ISSN: 14350661
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  • 9
    Language: English
    In: Journal of Plant Physiology, 2011, Vol.168(9), pp.911-919
    Description: The sucrose transporter functions in phloem loading of photoassimilates in solanaceous plant species. In the present study, wildtype and transgenic potato plants with either constitutive overexpression or inhibition of were grown under high or low phosphorus (P) fertilization levels in the presence or absence of the arbuscular mycorrhizal (AM) fungus . At a low soil P fertilization level, the extent of AM fungal root colonization was not different among the genotypes. In all plants, the AM symbiosis contributed significantly to P uptake under these conditions. In response to a high soil P fertilization level, all genotypes showed a decrease in AM fungal root colonization, indicating that the expression level of does not constitute a major mechanism of control over AM development in response to the soil P availability. However, plants with overexpression of showed a higher extent of AM fungal root colonization compared with the other genotypes when the soil P availability was high. Whether an increased symbiotic C supply, alterations in the phytohormonal balance, or a decreased synthesis of antimicrobial compounds was the major cause for this effect requires further investigation. In plants with impaired phloem loading, a low C status of plant sink tissues did apparently not negatively affect plant C supply to the AM symbiosis. It is possible that, at least during vegetative and early generative growth, source rather than sink tissues exert control over amounts of C supplied to AM fungi.
    Keywords: Arbuscular Mycorrhiza ; Carbohydrate Partitioning ; Phloem Loading ; Phosphorus Nutrition ; Sucrose Transporter Sut1 ; Botany
    ISSN: 0176-1617
    E-ISSN: 16181328
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  • 10
    Language: English
    In: Nutrient Cycling in Agroecosystems, 2011, Vol.91(3), pp.327-337
    Description: The nitrogen (N) use efficiency of field vegetable production systems needs to be increased in order to, reduce the detrimental effects of N losses on other ecosystems, save on production costs, and meet the limits set by the German government concerning N balance surpluses. Winter catch crops (CCs) have been shown to be a useful tool for reducing N losses in many agricultural production systems. This study was designed to test the effects of different CCs: rye ( Secale cereale L.), fodder radish ( Raphanus sativus L. var. oleiformis Pers.), bunch onion ( Allium cepa L.), and sudangrass ( Sorghum sudanense Stapf), planted at different sowing dates (early, late), on the N balance of 2-year vegetable crop rotation systems. The crop rotations started with a cauliflower ( Brassica oleracea L. var. botrytis L.) crop, which was fertilized with N in a conventional manner. The experiments took place at three different sites in Germany. Results revealed that the average N balance surplus, when taking into consideration, fertilization, soil mineral N, and aboveground plant biomass N, was 217 kg N ha −1 in the control treatments without a CC. This high value was mainly a consequence of large quantities of crop N and soil mineral N remaining after the harvest of the cauliflower. In spite of these high N surpluses, the application of CC only reduced the N balance surplus, on average across all sites and experiments, by 13 kg N ha −1 , when compared to the control treatments. The type of CC and the sowing date had only minor effects on the N balance. The findings of this study suggest that for many sites the application of CCs does not solve the problem of high N balance surpluses in intensive field vegetable production systems.
    Keywords: Catch crop ; Crop rotation ; Vegetable production ; Nitrogen losses ; Leaching ; Nitrogen balance
    ISSN: 1385-1314
    E-ISSN: 1573-0867
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