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P G Ayres - One of the best experts on this subject based on the ideXlab platform.
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responses of rust puccinia lagenophorae cooke to Nutrient Supply in groundsel senecio vulgaris l and effects of infection on host Nutrient relations
New Phytologist, 1990Co-Authors: Nigel D Paul, Aruna K Laxmi, P G AyresAbstract:Senecio vulgaris (groundsel), healthy or inoculated with rust (Puccinia lagenophorae), was grown in a Nutrient-poor sand-soil mixture amended with a compound fertiliser to provide a range of Nutrient regimes. The greatest number of pustules per plant occurred on unamended soil but fertiliser addition increased the sporulating area of each pustule: the leaf area occupied by pustules was unaffected by Nutrient Supply. Since total leaf area increased with increasing Nutrient Supply, the percentage of total area that was infected declined. Plant and root dry weights increased with Nutrient Supply and decreased with rust infection. Infection also reduced root fresh weight and length, which were little changed by Nutrient Supply, but reduced leaf area only under the most Nutrient-rich conditions. The ratios of root length: leaf area (R:L) and, especially, root:shoot dry weight (R:S) were reduced by infection. Root length per unit root weight was increased by infection when expressed on the basis of dry weight but not on the basis of fresh weight. Conversely, increasing Nutrient Supply decreased root length:weight only on the basis of fresh weight. The concentrations of P and K per unit dry weight were increased in rusted leaves but that of N was unchanged. Because infection increased the dry weight: fresh weight ratio (d. wt:f. wt) of leaves, concentrations of P and K on a fresh weight basis increased by up to 3-fold over those in controls and that of N was also substantially increased. On a dry weight basis, the concentration of N and K, but not P, increased in the roots of rusted plants. However, since d. wt:f. wt of roots was decreased in infected plants, the concentrations of N and K were unchanged on a fresh weight basis and that of P was significantly reduced. Rates of uptake of N, P and K were significantly increased in rusted plants both on the basis of root dry weight and root length. This was attributed to increased ‘shoot demand’ on each unit of root which, in turn, reflected the decreased R:S and R:L of infected plants.
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effects of interactions between Nutrient Supply and rust infection of senecio vulgaris l on competition with capsella bursa pastoris l medic
New Phytologist, 1990Co-Authors: Nigel D Paul, P G AyresAbstract:Senecio vulgaris L., either healthy or inoculated with rust (Puccinia lagenophorae Cooke), was grown in monoculture or in mixture with Capsella bursa-pastoris (L.) Medic, under high or low Nutrient conditions. At harvests made 7, 9, and 11 weeks after sowing, uninfected S. vulgaris progressively outcompeted C. bursa-pastoris under Nutrient-rich conditions. Rust infection eliminated the competitive advantage of S. vulgaris over C. bursa-pastoris under high Nutrient conditions. In contrast, under low Nutrient conditions C. bursa-pastoris outcompeted uninfected S. vulgaris and infection with P. lagenophorae resulted in no additional competitive disadvantage to its host. The reduced competitiveness of rusted S. vulgaris under high Nutrient conditions was associated with reductions in root growth in mixtures that were greater than those caused by rust in monocultures. The effects of Nutrient Supply, rust infection and competition on tissue concentrations of nitrogen, phosphorus and potassium were complex and often influenced by interactions between these factors. Increasing the Nutrient Supply increased nitrogen concentrations ([N]) in S. vulgaris, as did rust infection, but the effects of infection were confined to monocultures. In general [N] in C. bursa-pastoris showed rather less variation. Phosphorus concentrations ([P]) in C. bursa-pastoris increased with Nutrient Supply but under Nutrient-rich conditions were reduced by competition. In S. vulgaris [P] increased with increasing Nutrient Supply and with infection but in both cases responses were confined to monoculture. Potassium concentration ([K]) in S. vulgaris was increased by rust, especially in mixtures. In C. bursa-pastoris [K] under high Nutrient levels was higher in mixtures than in monoculture. The mechanisms by which the effects of rust on host competitiveness differed under high and low Nutrient conditions are considered and the implications for our understanding of the role of rusts in natural vegetation are discussed.
Nigel D Paul - One of the best experts on this subject based on the ideXlab platform.
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responses of rust puccinia lagenophorae cooke to Nutrient Supply in groundsel senecio vulgaris l and effects of infection on host Nutrient relations
New Phytologist, 1990Co-Authors: Nigel D Paul, Aruna K Laxmi, P G AyresAbstract:Senecio vulgaris (groundsel), healthy or inoculated with rust (Puccinia lagenophorae), was grown in a Nutrient-poor sand-soil mixture amended with a compound fertiliser to provide a range of Nutrient regimes. The greatest number of pustules per plant occurred on unamended soil but fertiliser addition increased the sporulating area of each pustule: the leaf area occupied by pustules was unaffected by Nutrient Supply. Since total leaf area increased with increasing Nutrient Supply, the percentage of total area that was infected declined. Plant and root dry weights increased with Nutrient Supply and decreased with rust infection. Infection also reduced root fresh weight and length, which were little changed by Nutrient Supply, but reduced leaf area only under the most Nutrient-rich conditions. The ratios of root length: leaf area (R:L) and, especially, root:shoot dry weight (R:S) were reduced by infection. Root length per unit root weight was increased by infection when expressed on the basis of dry weight but not on the basis of fresh weight. Conversely, increasing Nutrient Supply decreased root length:weight only on the basis of fresh weight. The concentrations of P and K per unit dry weight were increased in rusted leaves but that of N was unchanged. Because infection increased the dry weight: fresh weight ratio (d. wt:f. wt) of leaves, concentrations of P and K on a fresh weight basis increased by up to 3-fold over those in controls and that of N was also substantially increased. On a dry weight basis, the concentration of N and K, but not P, increased in the roots of rusted plants. However, since d. wt:f. wt of roots was decreased in infected plants, the concentrations of N and K were unchanged on a fresh weight basis and that of P was significantly reduced. Rates of uptake of N, P and K were significantly increased in rusted plants both on the basis of root dry weight and root length. This was attributed to increased ‘shoot demand’ on each unit of root which, in turn, reflected the decreased R:S and R:L of infected plants.
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effects of interactions between Nutrient Supply and rust infection of senecio vulgaris l on competition with capsella bursa pastoris l medic
New Phytologist, 1990Co-Authors: Nigel D Paul, P G AyresAbstract:Senecio vulgaris L., either healthy or inoculated with rust (Puccinia lagenophorae Cooke), was grown in monoculture or in mixture with Capsella bursa-pastoris (L.) Medic, under high or low Nutrient conditions. At harvests made 7, 9, and 11 weeks after sowing, uninfected S. vulgaris progressively outcompeted C. bursa-pastoris under Nutrient-rich conditions. Rust infection eliminated the competitive advantage of S. vulgaris over C. bursa-pastoris under high Nutrient conditions. In contrast, under low Nutrient conditions C. bursa-pastoris outcompeted uninfected S. vulgaris and infection with P. lagenophorae resulted in no additional competitive disadvantage to its host. The reduced competitiveness of rusted S. vulgaris under high Nutrient conditions was associated with reductions in root growth in mixtures that were greater than those caused by rust in monocultures. The effects of Nutrient Supply, rust infection and competition on tissue concentrations of nitrogen, phosphorus and potassium were complex and often influenced by interactions between these factors. Increasing the Nutrient Supply increased nitrogen concentrations ([N]) in S. vulgaris, as did rust infection, but the effects of infection were confined to monocultures. In general [N] in C. bursa-pastoris showed rather less variation. Phosphorus concentrations ([P]) in C. bursa-pastoris increased with Nutrient Supply but under Nutrient-rich conditions were reduced by competition. In S. vulgaris [P] increased with increasing Nutrient Supply and with infection but in both cases responses were confined to monoculture. Potassium concentration ([K]) in S. vulgaris was increased by rust, especially in mixtures. In C. bursa-pastoris [K] under high Nutrient levels was higher in mixtures than in monoculture. The mechanisms by which the effects of rust on host competitiveness differed under high and low Nutrient conditions are considered and the implications for our understanding of the role of rusts in natural vegetation are discussed.
Aruna K Laxmi - One of the best experts on this subject based on the ideXlab platform.
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responses of rust puccinia lagenophorae cooke to Nutrient Supply in groundsel senecio vulgaris l and effects of infection on host Nutrient relations
New Phytologist, 1990Co-Authors: Nigel D Paul, Aruna K Laxmi, P G AyresAbstract:Senecio vulgaris (groundsel), healthy or inoculated with rust (Puccinia lagenophorae), was grown in a Nutrient-poor sand-soil mixture amended with a compound fertiliser to provide a range of Nutrient regimes. The greatest number of pustules per plant occurred on unamended soil but fertiliser addition increased the sporulating area of each pustule: the leaf area occupied by pustules was unaffected by Nutrient Supply. Since total leaf area increased with increasing Nutrient Supply, the percentage of total area that was infected declined. Plant and root dry weights increased with Nutrient Supply and decreased with rust infection. Infection also reduced root fresh weight and length, which were little changed by Nutrient Supply, but reduced leaf area only under the most Nutrient-rich conditions. The ratios of root length: leaf area (R:L) and, especially, root:shoot dry weight (R:S) were reduced by infection. Root length per unit root weight was increased by infection when expressed on the basis of dry weight but not on the basis of fresh weight. Conversely, increasing Nutrient Supply decreased root length:weight only on the basis of fresh weight. The concentrations of P and K per unit dry weight were increased in rusted leaves but that of N was unchanged. Because infection increased the dry weight: fresh weight ratio (d. wt:f. wt) of leaves, concentrations of P and K on a fresh weight basis increased by up to 3-fold over those in controls and that of N was also substantially increased. On a dry weight basis, the concentration of N and K, but not P, increased in the roots of rusted plants. However, since d. wt:f. wt of roots was decreased in infected plants, the concentrations of N and K were unchanged on a fresh weight basis and that of P was significantly reduced. Rates of uptake of N, P and K were significantly increased in rusted plants both on the basis of root dry weight and root length. This was attributed to increased ‘shoot demand’ on each unit of root which, in turn, reflected the decreased R:S and R:L of infected plants.
Christian P G Iardina - One of the best experts on this subject based on the ideXlab platform.
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primary production and carbon allocation in relation to Nutrient Supply in a tropical experimental forest
Global Change Biology, 2003Co-Authors: Christian P G IardinaAbstract:Nutrient Supply commonly limits aboveground plant productivity in forests, but the effects of an altered Nutrient Supply on gross primary production (GPP) and patterns of carbon (C) allocation remain poorly characterized. Increased Nutrient Supply may lead to a higher aboveground net primary production (ANPP), but a lower total belowground carbon allocation (TBCA), with little change in either aboveground plant respiration (APR) or GPP. Alternatively, increases in Nutrient Supply may increase GPP, with the quantity of GPP allocated aboveground increasing more steeply than the quantity of GPP allocated belowground. To examine the effects of an elevated Nutrient Supply on the C allocation patterns in forests, we determined whole-ecosystem C budgets in unfertilized plots of Eucalyptus saligna and in adjacent plots receiving regular additions of 65kg Nha � 1 ,3 1kg Pha � 1 ,4 6kg Kha � 1 , and macro- and microNutrients. We measured the absolute flux of C allocated to the components of GPP (ANPP, TBCA and APR), as well as the fraction of GPP allocated to these components. Fertilization dramatically increased GPP. Averaged over 3 years, GPP in the fertilized plots was 34% higher than that in the unfertilized controls (3.95 vs. 2.95kg Cm � 2 yr � 1 ). Fertilization-related increases in GPP were allocated entirely aboveground ‐ ANPP was 85% higher and APR was 57% higher in the fertilized than in the control plots, while TBCA did not differ significantly between treatments. Carbon use efficiency (NPP/GPP) was slightly higher in the fertilized (0.53) compared with the control plots (0.51). Overall, fertilization increased ANPP and APR, and these increases were related to a greater GPP and an increase in the fraction of GPP allocated aboveground.
F Berendse - One of the best experts on this subject based on the ideXlab platform.
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soil acidity and Nutrient Supply ratio as possible factors determining changes in plant species diversity in grassland and heathland communities
Biological Conservation, 2000Co-Authors: W J Roem, F BerendseAbstract:To elucidate the causes of the sharp decline in plant species diversity in heathland and Nutrient-poor grasslands in The Netherlands, we investigated the spatial variation in plant species richness and the abundance of threatened plant species in relation to soil acidity and soil Nutrient Supply ratio. We selected 68 plots divided equally between species-rich and species-poor parts of the study area, and collected data on soil characteristics, above-ground biomass and vegetation composition in each plot. In addition, we used phytometers planted with Molinia caerulea tillers to measure the Nutrient Supply in the soil. Soil acidity was the variable most strongly correlated with plant species diversity in heathland and grassland communities. We found that increased N:P and N:K ratios in plant biomass had additional negative effects. The Red List species in the data set and all other species that had been declining sharply in the Netherlands since 1950 were growing in soils with pH >5 and most were growing in soils with balanced Nutrient Supply ratios.
