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  • 1
    Electronic Resource
    Electronic Resource
    Differences in the success of sugar maple and red maple seedlings on acid soils are influenced by nutrient dynamics and light environment (2005)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 28 (2005), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Variation in tolerance to nutrient limitations may contribute to the differential success of sugar maple (Acer saccharum Marsh.) and red maple (Acer rubrum L.) on acid soils. The objectives of this study were to examine these relationships as influenced by light environment and test whether sensitivity to nutrient stress is mediated by oxidative stress. First-year sugar maple and red seedlings were grown on forest soil cores contrasting in nutrient availability under high or low light intensity. Foliar nutrition, photosynthesis, growth and antioxidant enzyme activity were assessed. Photosynthesis and growth of sugar maple were significantly lower on nutrient-poor soils and were correlated with leaf nutrient status with Ca and P having the strongest influence. For red maple, only chlorophyll content showed sensitivity to the nutrient-poor soils. High light exacerbated the negative effects of nutrient imbalances on photosynthesis and growth in sugar maple. Antioxidant enzyme activity in sugar maple was highest in seedlings growing on nutrient-poor soils and was inversely correlated with photosynthesis, Ca, P, and Mg concentrations. These results suggest that: (1) sugar maple is more sensitive to nutrient stresses associated with low pH soils than red maple; (2) high light increases sugar maple sensitivity to nutrient stress; (3) the negative effects of nutrient imbalances on sugar maple may be mediated by oxidative stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2005.01337.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of manganese toxicity on leaf CO2 assimilation of contrasting common bean genotypes (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 101 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Parameters related to leaf photosynthesis were evaluated in three genotypes of common bean (Phaseolus vulgaris L.) with contrasting tolerance to Mn toxicity. Two short-term studies in solution culture were used to assess the effect of excess Mn on CO2 assimilation in mature and immature leaves. Mn toxicity decreased total chlorophyll content only in immature leaves, with a consequent reduction of leaf CO2 assimilation. Mature leaves that showed brown speckles characteristic of Mn toxicity, did not suffer any detriment in their capacity to assimilate CO2, at least in a 4-day experiment. Stomatal conductance and transpiration were not affected by the presence of high levels of Mn in leaf tissue. Lower stomatal conductance and transpiration rates were observed only in leaves with advanced chlorosis. Differences among genotypes were detected as increased chlorosis in the more sensitive genotype ZPV-292, followed by A-283 and less chlorosis in the tolerant genotype CALIMA. Since CO2 assimilation expressed per unit of chlorophyll was not different between high-Mn plants and control plants, we conclude that the negative effect of Mn toxicity on CO2 assimilation can be explained by a reduction in leaf chlorophyll content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb01076.x
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  • 3
    Electronic Resource
    Electronic Resource
    Ethylene and plant responses to nutritional stress (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 100 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Although ethylene is known to be involved in plant response to a number of biotic and abiotic stresses, relatively little is known concerning its role in nutritional stress arising from nutrient deficiency or mineral toxicity. There is clear evidence for involvement of ethylene in the symbiosis between Rhizobium and legumes, and in the ‘Strategy 1’ response to Fe deficiency. Ethylene may also be generated during tissue necrosis induced by severe toxicities and deficiencies. Metal toxicity may generate ethylene through oxidative stress. Evidence for a more general role for ethylene in regulating plant responses to macronutrient deficiency is suggestive but incomplete. Few studies have addressed this interaction, and most published reports are difficult to interpret because of the unrealistic way that nutrient treatments were imposed. Deficiency of N and P appear to interact with ethylene production and sensitivity. A role for ethylene in mediating adaptive responses to P stress is suggested by the fact that P stress can induce a variety of morphological changes in root systems that are also affected by ethylene, such as gravitropism, aerenchyma formation, and root hair development. Other adaptive responses include senescence or abscission of plant parts which cannot be supported by the plant. Ethylene and other plant hormones may be involved in mediating the stress signal to generate these responses. Although existing literature is inconclusive, we speculate that ethylene may play an important role in mediating the morphological and physiological plasticity of plant responses to nutrient patches in time and space, and especially root responses to P stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb03067.x
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  • 4
    Electronic Resource
    Electronic Resource
    Potassium transport in salt-stressed barley roots (1984)
    Springer
    Planta 161 (1984), S. 295-301 
    Details
    ISSN: 1432-2048
    Keywords: Hordeum ; Potassium transport ; Salt stress ; Xylem exudation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Salinization of the medium inhibits both K+ uptake by excised barley (Hordeum vulgare L.) roots and K+ release from their stele, as measured by short-term 86Rb uptake and xylem exudation, respectively. Although inhibition was not specific to chloride, mannitol caused a different response from that of inorganic sodium salts, indicating that inhibition was at least partly the result of an ion effect. In roots previously exposed to low levels of NaCl, NaCl stress directly affected stelar K+ release, whereas in low-sodium roots stelar K+ release was much less salt-sensitive than K+ uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00398718
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  • 5
    Electronic Resource
    Electronic Resource
    Modeling the belowground response of plants and soil biota to edaphic and climatic change—What can we expect to gain? (1994)
    Springer
    Plant and soil 165 (1994), S. 149-160 
    Details
    ISSN: 1573-5036
    Keywords: climate change ; CO2 enrichment ; modeling ; root biology ; soil biota
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract As atmospheric CO2 concentrations continue to increase, so too will the emphasis placed on understanding the belowground response of plants to edaphic and climatic change. Controlled-exposure studies that address the significance of an increased supply of carbon to roots and soil biota, and the consequences of this to nutrient cycling will play a prominent role in this process. Models will also contribute to understanding the response of plants and ecosystems to changes in the earth's climate by incorporating experimental results into conceptual or quantitative frameworks from which potential feedbacks within the plant-soil system can be identified. Here we present five examples of how models can be used in this analysis and how they can contribute to the development of new hypotheses in the areas of root biology, soil biota, and ecosystem processes. Two examples illustrate the role of coarse and fine roots in nitrogen and phosphorus uptake from soils, the respiratory costs associated with this acquisition of nutrients, and the significance of root architecture in these relationships. Another example focuses on a conceptual model that has helped raise new ideas about the effects of elevated CO2 on root and microbial biomass, and on nutrient dynamics in the rhizosphere. Difficulties associated with modeling the contribution of mycorrhizal fungi to whole-plant growth are also discussed. Finally, several broad-scale models are used to illustrate the importance of root turnover, litter decomposition, and nitrogen mineralization in determining an ecosystem's response to atmospheric CO2 enrichment. We conclude that models are appropriate tools for use both in guiding existing studies and in identifying new hypotheses for future research. Development of models that address the complexities of belowground processes and their role in determining plant and ecosystem function within the context of rising CO2 concentrations and associated climate change should be encouraged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009971
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  • 6
    Electronic Resource
    Electronic Resource
    Carbon cost of root systems: an architectural approach (1994)
    Springer
    Plant and soil 165 (1994), S. 161-169 
    Details
    ISSN: 1573-5036
    Keywords: carbon cost ; phosphorus ; Phaseolus vulgaris ; root architecture ; root growth ; root simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Root architecture is an important component of nutrient uptake and may be sensitive to carbon allocational changes brought about by rising CO2. We describe a deformable geometric model of root growth, SimRoot, for the dynamic morphological and physiological simulation of root architectures. Using SimRoot, and measurements of root biomass deposition, respiration and exudation, carbon/phosphorus budgets were developed for three contrasting root architectures. Carbon allocation patterns and phosphorus acquisition efficiencies were estimated for Phaseolus vulgaris seedlings with either a dichotomous, herringbone, or empirically determined bean root architecture. Carbon allocation to biomass, respiration, and exudation varied significantly among architectures. Root systems also varied in the relationship between C expenditure and P acquisition, providing evidence for the importance of architecture in nutrient acquisition efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009972
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  • 7
    Electronic Resource
    Electronic Resource
    Fractal geometry of root systems: Field observations of contrasting genotypes of common bean (Phaseolus vulgaris L.) grown under different phosphorus regimes (1998)
    Springer
    Plant and soil 206 (1998), S. 181-190 
    Details
    ISSN: 1573-5036
    Keywords: fractal geometry ; Phaseolus vulgaris L. (common bean) ; phosphorus deficiency ; phosphorus efficiency ; root architecture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Root growth and architecture are important for phosphorus acquisition due to the relative immobility of P in the soil. Fractal geometry is a potential new approach to the analysis of root architecture. Substantial genetic variation in root growth and architecture has been observed in common bean. Common bean (Phaseolus vulgaris L.) genotypes with contrasting root architecture were grown under moderate and low P conditions in a field experiment. Linear and planar fractal dimension were measured by tracing root intercepts with vertical planes. Linear fractal dimension increased over time in efficient genotypes, but remained fairly constant over time in inefficient genotypes. Planar fractal dimension increased over time for all genotypes, but was higher in efficient than inefficient genotypes at the end of the experiment. Planar fractal dimension of medium P plants was found to correlate with shoot P content indicating fractal dimension to be a possible indicator for root P uptake. The increasing fractal dimension over time indicates that fractal analysis is a sensitive measure of root branching intensity. A less destructive method for acquisition of data that allows for continuous analysis of fractal geometry and thereby screening for more P efficient genotypes in the field is suggested. This method will allow the researcher to conduct fractal analysis and still complete field trials with final yield evaluation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004499224717
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  • 8
    Electronic Resource
    Electronic Resource
    SimRoot: Modelling and visualization of root systems (1997)
    Springer
    Plant and soil 188 (1997), S. 139-151 
    Details
    ISSN: 1573-5036
    Keywords: computer modelling ; C programming language ; data structure ; fractal geometry ; kinematics ; root system ; visualization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract SimRoot, a geometric simulation model of plant root systems, is described. This model employs a data structure titled the Extensible Tree, which is well suited to the type of data required to model root systems. As implemented on Silicon Graphics workstations, the data structure and visualization code provides for continuous viewing of the simulated root system during growth. SimRoot differs from existing models in the explicit treatment of spatial heterogeneity of physiological processes in the root system, and by inclusion of a kinematic treatment of root axes. Examples are provided of the utility of the model in estimating the fractal geometry of simulated root systems in 1, 2, and 3 dimensional space. We envision continued development of the model to incorporate competition from neighboring root systems, linkage with crop simulation models to simulate root-shoot interactions, explicit treatment of soil heterogeneity, and plasticity of root responses to soil factors such as presence of mycorrhizal associations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004276724310
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  • 9
    Electronic Resource
    Electronic Resource
    The importance of root gravitropism for inter-root competition and phosphorus acquisition efficiency: results from a geometric simulation model (2000)
    Springer
    Plant and soil 218 (2000), S. 159-171 
    Details
    ISSN: 1573-5036
    Keywords: competition ; roots ; common bean ; mineral nutrition ; models ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We have observed that low soil phosphorus availability alters the gravitropic response of basal roots in common bean (Phaseolus vulgaris L.), resulting in a shallower root system. In this study we use a geometric model to test the hypotheses that a shallower root system is a positive adaptive response to low soil P availability by (1) concentrating root foraging in surface soil horizons, which generally have the highest P availability, and (2) reducing spatial competition for P among roots of the same plant. The growth of nine root systems contrasting in gravitropic response over 320 h was simulated in SimRoot, a dynamic three-dimensional geometric model of root growth and architecture. Phosphorus acquisition and inter-root competition were estimated with Depzone, a program that dynamically models nutrient diffusion to roots. Shallower root systems had greater P acquisition per unit carbon cost than deeper root systems, especially in older root systems. This was due to greater inter-root competition in deeper root systems, as measured by the volume of overlapping P depletion zones. Inter-root competition for P was a significant fraction of total soil P depletion, and increased with increasing values of the P diffusion coefficient (De), with root age, and with increasing root gravitropism. In heterogenous soil having greater P availability in surface horizons, shallower root systems had greater P acquisition than deeper root systems, because of less inter-root competition as well as increased root foraging in the topsoil. Root P acquisition predicted by SimRoot was validated against values for bean P uptake in the field, with an r 2 between observed and predicted values of 0.75. Our results support the hypothesis that altered gravitropic sensitivity in P-stressed roots, resulting in a shallower root system, is a positive adaptive response to low P availability by reducing inter-root competition within the same plant and by concentrating root activity in soil domains with the greatest P availability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1014987710937
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  • 10
    Electronic Resource
    Electronic Resource
    Estimating respiration of roots in soil: Interactions with soil CO2, soil temperature and soil water content (1997)
    Springer
    Plant and soil 195 (1997), S. 221-232 
    Details
    ISSN: 1573-5036
    Keywords: citrus ; Citrus volkameriana Tan. & Pasq. ; CO2-diffusion gradient ; root respiration ; soil CO2 concentration ; Volkamer lemon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Little information is available on the variability of the dynamics of the actual and observed root respiration rate in relation to abiotic factors. In this study, we describe I) interactions between soil CO2 concentration, temperature, soil water content and root respiration, and II) the effect of short-term fluctuations of these three environmental factors on the relation between actual and observed root respiration rates. We designed an automated, open, gas-exchange system that allows continuous measurements on 12 chambers with intact roots in soil. By using three distinct chamber designs with each a different path for the air flow, we were able to measure root respiration over a 50-fold range of soil CO2 concentrations (400 to 25000 ppm) and to separate the effect of irrigation on observed vs. actual root respiration rate. All respiration measurements were made on one-year-old citrus seedlings in sterilized sandy soil with minimal organic material. Root respiration was strongly affected by diurnal fluctuations in temperature (Q10 = 2), which agrees well with the literature. In contrast to earlier findings for Douglas-fir (Qi et al., 1994), root respiration rates of citrus were not affected by soil CO2 concentrations (400 to 25000 ppm CO2; pH around 6). Soil CO2 was strongly affected by soil water content but not by respiration measurements, unless the air flow for root respiration measurements was directed through the soil. The latter method of measuring root respiration reduced soil CO2 concentration to that of incoming air. Irrigation caused a temporary reduction in CO2 diffusion, decreasing the observed respiration rates obtained by techniques that depended on diffusion. This apparent drop in respiration rate did not occur if the air flow was directed through the soil. Our dynamic data are used to indicate the optimal method of measuring root respiration in soil, in relation to the objectives and limitations of the experimental conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004278421334
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