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  • Articles  (16)
  • roots  (16)
  • 2000-2004  (16)
  • 1950-1954
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  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (16)
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  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (16)
  • Architecture, Civil Engineering, Surveying
  • Biology  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Physiological and Cytological Studies on the Inhibition of Striga Seed Germination by the Plant Growth-promoting Bacterium Azospirillum brasilense (2000)
    Springer
    European journal of plant pathology 106 (2000), S. 347-351 
    Details
    ISSN: 1573-8469
    Keywords: exudate ; lipophilic ; parasite ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Striga hermonthica (Del.) Benth. is an obligate parasitic weed of tropical cereals whose rhizosphere can also be colonised by bacteria of the genus Azospirillum. A previous study demonstrated that the two organisms (Azospirillum and striga) interacted during cerealroot colonisation. Two strains of A. brasilense isolated from an African sorghum rhizosphere prevented the germination of striga seeds although they were stimulated to germinate by the presence of sorghum roots. Azospirillum cells suspended in a synthetic germination stimulant (GR24) did not inhibit striga seed germination, but did block radicle elongation. Those radicles had an abnormal morphology, and contained no vacuolated cells in the root elongation zone. Lipophilic compounds extracted from the medium of bacteria in the log and stationary growth phases prevented the germination of striga seeds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008734609069
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  • 2
    Electronic Resource
    Electronic Resource
    Urban tree root systems and their survival near houses analyzed using ground penetrating radar and sap flow techniques (2000)
    Springer
    Plant and soil 219 (2000), S. 103-116 
    Details
    ISSN: 1573-5036
    Keywords: Acer campestre ; clay soils ; ground penetrating radar ; roots ; sap flow ; water consumption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Root systems of two mature Field maple trees (Acer campestre L.) growing in both shaded and non-shaded sites, on clay soil in an urban environment, were analyzed by ground penetrating radar (GPR), light microscope and sap flow techniques. The ground surface above the root systems was covered by asphalt. However, a small piece of garden existed near the non-shaded tree, and root area of roots growing in this direction increased significantly, due to a presumed increase in available water and nutrients. However, no garden was present near the shaded tree, therefore roots remaining under the asphalt surface did not increase in area in any particular direction. Maximum rooting depth of shaded and exposed trees, as determined by GPR, was approximately 1.4 and 1.7 m, respectively. The trees utilized relatively large amounts of water for transpiration, i.e. 65–140 l per fine summer day and in average 10 m3 per growing season. However, transpiration expressed per root surface area (and/or whole root system enveloping area) was practically the same in both trees, i.e. 1 dm3 m-2 d-1 or almost 100 dm3 m-2 per growing season. These figures represented about 50% of potential evapotranspiration when considering projected crown areas. Increased transpiration under long-term high evaporation demands may cause occasional local drying of soil around roots, associated with soil shrinking in clay, which can be followed by serious damage to buildings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004736310417
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  • 3
    Electronic Resource
    Electronic Resource
    A rhizolysimeter facility for studying the dynamics of crop and soil processes: description and evaluation (2000)
    Springer
    Plant and soil 223 (2000), S. 89-99 
    Details
    ISSN: 1573-5036
    Keywords: experimental facility ; lysimeters ; minirhizotrons ; roots ; soil dynamic processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An experimental facility was designed to study simultaneously soil and shoot processes in agricultural crop systems. The facility is composed of 48 drainage lysimeters, from which 24 can be in use at the same time. These were equipped with horizontal minirhizotrons (for non-destructive root observation), suction cups (to sample the soil solution), thermistors (for the control and monitoring of the temperature), time-domain reflectometry (TDR) probes (to control and measure the volumetric soil water content) and leachate samplers (to measure the leachate and to monitor nutrient leaching). Together with non-destructive shoot data measurements, the instrumentation can be used to study the dynamics of above- and below-ground crop growth, as well as the leaching of nutrients (like nitrate) and the water budget. The results of a 1-year maize (Zea mays L.) experiment, in which shoot growth and development were compared to root growth, nitrogen and water dynamics, are presented. Maximum leaf area and maximum root density were well synchronized in the upper soil horizons, while in deeper horizons time of maximum root density was delayed. Nitrate leaching was high throughout the season, always exceeding the ‘safe limit’ for drinking water (10 mg l-1). It was especially high during early season, exceeding the rather tolerant ‘EC limit’ for drinking water (50 mg l-1). As a consequence, 90% of the nitrogen leaching losses were observed within 50 days after planting. Intensive water percolation followed high precipitation early in the crop season. At the end of the crop season, water percolation lagged behind precipitation, as soil water content replenished. The intensive growth of the shoot up to tasseling is reflected by the extensive exploitation of soil water reserves. The coincidence of minimum soil water storage and maximum leaf area, as well as the maximum rooting density in the upper soil layers, is remarkable and demonstrates the close relationship between demand (shoot activity), supply (root activity) and the exploration of soil water reserves. The facility was demonstrated to be suitable for the investigation of complex interactions between two plant components (shoots and roots) and between the plants and the environment, as are expected to occur during the growth of an agricultural crop. It will be most useful to evaluate present and alternative agronomic strategies in relation to their environmental feasibility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004825814002
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  • 4
    Electronic Resource
    Electronic Resource
    Root dynamics in a semi-natural grassland in relation to atmospheric carbon dioxide enrichment, soil water and shoot biomass (2000)
    Springer
    Plant and soil 223 (2000), S. 255-265 
    Details
    ISSN: 1573-5036
    Keywords: Elevated CO2 ; minirhizotrons ; open-top chambers ; roots ; soil moisture ; water-use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Plant responses to increasing atmospheric CO2 concentrations have been studied intensively. However, the effects of elevated CO2 on root dynamics, which is important for global carbon budgets as well as for nutrient cycling in ecosystems, has received much less attention. We used minirhizotrons inside open-top chambers to study the effects of elevated atmospheric carbon dioxide concentration on root dynamics in a nutrient-poor semi-natural grassland in central Sweden. We conducted our investigation over three consecutive growing seasons during which three treatments were applied at the site: Elevated (≈ 700 μmol mol-1) and ambient (≈ 360 μmol mol-1) chamber levels of CO2 and a control, without a chamber. During 1997, a summer with two dry periods, the elevated treatment compared with ambient had 25% greater mean root counts, 65% greater above-ground biomass and 15% greater soil moisture. The chambers seemed responsible for changes in root dynamics, whereas the elevated CO2 treatment in general increased the absolute sum of root counts compared with the ambient chamber. In 1998, a wet growing season, there were no significant differences in shoot biomass or root dynamics and both chamber treatments had lower soil moisture than the control. We found that as seasonal dryness increased, the ratio of elevated – ambient shoot biomass production increased while the root to shoot ratio decreased. We conclude that this grasslands response to elevated CO2 is dependent on seasonal weather conditions and that CO2 enrichment will most significantly increase production in such a grassland when under water stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004801718567
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructural effects of the herbicide chlorpropham (CIPC) in root tip cells of wheat (2000)
    Springer
    Plant and soil 226 (2000), S. 11-19 
    Details
    ISSN: 1573-5036
    Keywords: Chlorpropham (CIPC) ; microtubules ; nuclei ; recovery ; roots ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The present ultrastructural investigation on the effects of 50 μM chlorpropham (previously called CIPC) on growing roots of wheat (Triticum aestivum (L.) Thell cv. Vergina) was undertaken to clarify the mechanism of a carbamate herbicide action in plant cells, since the wide range of responses of plant cells to carbamate herbicides is based mainly on immunofluorescence studies. Cells of control roots contained abundant microtubules both in interphase and mitotic arrays. In chlorpropham-treated roots, however, no microtubules could be detected at all, neither in dividing nor in differentiating cells. Cycling cells became binucleate, polyploid or contained incomplete cell walls, the result of inhibition of cytokinesis. In long-term drug treatments (24 h or more) the affected cells entered a new cycle, which, however, did not progress beyond mid-metaphase. The nuclei of binucleate cells initiated prophase synchronously. Small vacuoles and Golgi vesicles were trapped within the nucleoplasm of the multilobed nuclei. In roots recovering from 8 h chlorpropham treatment, cells continued to exhibit polyploid nuclei, intranuclear vacuoles and incomplete walls. Microtubules reappeared but they were sparse and lacked a definite orientation. Preprophase cells did not form normal preprophase bands of microtubules, while mitotic cells occasionally contained microtubules bound to chromosomes and converged to minipoles. It is concluded that chlorpropham disorganized directly microtubules in addition to irreversibly affecting microtubule organizing centres, which failed to further support microtubule arrays.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026409027223
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  • 6
    Electronic Resource
    Electronic Resource
    Metal-binding capacity of arbuscular mycorrhizal mycelium (2000)
    Springer
    Plant and soil 226 (2000), S. 227-234 
    Details
    ISSN: 1573-5036
    Keywords: Biomass ; biosorption ; heavy metals ; fungi ; rhizosphere ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Experiments with excised mycelium of several Glomus spp. with different histories of exposure to heavy metals were carried out to measure their capacities to bind Cd and Zn. Cd sorption was followed for up to 6 h of incubation to determine its time course relationships. Controls treated with a metabolic inhibitor were included to evaluate whether sorption was due to active uptake or passive adsorption. The effect of ion competition (effects of Ca or Zn on Cd sorption) and general measurements of cation exchange capacity (CEC) of roots and hyphae were also performed. The results showed that AM mycelium has a high metal sorption capacity relative to other microorganisms, and a CEC comparable to other fungi. Metal sorption was rapid (〈30 min) and appeared mainly to be due to passive adsorption. Adsorption was highest in a metal-tolerant G. mosseae isolate and intermediate for a fungus isolated from a soil treated with metal-contaminated sludge. The former adsorbed up to 0.5 mg Cd per mg dry biomass, which was three times the binding capacity of non-tolerant fungi, and more than 10 times higher than reported values for, e.g., the commonly used biosorption organism Rhizopus arrhizus. The implications of these results for AM involvement in plant protection against excess heavy metal uptake are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026565701391
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  • 7
    Electronic Resource
    Electronic Resource
    Allocation of carbon to shoots, roots, soil and rhizosphere respiration by barrel medic (Medicago truncatula) before and after defoliation (2000)
    Springer
    Plant and soil 227 (2000), S. 67-75 
    Details
    ISSN: 1573-5036
    Keywords: carbon ; 13C ; 14C ; defoliation ; partitioning ; pasture legumes ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The allocation of carbon to shoots, roots, soil and rhizosphere respiration in barrel medic (Medicago truncatulaGaertn.) before and after defoliation was determined by growing plants in pots in a labelled atmosphere in a growth cabinet. Plants were grown in a 14CO2-labelled atmosphere for 30 days, defoliated and then grown in a 13CO2-labelled atmosphere for 19 days. Allocation of 14C-labelled C to shoots, roots, soil and rhizosphere respiration was determined before defoliation and the allocation of 14C and 13C was determined for the period after defoliation. Before defoliation, 38.4% of assimilated C was allocated below ground, whereas after defoliation it was 19.9%. Over the entire length of the experiment, the proportion of net assimilated carbon allocated below ground was 30.3%. Of this, 46% was found in the roots, 22% in the soil and 32% was recovered as rhizosphere respiration. There was no net translocation of assimilate from roots to new shoot tissue after defoliation, indicating that all new shoot growth arose from above-ground stores and newly assimilated carbon. The rate of rhizosphere respiration decreased immediately after defoliation, but after 8 days, was at comparable levels to those before defoliation. It was not until 14 days after defoliation that the amount of respiration from newly assimilated C (13C) exceeded that of C assimilated before defoliation (14C).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026599229920
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  • 8
    Electronic Resource
    Electronic Resource
    Screening the ability of rice roots to overcome the mechanical impedance of wax layers: importance of test conditions and measurement criteria (2000)
    Springer
    Plant and soil 219 (2000), S. 187-196 
    Details
    ISSN: 1573-5036
    Keywords: mechanical impedance ; Oryza sativa ; rice ; roots ; screening ; wax layers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The development of a wax layer method for screening the ability of rice (Oryza sativa L.) roots to overcome mechanical impedance is described. Wax layers (3 mm thick) made of mixtures of white soft paraffin and paraffin wax were installed 50 mm deep in tubes of sand. The sand was watered with nutrient solution and planted with 3-d old rice seedlings. The numbers of root axes per plant that had penetrated the wax layers 24 d after planting were counted. The ratio of penetrated to total root axes per plant gave a misleading measure of root penetration ability, as rice varieties differed in the ratio of penetrated to total axes in a low impedance (3% wax) control. In non-flooded conditions, a 60% wax layer decreased root penetration (number of roots penetrating the wax layer per plant) to a mean of 74% of the low impedance control, whereas an 80% wax layer decreased mean root penetration to 31% of the control. The best measure of root penetration in non-flooded conditions was the number of axes penetrating an 80% wax layer. Flooding decreased root penetration of a 60% wax layer to a mean of 26% of the low impedance control. The best measure of root penetration in flooded conditions was the number of axes penetrating a 60% wax layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004753900945
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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
    Root growth of cauliflower (Brassica oleracea L. botrytis) under unstressed conditions: Measurement and modelling (2000)
    Springer
    Plant and soil 223 (2000), S. 133-147 
    Details
    ISSN: 1573-5036
    Keywords: Cauliflower ; dry matter production ; model ; minirhizotron method ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Root observations were carried out on cauliflower using the minirhizotron and the soil core method in two years on two locations with different soil types, a loess loam and a humic loamy sand. Total root length (RL) (cm cm-2) of cauliflower was correlated to total shoot dry weight (Wsh) (g m-2) RL=0.0124(±0.005)s*Wsh, r2=0.76. There was an acceptable correlation (r2=0.88) between the minirhizotron and the soil core methods for the sub-soil data, whereas the minirhizotron method underestimated rooting intensity for the top soil. Changes in rooting depth over time could be described for both soil types using a segmented function of temperature sum, consisting of an early exponential and a later linear phase. The increase of rooting depth during the linear phase was 0.107(±0.01) cm °C-1 d-1. A simple descriptive root growth model based on the assumptions of a negative exponential decline of root length density (RLD) with soil depth, of a fixed ratio of RLD at the top of the soil profile and at rooting depth (rRLD) and of a fixed fraction of dry matter increase allocated to fine-roots (ffR) was formulated and used to describe the temporal and spatial variation of RLD found in the field. Slightly different estimates of ffR and of rRLD could be found for the different soil types, indicating a higher fraction of fine-root dry matter for the loess loam soil and a somewhat deeper root system for the humic loamy sand soil. A cross validation using the parameter values obtained from adjusting to the rooting data of one soil type for predicting RLD values of the other soil type, however, indicated that still quite satisfactory estimates (r2=0.91 and 0.95) of RLD could be obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004866823128
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  • 11
    Electronic Resource
    Electronic Resource
    Nitrate uptake by bean (Phaseolus vulgaris L.) roots under phosphate deficiency (2000)
    Springer
    Plant and soil 226 (2000), S. 79-85 
    Details
    ISSN: 1573-5036
    Keywords: nitrate reductase ; Phaseolus vulgaris ; phosphate deficiency ; plasma membrane ATPase ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Bean (Phaseolus vulgaris L.) plants were cultured for 19 d on complete or on phosphate deficient culture media. Low inorganic phosphate concentration in the roots decreased ATP level and nitrate uptake rate. The mechanisms which may control nitrate uptake rate during phosphate deficiency were examined. Plasma membrane enriched fractions from phosphate sufficient and phosphate deficient plants were isolated and compared. The decrease in total phospholipid content was observed in plasma membranes from phosphate deficient roots, but phospholipid composition was similar. No changes in ATPase and proton pumping activities measured in isolated plasma membrane of phosphate sufficient and phosphate deficient bean roots were noted. The electron microscope observations carried out on cortical meristematic cells of the roots showed that active ATPases were found in plasma membrane of both phosphate sufficient and phosphate deficient plants. The decrease in inorganic phosphate concentration in roots led to increased nitrate accumulation in roots, accompanied by a corresponding alterations in NO3 distribution between shoots and roots. Nitrate reductase activity in roots of phosphate deficient plants estimated in vivo and in vitro was reduced to 50–60% of the control. The increased NO3 concentration in root tissue may be explained by decreased NR activity and lower transport of nitrate from roots to shoots. Therefore, the reduction of nitrate uptake during phosphate starvation is mainly a consequence of nitrate accumulation in the roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026463307043
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  • 12
    Electronic Resource
    Electronic Resource
    Effect of alkaline and saline substrates on ABA contents, distribution and transport in plant roots (2000)
    Springer
    Plant and soil 225 (2000), S. 83-94 
    Details
    ISSN: 1573-5036
    Keywords: abscisic acid ; alkalinity ; exodermis ; rhizosphere ; roots ; soil ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The distribution of the phytohormone abscisic acid (ABA) between plant and soil and within plants growing on an alkaline substrate has been studied in order to separate the true effect of high soil pH from any effects that might be a result of the high salinity normally observed in alkaline soils. Leaves of a range of plants grown in an alkaline and saline solid substrate (municipal solid waste incinerator bottom slag) exhibited higher ABA levels than leaves of control plants. In contrast, roots of most plants grown on alkaline and saline substrates, particularly those without an exodermis (various species of Fabaceae), had slightly lower than or comparable ABA contents to control roots. However, in corn roots (Zea maysL. cv. Garant FAO 240) which possess a well-developed exodermis, alkaline and saline conditions in the rhizosphere did not reduce the endogenous ABA concentration, because the leaching of ABA from corn roots into the rhizosphere was lower than that from Vicia faba (variety Dreifache Weisse) roots. ABA efflux from corn and Vicia roots into the soil solution was observed only during the first days of the experiments and thereafter became substantially decreased. Because the leaching of ABA from Vicia faba roots into the rhizosphere was higher than that from corn roots, the leaves of Vicia plants grown in alkaline soil at low salinity no longer exhibited an elevated ABA concentration. However, whilst the roots of corn plants grown on desalted slag retained ABA levels that were higher than those of the control, the ABA content of leaves was not significant higher than the controls. For this reason, root ABA retention must be enough to induce tolerance to alkalinity in corn plants and there is no need to implicate changes in ABA concentrations in the aerial parts of the plant as having a role in this tolerance. In alkaline soil substrates, considerable portions of the ABA synthesised in the roots leached out into the soil solution of the rhizosphere according to the anion trap concept. An exodermis substantially reduces this leakage. The transient nature of ABA efflux into the rhizosphere was a result of the fact that the salt stress itself was only a transient phenomenon due to a washout of salt by irrigation. The results match predictions of mathematical models describing the effect of alkaline pH on the distribution of abscisic acid within plants and between roots and the rhizosphere. Species that can retain root ABA in the face of its tendency to leach into the more alkaline compartment are able to tolerate these normally harmful sites.
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    URL: http://dx.doi.org/10.1023/A:1026539311358
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  • 13
    Electronic Resource
    Electronic Resource
    Traits associated with improved P-uptake efficiency in CIMMYT's semidwarf spring bread wheat grown on an acid Andisol in Mexico (2000)
    Springer
    Plant and soil 221 (2000), S. 189-204 
    Details
    ISSN: 1573-5036
    Keywords: Andisol ; phosphatases ; phosphorus ; roots ; VA mycorrhiza ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphorus deficiency is a major yield limiting constraint in wheat cultivation on acid soils. The plant factors that influence P uptake efficiency (PUPE) are mainly associated with root characteristics. This study was conducted to analyze the genotypic differences and relationships between PUPE, root length density (RLD), colonization by vesicular arbuscular and arbuscular mycorrhizal (V)AM fungi and root excretion of phosphatases in a P-deficient Andisol in the Central Mexican Highlands. Forty-two semidwarf spring-bread-wheat (Triticum aestivumL.) genotypes from CIMMYT were grown without (−P) and with P fertilization (+P), and subsequently in subsets of 30 and 22 genotypes in replicated field trials over 2 and 3 years, respectively. Acid phosphatase activity at the root surface (APASE) was analyzed in accompanying greenhouse experiments in nutrient solution. In this environment, PUPE contributed more than P utilization efficiency, in one experiment almost completely, to the variation of grain yield among genotypes. Late-flowering genotypes were higher yielding, because the postanthesis period of wheat was extended due to the cold weather at the end of the crop cycles, and postanthesis P uptake accounted for 40–45% of total P uptake. PUPE was positively correlated with the numbers of days to anthesis (at −P r=0.57 and at +P r=0.73). The RLD in the upper soil layer (0–20 cm) of the wheat germplasm tested ranged from 0.5 to 2.4 cm cm-3 at –P and 0.7 to 7.7 at +P. RLD was the most important root trait for improved P absorption, and it was positively genetically correlated with PUPE (at –P r=0.42 and at +P r=0.63) and the number of spikes m-2 (at –P r=0.58 and at +P r=0.36). RLD in the upper soil layer was more important with P fertilizer application. Without P fertilization, root proliferation in the deeper soil profile secured access to residual, native P in the deeper soil layer. (V)AM-colonisation and APASE were to a lesser degree correlated with PUPE. Among genoptypes, the level of (V)AM-colonisation ranged from 14 to 32% of the RLD in the upper soil layer, and APASE from 0.5 to 1.1 nmol s-1 plant-1 10-2.
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    URL: http://dx.doi.org/10.1023/A:1004727201568
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  • 14
    Electronic Resource
    Electronic Resource
    Plant and soil microbial responses to defoliation in temperate semi-natural grassland (2000)
    Springer
    Plant and soil 220 (2000), S. 271-277 
    Details
    ISSN: 1573-5036
    Keywords: defoliation ; grassland ; grazing ; microbial activity ; microbial biomass ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract There is much interest in understanding the nature of feedback mechanisms between plants and soil organisms in grazed ecosystems. In this study, we examine the effects of different intensities of defoliation on the growth of three dominant grass species, and observe how these plant responses relate to the biomass and activity of the microbial community in the root zone. Our data show that grassland plants with varying tolerances to grazing have markedly different growth responses to defoliation, and that these responses vary with the intensity of cutting. Defoliation of grasses which are tolerant to grazing, namely Festuca rubra and Cynosurus cristatus, leads to a reduction in root mass and an increase in the allocation of resources to shoots. In contrast, defoliation of a grass with low tolerance to grazing, Anthoxanthum odoratum, had little effect on root mass, but increased the relative allocation of resources below-ground. In all plant species, defoliation led to an increase in soil microbial biomass and C use efficiency in the root zone. This response was greatest in the root zone of A. odoratum and is likely to be related to changes in root exudation pattern following defoliation. The significance of these changes in relation to soil nutrient dynamics and plant nutrient uptake during regrowth require further exploration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004787710886
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  • 15
    Electronic Resource
    Electronic Resource
    Compared root system architectures in seedlings and in vitro plantlets of Hevea brasiliensis, in the initial years of growth in the field (2000)
    Springer
    Plant and soil 223 (2000), S. 75-88 
    Details
    ISSN: 1573-5036
    Keywords: field trial ; microcutting ; roots ; rubber tree ; somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In vitro culture of Hevea was undertaken to propagate selected clones on their own roots. The challenge was to overcome the failure of cuttings due to the poor conformity of regenerated root systems. Trees of several juvenile or mature genotypes were propagated either by in vitro microcutting, or by somatic embryogenesis, and planted in the field. Certain static and dynamic components of the root system were observed at different growth stages, from 0 to 3 years, and compared to those of seedlings of the same age used in the trial as a reference. A simple method was designed for measuring the vigour and balance of the root system. The in vitro plantlets had a well-developed taproot and lateral root system, with an architecture similar to that of plants obtained from seed. Moreover, clear differences occurred between selected clones for the relative vigour of the tap roots, lateral roots and trunk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004829930841
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    Electronic Resource
    Electronic Resource
    Long-term effects of elevated atmospheric CO2 on below-ground biomass and transformations to soil organic matter in grassland (2000)
    Springer
    Plant and soil 224 (2000), S. 85-97 
    Details
    ISSN: 1573-5036
    Keywords: carbon ; CO2 enrichment ; nitrogen ; particulate organic matter ; roots ; tallgrass prairie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We determined the effects of elevated [CO2] on the quantity and quality of below-ground biomass and several soil organic matter pools at the conclusion of an eight-year CO2 enrichment experiment on native tallgrass prairie. Plots in open-top chambers were exposed continuously to ambient and twice-ambient [CO2] from early April through late October of each year. Soil was sampled to a depth of 30 cm beneath and next to the crowns of C4 grasses in these plots and in unchambered plots. Elevated [CO2] increased the standing crops of rhizomes (87%), coarse roots (46%), and fibrous roots (40%) but had no effect on root litter (mostly fine root fragments and sloughed cortex material 〉500 μm). Soil C and N stocks also increased under elevated [CO2], with accumulations in the silt/clay fraction over twice that of particulate organic matter (POM; 〉53 μm). The mostly root-like, light POM (density ≤1.8 Mg m-3) appeared to turn over more rapidly, while the more amorphous and rendered heavy POM (density 〉1.8 Mg m-3) accumulated under elevated [CO2]. Overall, rhizome and root C:N ratios were not greatly affected by CO2 enrichment. However, elevated [CO2] increased the C:N ratios of root litter and POM in the surface 5 cm and induced a small but significant increase in the C:N ratio of the silt/clay fraction to a depth of 15 cm. Our data suggest that 8 years of CO2 enrichment may have affected elements of the N cycle (including mineralization, immobilization, and asymbiotic fixation) but that any changes in N dynamics were insufficient to prevent significant plant growth responses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004771805022
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