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1.
Soil strength and macropore volume limit root elongation rates in many UK agricultural soils 总被引:2,自引:0,他引:2
Valentine TA Hallett PD Binnie K Young MW Squire GR Hawes C Bengough AG 《Annals of botany》2012,110(2):259-270
Background and Aims
Simple indicators of crop and cultivar performance across a range of soil types and management are needed for designing and testing sustainable cropping practices. This paper determined the extent to which soil chemical and physical properties, particularly soil strength and pore-size distribution influences root elongation in a wide range of agricultural top soils, using a seedling-based indicator.Methods
Intact soil cores were sampled from the topsoil of 59 agricultural fields in Scotland, representing a wide geographic spread, range of textures and management practices. Water release characteristics, dry bulk density and needle penetrometer resistance were measured on three cores from each field. Soil samples from the same locations were sieved, analysed for chemical characteristics, and packed to dry bulk density of 1·0 g cm−3 to minimize physical constraints. Root elongation rates were determined for barley seedlings planted in both intact field and packed soil cores at a water content close to field capacity (–20 kPa matric potential).Key Results
Root elongation in field soil was typically less than half of that in packed soils. Penetrometer resistance was typically between 1 and 3 MPa for field soils, indicating the soils were relatively hard, despite their moderately wet condition (compared with <0·2 MPa for packed soil). Root elongation was strongly linked to differences in physical rather than chemical properties. In field soil root elongation was related most closely to the volume of soil pores between 60 µm and 300 µm equivalent diameter, as estimated from water-release characteristics, accounting for 65·7 % of the variation in the elongation rates.Conclusions
Root elongation rate in the majority of field soils was slower than half of the unimpeded (packed) rate. Such major reductions in root elongation rates will decrease rooting volumes and limit crop growth in soils where nutrients and water are scarce. 相似文献2.
Penetrometer resistance,root penetration resistance and root elongation rate in two sandy loam soils
Root penetration resistance and elongation of maize seedling roots were measured directly in undisturbed cores of two sandy
loam soils. Root elongation rate was negatively correlated with root penetration resistance, and was reduced to about 50 to
60% of that of unimpeded controls by a resistance of between 0.26 and 0.47 MPa. Resistance to a 30° semiangle, 1 mm diameter
penetrometer was between about 4.5 and 7.5 times greater than the measured root penetration resistance. However, resistance
to a 5° semiangle, 1 mm diameter probe was approximately the same as the resistnace to root penetration after subtracting
the frictional component of resistance. The diameter of roots grown in the undisturbed cores was greater than that of roots
grown in loose soil, probably as a direct result of the larger mechanical impedance in the cores. 相似文献
3.
Root elongation, water stress, and mechanical impedance: a review of limiting stresses and beneficial root tip traits 总被引:12,自引:0,他引:12
Root elongation in drying soil is generally limited by a combination of mechanical impedance and water stress. Relationships between root elongation rate, water stress (matric potential), and mechanical impedance (penetration resistance) are reviewed, detailing the interactions between these closely related stresses. Root elongation is typically halved in repacked soils with penetrometer resistances >0.8-2?MPa, in the absence of water stress. Root elongation is halved by matric potentials drier than about -0.5?MPa in the absence of mechanical impedance. The likelihood of each stress limiting root elongation is discussed in relation to the soil strength characteristics of arable soils. A survey of 19 soils, with textures ranging from loamy sand to silty clay loam, found that ~10% of penetration resistances were >2?MPa at a matric potential of -10?kPa, rising to nearly 50% >2?MPa at - 200?kPa. This suggests that mechanical impedance is often a major limitation to root elongation in these soils even under moderately wet conditions, and is important to consider in breeding programmes for drought-resistant crops. Root tip traits that may improve root penetration are considered with respect to overcoming the external (soil) and internal (cell wall) pressures resisting elongation. The potential role of root hairs in mechanically anchoring root tips is considered theoretically, and is judged particularly relevant to roots growing in biopores or from a loose seed bed into a compacted layer of soil. 相似文献
4.
The effect of mechanical impedance on root growth in pea (Pisum sativum). II. Cell expansion and wall rheology during recovery 总被引:2,自引:0,他引:2
The aim of the present work was to determine the factors limiting growth in mechanically impeded roots. Pea roots were grown in compressed and uncompressed sand cores, and then removed and transferred to hydroponics. Root elongation was slowed in impeded sand cores and did not recover to the unimpeded rates until 60 h after transfer to the hydroponics system. Root diameter was greater in impeded roots, and only after 36 h in hydroponics was new root tissue produced of the same diameter as the unimpeded controls. The turgor pressure of the growing cells was measured with a turgor probe and was the same in both treatments. The slower elongation rate of the previously impeded roots was, therefore, the result of axial tightening of the cell walls. Cell length profiles suggested that axial cell wall tightening persisted in the unrestricted hydroponics system. Production of new cells in unrestricted conditions was required before root elongation returned to the unimpeded state. Osmotic potential was decreased by approximately 0.2 MPa in previously impeded roots compared with the unimpeded ones. This corresponds to a decrease in water potential of 0.2 MPa. These data are discussed in relation to regulation of cell extension, solute unloading and the penetration of compacted soils by roots. 相似文献
5.
F. Pax C. Blamey J. Bernhard Wehr Peng Wang Neal W. Menzies Peter M. Kopittke 《Plant and Soil》2014,379(1-2):301-314
Background and aims
Close regulation of cellular Ca in roots is required in the face of marked changes in soil solution Ca over time and space. This study’s aims were to quantify and gain insights into the ways in which roots respond to changes in solution Ca.Methods
Root elongation rate (RER) of cowpea (Vigna unguiculata (L.) Walp.) seedlings was determined at 0.05 to 15 mM Ca for up to 24 h both without and with added K, Mg, or Na. Root tip concentrations of Ca, K, Mg, and Na were determined and binding of cations by root tips estimated by subsequent Cu sorption.Results
Transfer from higher to lower Ca solutions (and with added K at high Ca) resulted in RER?≥?2 mm h?1 within minutes. This was attributed to greater cell wall relaxation through lower Ca binding aided by a decrease to pH?≤?5.1 in solution. Transfer to higher Ca solutions, which remained at ~pH 5.6, led to an equally rapid decrease in RER to ~0.5 mm h?1, an effect ascribed to greater cell wall binding of Ca. Thereafter, a gradual increase in RER to ~1.8 mm h?1 occurred over 24 h, an effect likely due to reduced cell wall Ca binding as shown by decreasing Cu sorption at a rate of 0.027 mmol Cu kg?1 FM h?1 over 24 h.Conclusion
The kinetics of changes in RER and cations in root tips suggest that roots respond to changes in solution Ca through effects on cell wall relaxation of the rhizodermis and outer cortex in the elongation zone. 相似文献6.
Background and aims
The root reinforcement (RR) models commonly used in slope stability modelling can be simply explained as a single soil additional cohesion parameter estimated with simple analytical functions of root traits. We have simulated 3D direct shear tests using the standard implicit Finite Element Method (FEM) and the Discrete Element Method (DEM), aiming to (i) evaluate the RR models and (ii) compare the two numerical approaches.Methods
In homogeneous soil with low cohesion, 36 straight, non-branched and thin root models were implanted in three parallel lines. Root traits, including orientation relative to the shear direction (45°, 90° and ?45°), longitudinal modulus of elasticity (10 MPa and 100 MPa), and bending and compressive behaviours (beam, truss and cable) were investigated.Results
Compared to the FEM, the DEM achieved consistent results and avoided convergence problems, but required longer computation time and used parameters potentially difficult to identify. Root reinforcement did not occur until significant plastic deformation of soil. The RR values estimated by the shear tests were much lower than those estimated by the usual RR models and were significantly dependent upon root traits.Conclusions
Ignoring the effect of root traits in RR models might lead to an important bias when using slope stability models. 相似文献7.
Background and aims
Root elongation is essential in the determination of the root system architecture (RSA). Using experimental data, we show how it varies in the RSA and suggest a new and simple modeling approach to predict these variations.Methods
We analyzed variation in elongation on data from pot-grown plants belonging to two different species (Helianthus annuus L. and Noccaea caerulescens (J.Presl & C.Presl) F.K.Mey). A stochastic model was designed with two successive steps to quantify and simulate these variations. The first step is the definition of a growth potential, reflected by the apical diameter, and depending on the size of the mother root. The second step, during elongation, describes the dynamic evolution of the meristem and its interaction with soil constraints.Results
The species exhibited differences in their structured variations and very large residual (pseudo-random) variability in elongation rate and final length. The two-step model allowed us to summarize these species characteristics, and to show the interest of considering the stochastic aspects of root growth to correctly simulate the RSA.Conclusions
Apart from being a more realistic way of simulating root development, this type of model raises new questions regarding the representation of root soil interactions during elongation. 相似文献8.
Root foraging capacity depends on root system architecture and ontogeny in seedlings of three Andean Chenopodium species 总被引:1,自引:0,他引:1
Ricardo Alvarez-Flores Thierry Winkel Anh Nguyen-Thi-Truc Richard Joffre 《Plant and Soil》2014,380(1-2):415-428
Aims
Morphological and ontogenetic variation in root system architecture holds ecological significance, particularly in low-resource habitats where soil rooting is critical for both seedling establishment and water and nutrient uptake. To assess this variation under contrasted agroecological backgrounds, root architecture and rooting patterns were compared in Andean populations of Chenopodium hircinum, Chenopodium pallidicaule and two ecotypes (wet- and dry-habitat) of Chenopodium quinoa.Methods
Seedlings were grown in rhizotrons under controlled water and nutrient availability. Root branching and elongation dynamics were characterized during 6 weeks after germination, while leaf area, above and below-ground biomass, and specific root length were determined at the end of the experiment.Results
Despite large differences in aboveground biomass, all populations showed similar herringbone root systems. The dry-habitat C. quinoa had generally the highest root trait values, with fast taproot elongation, thick roots and long root segments resulting in high total root length and deep root proliferation.Conclusion
Irrespective of their contrasting agroecological background, the studied chenopods displayed a similar root system topology. However, from very early development stages, they showed differential root foraging patterns with two extremes: fast and vigourous rooting at depth in the dry-habitat C. quinoa, and shallow and thin root system in C. pallidicaule adapted to shallow-soil and high-altitude habitats. 相似文献9.
QTL mapping and phenotypic variation for root architectural traits in maize (Zea mays L.) 总被引:1,自引:0,他引:1
Amy L. Burton James M. Johnson Jillian M. Foerster Candice N. Hirsch C. R. Buell Meredith T. Hanlon Shawn M. Kaeppler Kathleen M. Brown Jonathan P. Lynch 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2014,127(11):2293-2311
Key message
QTL were identified for root architectural traits in maize.Abstract
Root architectural traits, including the number, length, orientation, and branching of the principal root classes, influence plant function by determining the spatial and temporal domains of soil exploration. To characterize phenotypic patterns and their genetic control, three recombinant inbred populations of maize were grown for 28 days in solid media in a greenhouse and evaluated for 21 root architectural traits, including length, number, diameter, and branching of seminal, primary and nodal roots, dry weight of embryonic and nodal systems, and diameter of the nodal root system. Significant phenotypic variation was observed for all traits. Strong correlations were observed among traits in the same root class, particularly for the length of the main root axis and the length of lateral roots. In a principal component analysis, relationships among traits differed slightly for the three families, though vectors grouped together for traits within a given root class, indicating opportunities for more efficient phenotyping. Allometric analysis showed that trajectories of growth for specific traits differ in the three populations. In total, 15 quantitative trait loci (QTL) were identified. QTL are reported for length in multiple root classes, diameter and number of seminal roots, and dry weight of the embryonic and nodal root systems. Phenotypic variation explained by individual QTL ranged from 0.44 % (number of seminal roots, NyH population) to 13.5 % (shoot dry weight, OhW population). Identification of QTL for root architectural traits may be useful for developing genotypes that are better suited to specific soil environments. 相似文献10.
Alireza Nakhforoosh Heinrich Grausgruber Hans-Peter Kaul Gernot Bodner 《Plant and Soil》2014,380(1-2):211-229
Background and Aims
Under limited moisture conditions, roots can play an outstanding role with respect to yield stability by effective absorption of water from soil. A targeted integration of root traits into plant breeding programs requires knowledge on the existing root diversity and access to easy and cost-effective methods. This study aimed to assess wheat root diversity, root properties in relation to water regime, and the efficiency of root capacitance for in situ screening.Methods
Root morphological, anatomical properties and root capacitance of wheat species from different ploidy levels were studied under field conditions in 2 years contrasting in water regime. Soil water content was weekly measured.Results
Significant genotypic differences were observed for most root traits. The investigated genotypes exploited different strategies to maximize soil water depletion, e.g. high topsoil root length density, low tissue mass density, high specific root length, deep rooting and looser xylem vessels. Multivariate statistics of root traits revealed an acceptable genotypic differentiation according to regional origin, genetics and capacity to extract soil water.Conclusions
Under supply-driven environments, dehydration avoidance via water uptake maximization can be achieved through high topsoil rooting density. In this regard, root capacitance can be useful for in situ screening. 相似文献11.
Background and Aims
Root system development is affected by soil conditions. The effects of bulk density, water content and penetration resistance on root development processes were investigated in peach trees.Methods
Peach tree rootstocks were grown in various soil conditions, combining two bulk densities (1.2 and 1.5?g soil.cm-3) and three water contents (0.14, 0.17 and 0.20?g.g-1soil). Root parameters (tip diameter, length of apical unbranched zone, branching density and diameters of main and lateral roots) and plant growth (leaves, branches, trunk, root dry mass) were measured. Root growth processes (elongation, branching) were studied using relationships between root parameters.Results
The proportion of biomass allocated to each plant compartment was similar whatever the soil conditions. Variations in root development were best explained by the variation in penetration resistance, rather than other soil properties. Increased soil penetration resistance reduced the root elongation rate, especially for thick roots. In addition, the branching pattern was affected. In soil with a high penetration resistance, the root system shape differs from a typical herringbone pattern.Conclusions
These results allow quantification of the root system plasticity, and improve our understanding of the interactions between root development and soil properties. 相似文献12.
Rebecca E. Haling Matthew K. Tighe Richard J. Flavel Iain M. Young 《Plant and Soil》2013,368(1-2):619-627
Background and aims
Much of our understanding of plant root decomposition and related carbon cycling come from mass loss rates calculated from roots buried in litter bags. However, this may not reflect what actually happens in the soil, where the interactions between root and soil structure presents a more complex physico-chemical environment compared to organic matter isolated in a porous bag buried in disturbed soil. This work investigates the potential of using X-ray micro-computed tomography (CT) to measure root decomposition in situ.Methods
Roots of Vicia faba L. were excised from freshly germinated seeds, buried in re-packed soil cores and cores incubated for 60 days. Changes in root volume and surface area were measured using repeated scans. Additional samples were destructively harvested and roots weighed to correlate root mass with root volume. The method was further applied to an experiment to investigate the effects of soil bulk density and soil moisture on root decomposition.Results
Root volume (X-ray CT) and root mass (destructive harvest) decreased by 90 % over the 60 day incubation period, by which stage, root volume and mass had stabilised. There was a strong correlation (R 2?=?0.97) between root volume and root mass.Conclusions
X-ray CT visualization and analysis provides a unique toolbox to understand root decomposition in situ. 相似文献13.
María Benlloch-Gonzalez Jens Berger Helen Bramley Greg Rebetzke Jairo A. Palta 《Plant and Soil》2014,374(1-2):963-976
Background and Aims
Understanding crop responses to increasing atmospheric CO2 requires knowledge of how their root systems grow, proliferate and function. The effect of elevated CO2 on the growth and proliferation of wheat root system (Triticum aestivum L.), was examined.Methods
Two pairs of sister lines of wheat contrasting in vigour (CV97 and CV207) and tillering (7750N and 7750PF) were grown in rhizo-boxes under ambient (380 μl L?1) and elevated CO2 (700 μl L?1), and the root growth and proliferation mapped.Results
Elevated CO2 effects on shoot and root biomass were observed in the lines contrasting for vigour, but not in the lines contrasting for tillering. Root biomass was reduced by 67 % in the high vigour line CV97, reducing total plant biomass by 26 % compared to the low vigour line, CV207. This was due to a reduction in root length down the 1 m soil profile and root proliferation in the top 0.2 m layer. The reduction in root biomass was not compensated by an increase in shoot biomass.Conclusions
The reduction in root biomass under elevated CO2 in the vigour line CV97 can be explained through its inability to increase the sink strength due to the failure to increase tiller number to which the plant presumably responded by increasing losses of the newly assimilated carbon by respiration. 相似文献14.
Satoshi Ogawa Michael Gomez Selvaraj Angela Joseph Fernando Mathias Lorieux Manabu Ishitani Susan McCouch Juan David Arbelaez 《Plant and Soil》2014,375(1-2):303-315
Aims
In rice, seminal root elongation plays an important role in acquisition of nutrients such as N and P, but the extent to which different N forms and P concentrations affect root growth is poorly understood. This study aimed to examine N- and P-mediated seminal root elongation response and to identify putative QTLs associated with seminal root elongation.Methods
Seminal root elongation was evaluated in 15 diverse wild and cultivated accessions of rice, along with 48 chromosome segment substitution lines (CSSLs) derived from a cross between the rice variety ‘Curinga’ and Oryza rufipogon (IRGC 105491). Root elongation in response to different forms of N (NH4 +, NO3 ? and NH4NO3) and concentrations of P was evaluated under hydroponic conditions, and associated putative QTL regions were identified.Results
The CSSL parents had contrasting root responses to N and P. Root elongation in O. rufipogon was insensitive to N source and concentration, whereas Curinga was responsive. In contrast to N, seminal root elongation and P concentration was positively correlated. Three putative QTLs for seminal root elongation in response to N were detected on chromosome 1, and one QTL on chromosome 3 was associated with low P concentration.Conclusions
Genetic variation in seminal root elongation and plasticity of nutrient response may be appropriate targets for marker-assisted selection to improve rice nutrient acquisition efficiency. 相似文献15.
Ying Long Chen Vanessa M. Dunbabin Art J. Diggle Kadambot H. M. Siddique Zed Rengel 《Plant and Soil》2012,354(1-2):141-155
Background and aims
Intra-specific variation in root system architecture and consequent efficiency of resource capture by major crops has received recent attention. The aim of this study was to assess variability in a number of root traits among wild genotypes of narrow-leafed lupin (Lupinus angustifolius L.), to provide a basis for modelling of root structure.Methods
A subset of 111 genotypes of L. angustifolius was selected from a large germplasm pool based on similarity matrices calculated using Diversity Array Technology markers. Plants were grown for 6?weeks in the established semi-hydroponic phenotyping systems to measure the fine-scale features of the root systems.Results
Root morphology of wild L. angustifolius was primarily dominated by the taproot and first-order branches, with the presence of densely or sparsely distributed second-order branches in the late growth stage. Large variation in most root traits was identified among the tested genotypes. Total root length, branch length and branch number in the entire root system and in the upper roots were the most varied traits (coefficient of variation CV >0.50). Over 94% of the root system architectural variation determined from the principal components analysis was captured by six components (eigenvalue >1). Five relatively homogeneous groups of genotypes with distinguished patterns of root architecture were separated by k-means clustering analysis.Conclusions
Variability in the fine-scale features of root systems such as branching behaviour and taproot growth rates provides a basis for modelling root system structure, which is a promising path for selecting desirable root traits in breeding and domestication of wild and exotic resources of L. angustifolius for stressful or poor soil environments. 相似文献16.
Chantal Planchamp Dirk Balmer Andreas Hund Brigitte Mauch-Mani 《Plant and Soil》2013,367(1-2):605-614
Background and aims
The root surface of a plant usually exceeds the leaf area and is constantly exposed to a variety of soil-borne microorganisms. Root pathogens and pests, as well as belowground interactions with beneficial microbes, can significantly influence a plants' performance. Unfortunately, the analysis of these interactions is often limited because of the arduous task of accessing roots growing in soil. Here, we present a soil-free root observation system (SF-ROBS) designed to grow maize (Zea mays) plants and to study root interactions with either beneficial or pathogenic microbes.Methods
The SF-ROBS consists of pouches lined with wet filter paper supplying nutrient solution.Results
The aspect of maize grown in the SF-ROBS was similar to soil-grown maize; the plant growth was similar for the shoot but different for the roots (biomass and length increased in the SF-ROBS). SF-ROBS-grown roots were successfully inoculated with the hemi-biotrophic maize fungal pathogen Colletotrichum graminicola and the beneficial rhizobacteria Pseudomonas putida KT2440. Thus, the SF-ROBS is a system suitable to study two major belowground phenomena, namely root fungal defense reactions and interactions of roots with beneficial soil-borne bacteria.Conclusions
This system contributes to a better understanding of belowground plant microbe interactions in maize and most likely also in other crops. 相似文献17.
Aims
Plant tolerance to herbivory has often been linked to plant growth rate, with faster growing plants that present high tissue turnover rates expected to be more tolerant than slower-growing plants. We tested whether this relationship also holds for rootstock growth rate and tolerance to apple replant disease (ARD).Methods
An ARD susceptible rootstock, M.26 and ARD tolerant rootstock, CG.6210 were grown in soil from an apple replant site (FS) and in pasteurized soil (PS) from the same site. Total below ground biomass production was determined by harvesting a subset of plants per soil treatment and rootstock at 11, 17, and 23 weeks after planting. Root samples were collected prior to each harvesting date to determine root respiration and total carbon (C) and nitrogen (N) content. Root dynamics were tracked during the growing season by digitally photographing root observation windows.Results
Total root biomass, first and second order roots, and second-to-first order root ratio were higher in CG.6210 than in M.26 in both soil treatments. Roots of CG.6210 were thinner and had lower N concentration than those of M.26. Roots of M.26 had longer lifespans than those of CG.6210, and the mortality risk of M.26 roots was 56 % that of CG.6210 roots.Conclusion
Our study indicates that rootstocks with faster growing root systems can tolerate ARD infection by investing fewer resources in individual root construction that can be shed more readily. 相似文献18.
Changes in root size and distribution in relation to nitrogen accumulation during maize breeding in China 总被引:3,自引:0,他引:3
Xiaochao Chen Jie Zhang Yanling Chen Qian Li Fanjun Chen Lixing Yuan Guohua Mi 《Plant and Soil》2014,374(1-2):121-130
Background and aims
Modern maize breeding has increased maize yields worldwide. The changes in above-ground traits accompanying yield improvement are well-known, but less information is available as to the effect of modern plant breeding on changes in maize root traits.Methods
Root growth, nitrogen uptake, dry matter accumulation and yield formation of six maize hybrids released from 1973 to 2000 in China were compared. Experiments were conducted under low and high nitrogen supply in a black soil in Northeast China in 2010 and 2011.Results
While nitrogen accumulation, dry matter production and yield formation have been increased, modern maize breeding in China since 1990 has reduced root length density in the topsoil without much effect on root growth in the deeper soil. The efficiency of roots in acquiring N has increased so as to match the requirement of N accumulation for plant growth and yield formation. The responses of root growth, nitrogen and dry matter accumulation, and grain yield to low-N stress were similar in the more modern hybrids as in the older ones.Conclusions
Modern maize breeding has constitutively changed root and shoot growth and plant productivity without producing any specific enhancement in root responsiveness to soil N availability. 相似文献19.
A. Carminati D. Vetterlein N. Koebernick S. Blaser U. Weller H.-J. Vogel 《Plant and Soil》2013,367(1-2):651-661
Aims
Roots need to be in good contact with the soil to take up water and nutrients. However, when the soil dries and roots shrink, air-filled gaps form at the root-soil interface. Do gaps actually limit the root water uptake, or do they form after water flow in soil is already limiting?Methods
Four white lupins were grown in cylinders of 20 cm height and 8 cm diameter. The dynamics of root and soil structure were recorded using X-ray CT at regular intervals during one drying/wetting cycle. Tensiometers were inserted at 5 and 18 cm depth to measure soil matric potential. Transpiration rate was monitored by continuously weighing the columns and gas exchange measurements.Results
Transpiration started to decrease at soil matric potential ψ between ?5 kPa and ?10 kPa. Air-filled gaps appeared along tap roots between ψ?=??10 kPa and ψ?=??20 kPa. As ψ decreased below ?40 kPa, roots further shrank and gaps expanded to 0.1 to 0.35 mm. Gaps around lateral roots were smaller, but a higher resolution is required to estimate their size.Conclusions
Gaps formed after the transpiration rate decreased. We conclude that gaps are not the cause but a consequence of reduced water availability for lupins. 相似文献20.
Henri de Parseval Sébastien Barot Jacques Gignoux Jean-Christophe Lata Xavier Raynaud 《Plant and Soil》2017,412(1-2):97-114