A theoretical study of the distribution of substances around roots resulting from simultaneous diffusion and mass flow

Nye, P. H.; Marriott, F. H. C.

doi:10.1007/bf01881971

Cited by 143 publications

(66 citation statements)

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“…To simplify, we have distinguished what we call the "classical models", which have been developed from 1960 onwards (e.g. [1,9,11,19,21]), and more recent approaches, which integrated the plant structure and function to a greater extent.…”

Section: The Stagingmentioning

confidence: 99%

An introduction on below-ground environment and resource acquisition, with special reference on trees. Simulation models should include plant structure and function

Pagès¹,

Doussan

Vercambre³

2000

Ann. For. Sci.

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-Resource acquisition within the soil is a complex process, which consists of several sub-processes involving both the soil and the plant. A brief analysis of the whole system is presented, first by focusing on the components of the system, and then on the successive events. This analysis stresses the diversity and specificity of the components involved, as well as their interactive roles, at several organisation levels, both in space and time. Therefore, a systemic approach using dynamic models is defended in order to gather available knowledge and gain new insight within the whole system. In comparison to many of the traditional modelling approaches, which tended to over-simplify the plant part of the system, some new and promising attempts are presented. These new models give a good illustration of what can be expected to be gained by associating structural and functional characteristics of the plant components. model / root system / soil -plant system / uptake Résumé -Introduction sur l'environnement souterrain et l'acquisition des ressources, avec références particulières aux arbres. Les modèles de simulation devraient inclure la structure et les fonctions de la plante. L'acquisition des ressources du sol est un processus complexe, que l'on peut subdiviser en plusieurs processus plus élémentaires faisant intervenir conjointement la plante et le sol. Nous faisons une brève analyse de ce système, en insistant d'abord sur ses composants, puis sur les événements successifs. Cette analyse révèle la diversité et la spécificité des composants impliqués, ainsi que leurs rôles interactifs, à plusieurs niveaux d'organisation dans le temps et dans l'espace. Aussi, nous défendons une approche systémique, utilisant la modélisation dynamique, pour synthétiser les connaissances disponibles, et obtenir ainsi un nouvel éclairage sur le système pris dans sa globalité. En comparaison avec les approches de modélisation traditionnelles, qui tendent à simplifier outrageusement la partie plante du système, nous pré-sentons quelque démarches nouvelles et prometteuses. Ces derniers modèles illustrent bien les progrès que l'on peut escompter en associant davantage les caractéristiques structurales et fonctionnelles des composants de la plante. absorption / modèle / système racinaire / système sol -plante Ann. For. Sci. 57 (2000) [513][514][515][516][517][518][519][520] 513

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Section: The Stagingmentioning

confidence: 99%

An introduction on below-ground environment and resource acquisition, with special reference on trees. Simulation models should include plant structure and function

Pagès¹,

Doussan

Vercambre³

2000

Ann. For. Sci.

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“…Knowledge of the relation between the rate of ion absorption by plant roots and the concentration of the ion external to the root is important for doing plant nutrition studies, for investigating ion absorption mechanisms, and for evaluating mechanisms supplying nutrients to roots growing in soil (6,10). Hence, a convenient procedure that mathematically describes the kinetics of ion absorption would be useful.…”

mentioning

confidence: 99%

A Method for Characterizing the Relation between Nutrient Concentration and Flux into Roots of Intact Plants

Claassen¹,

Barber²

1974

Plant Physiol.

284

183

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A method based on the rate of depletion of a nutrient from solution was developed to characterize nutrient flux of plant roots. Nutrient concentration of the solution was measured at a series of time intervals to describe the complete depletion curve. An integrated rate equation, based on a Michaelis-Menten model, was developed and fit to the data of the depletion curve using a least-square procedure. The A procedure was also developed to measure uptake rate at constant concentration by adding nutrients to the pot at a constant rate that matched net influx into the root. This method also provides a means of measuring diurnal fluctuations in net influx rates.Knowledge of the relation between the rate of ion absorption by plant roots and the concentration of the ion external to the root is important for doing plant nutrition studies, for investigating ion absorption mechanisms, and for evaluating mechanisms supplying nutrients to roots growing in soil (6, 10). Hence, a convenient procedure that mathematically describes the kinetics of ion absorption would be useful.Ion absorption rate as related to ion concentration in the external solution has usually been measured using short term absorption by excised roots of isotopically labeled ions from solution (4) and long term absorption by intact plants from solutions maintained approximately at constant concentration (1). In the first, only ions with a convenient isotope for labeling can be studied and in both, separate measurements of uptake rate must be made for each of a graded series of ion con- THEORYWhen roots are in a solution containing salts, ions may move both into and out of the root. The terms we use to describe this ion movement are: influx, movement of ions from the external solution into the root; I, the rate of influx per unit length of root; efflux, the movement of ions out of the root into the external solution; E, the rate of efflux per unit length of root, and In, the net rate of influx per unit root length which is equal to I -E. The values of I, E, and ln in this paper are in terms of root length; however, root surface area, or root weight could be used if desired.When plants are grown in a solution of a constant volume, v, the decrease in ion content of the solution measures the net amount of the respective ion absorbed. The amount of ion in the nutrient solution, Q, is given by equation 1 where c is the ion concentration in solution. Q = cv (1) A plot of Q versus time, t, gives a curve showing the depletion of the ion from solution resulting from plant absorption and is called the depletion curve. The net influx per pot at any point on this curve is given by -dQ/dt. The slope of the curve can be estimated by expressing Q as a function of t and calculating the derivative. A relation Q = f(t) can be obtained by fitting the data using a parabolic spline function (3) or a cubic spline function (13). Both functions consist of a number of segments called splines fixed by the experimenter which describe the relation by a series of parabolic ...

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“…The two models are similar in approach and share many assumptions with their predecessors (Nye and Spiers, 1964;Nye and Marriot, 1969;Claassen alld Barber, 1976;Cushman, 1979;Barber and Cushman, 1981 ). They simulatc uptake by the average absorbing root in the average soil;…”

Section: Modeling Nutrient Uptake As a Component Ofmentioning

confidence: 94%

Modeling Nutrient Uptake as a Component of Loblolly Pine Response to Environmental Stress

Kelly¹,

Yanai²

1998

Ecological Studies

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well as accurate, nutrient-uptake models must be combined with detailed whole plant carbon allocation models so that interactions between the two models can occur and the results can describe verifiable changes in key parameters. Model DescriptionsWe employed two nutrient-uptake models, the Barber-Cushman model (Barber, 1984) as modified for thc personal computer by Oates and Barber (1987) and a steady-state model (Yanai, 1994). The two models are similar in approach and share many assumptions with their predecessors (Nye and Spiers, 1964; Nye and Marriot, 1969; Claassen alld Barber, 1976;Cushman, 1979;Barber and Cushman, 1981 ). They simulatc uptake by the average absorbing root in the average soil;there is no consideration of the geometry of the root system or of differences in root properties with age or morphology. The root is esscntially a uniform, linear sink and the amount of soil surrounding the root is defined by the average distance to the next root. In both models, nutrients move toward thc root by both mass now (Ihc movemcnt of solution to the root to support the transpiration stream) and by diffusion along the concentration gradient created by active uptake at the root surface. Uptake at the root surface is described by Michaelis-Menten kinetics.Neither model considers mycorrhizal association, except as it affects the values of parameters in the model, nor root modification of the rhizosphere, except for nutrient depletion.Both modeling approaches have been extensively tested in a number of applications through comparison of model predictions to observed responses. Although.dus is not a fail-safe process, experience has shown that opportunities for error propagation through these modeling approaches lie more with the development of the data used to provide initial values than with the concepts or codes within the models. Consequently, a portion of the discussion in this chpater is devoted to an analysis of how bcst to dcvelop key initial values.The major difference bctween the modcls is that the Barber-Cushman modcl simulates uptake ofa growing root system over a period of time, but without timevarying input. The rate of root growth is one of the values input to the model; that is. it must be spccificd in advance. Similarly.tllere are no inputs of nutrients to tllc soil ~ystem during tIle durution of a model run except as defined by the ability of thc solid phase (C,,) to maintain solution-phase concentration (CJ through buffering. We applied this model with considerable success in a simulation of loblolly pine seedlings for one growing season (Kelly et al., 1992). However, the BarberCushman model as presently configured could not be effectively linked to a plant simulator because it does not accept time-varying input to root growth and soil conditions. We also wanted to allow such feedback as the effect of nutrient uptake on root growth and the effcct of litter quality on nutrient supply. Therefore, in alklition to using the Barr~r-Cu~hman model, we d~veloped a new model to allow a more dynamic ...

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A theoretical study of the distribution of substances around roots resulting from simultaneous diffusion and mass flow

Cited by 143 publications

References 8 publications

An introduction on below-ground environment and resource acquisition, with special reference on trees. Simulation models should include plant structure and function

An introduction on below-ground environment and resource acquisition, with special reference on trees. Simulation models should include plant structure and function

A Method for Characterizing the Relation between Nutrient Concentration and Flux into Roots of Intact Plants

Modeling Nutrient Uptake as a Component of Loblolly Pine Response to Environmental Stress

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