Abstract
A mathematical model has been developed which is capable of simulating the population dynamics of microbial biomass surrounding a root which is releasing soluble and insoluble carbon compounds into the soil. The model simulates the interconversions of C between different pools within the soil as well as the diffusion and mass flow of soluble carbon. Two main aspects of carbon release were examined: (i) a strategy where exudate was released uniformly over the root surface was compared to the case where exudation was confined to a small region behind the root tip; (ii) the situation in which all the C released was in soluble form was compared to the case of an approximately equal partition between soluble and insoluble forms. Substantial differences between the different simulations were found. It was shown that the maximum concentration and penetration of soluble exudates differed markedly between different simulations and the implications of this for micronutrient acquisition by phytosiderophores and for colonisation of the rhizosphere by root pathogens were discussed. The different simulations also predicted very different biomass distributions in the rhizosphere in both space and time.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Anderson, T and Domsch, K H 1985 Maintenance carbon requirements of actively-metabolizing microbial populations under in situ conditions. Soil Biol. Biochem. 17, 197–203.
Barber, S A 1984 Soil Nutrient Bioavailability: A Mechanistic Approach. Wiley, New York.
Chapman, S J and Gray, T R G 1981 Endogenous metabolism and macromolecular composition of Arthrobacter globiformis. Soil Biol. Biochem. 13 11–18.
Chapman, S J and Gray, T R G 1986 Importance of cryptic growth, yield factors and maintenance energy in models of microbial growth in soil. Soil Biol. Biochem. 18, 1–4.
Coody, P N, Sommer, L E and Nelson, D W 1986 Kinetics of glucose uptake by soil microorganisms. Soil Biol. Biochem. 18, 283–289.
Curl, E A and Truelove, B 1986 The Rhizoshpere. Springer-Verlag, New York.
Griggin, G J, Hale, M G and Shay, F J 1976 Nature and quantity of sloughed organic matter produced by roots of axenic peanut plants. Soil Biol. Biochem. 8, 29–32.
Hiltner, L 1904 U neuere Erfahrungen und Probleme auf dem Gebiet der Bodenbakteriologie und unter besonderer Berücksichtigung der Gründüngung und Brache. Arb. Dtsch. Landwirt. Ges. 98, 59–78.
Jenkinson, D S and Ladd, J N 1981 Microbial biomass in soil: measurement and turnover. In Soil Biochemistry Vol. 5. Eds. E APaul and J NLadd. pp 415–471. Dekker, New York.
Lambers, H 1987 Growth, respiration, exudation and symbiotic associations: The fate of carbon translocated to the roots. In Root Development and Function. Eds. P JGregory, J VLake and D ARose. Soc. Exp. Biol. Seminar Series 30. Cambridge University Press, Cambridge, UK.
Marschner, H, Römheld, V and Kakmak, I 1987 Root-induced changes of nutrient availability in the rhizosphere. J. Plant Nutr. 10, 1175–1184.
McCully, M E and Canny, M J 1985 Localization of translocated 14C in roots and root exudates of field grown maize. Physiol. Plant. 65, 380–392.
McDougall, B M and Rovira, A D 1970 Sites of exudation of 14C-labelled compounds from wheat roots. New Phytol. 69, 999–1003.
Newman, E I 1985 The rhizosphere: Carbon sources and microbial populations. In Ecological Internations in Soil. Ed. A HFitter. pp 107–122. Blackwell Scientific Publications, London.
Newman, E I and Watson, A 1977 Microbial abundance in the rhizosphere: A computer model. Plant and Soil 48, 17–56.
Nye, P H and Marriott, F H C 1969 A theoretical study of the distribution of substances around roots resulting from simultaneous diffusion and mass flow. Plant and Soil 30, 459–472.
Pirt, S J 1975 Principles of Microbe and Cell Cultivation. Blackwell, Oxford.
Rovira, A D 1965 Plant root exudates and their influence upon soil microorganisms. In Ecology of Soil-Borne Plant Pathogens. Eds. K FBaker and W CSnyder. pp 170–186. University of California Press, Berkeley.
Smith, G D 1978 Numerical Solution of Partial Differential Equations: Finite Difference Methods. Oxford Applied Mathematics and Computing Science Series. Oxford University Press, Oxford, UK.
Smith, J L, McNeal, B L and Cheng, H H 1985 Estimation of the soil microbial biomass: An analysis of the respiratory response of soils. Soil Biol. Biochem. 17, 11–16.
Smith, J L, McNeal, B L, Cheng, H H and Campbell, G S 1986 Calculation of microbial maintenance rates and net nitrogen mineralization in soil at steady state. Soil Sci. Soc. Am. J. 50, 332–338.
Smith, O L 1982 Soil Microbiology: A Model of Decomposition and Nutrient Cycling. CRC Press, Inc., Boca Raton, FL.
Tousson, T A, Bega, R V and Nelson, P E (Eds) 1970 Root Diseases and Soil-Borne Pathogens. University of California Press, Berkeley.
Trofymow, J A, Coleman, D C and Cambardella, C 1987 Rates of rhizodeposition and ammonium depletion in the rhizosphere of axenic oat roots. Plant and Soil 97, 333–334.
Van derWerf, H and Verstraete, W 1987a Estimation of active soil microbial biomass by mathematical analysis of respiration curves: Development and verification of the model. Soil Biol. Biochem. 19, 253–260.
Van derWerf, H and Verstraete, W 1987b Estimation of active soil microbial biomass by mathematical analysis of respiration curves: Calibration of the test procedure. Soil Biol. Biochem. 19, 261–266.
Whipps, J M 1984 Environmental factors affecting the loss of carbon from the roots of wheat and barley seedlings. J. Exp. Bot. 35, 767–773.
Whipps, J M and Lynch, J M 1983 Substrate flow and utilization in the rhizosphere of cereals. New Phytol. 95, 605–623.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Darrah, P.R. Models of the rhizosphere. Plant Soil 133, 187–199 (1991). https://doi.org/10.1007/BF00009191
Received:
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF00009191