Modeling Zero Sink Nutrient Uptake by Roots With Root Hairs From Soil: Comparison of Two Models

Geelhoed, Jeanine S.; Mous, S.L.J.; Findenegg, G.R.

doi:10.1097/00010694-199708000-00003

Cited by 10 publications

(14 citation statements)

References 15 publications

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“…In this specific case, this can be attributed to the very high buffer capacity of the beech forest soil. Geelhoed et al () obtained, as in our model, higher plant P uptake by increasing the buffer capacity.…”

Section: Discussionsupporting

confidence: 78%

Assessment of diffusive phosphate supply in soils by microdialysis

Demand

Schack‐Kirchner

Lang

2017

J. Plant Nutr. Soil Sci.

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Standard procedures to assess P availability in soils are based on batch experiments with various extractants. However, in most soils P nutrition is less limited by bulk stocks but by strong adsorption and transport limitation. The basic principle of root‐phosphate uptake is to strip phosphate locally from the solid phase by forming a radial depletion zone in the soil solution, optionally enhanced by release of mobilizing substances. Microdialysis (MD), a well‐established method in pharmacokinetics, is capable to mimic important characteristics of P root uptake. The sampling is by diffusional exchange through a semipermeable membrane covering the probes with their sub‐mm tubular structure. Additionally, the direct environment of the probe can be chemically modified by adding, e.g., carboxylates to the perfusate. This study is the first approach to test the applicability of MD in assessing plant available phosphate in soils and to develop a framework for its appropriate use.We used MD in stirred solutions to quantify the effect of pumping rate, concomitant ions, and pH value on phosphate recovery. Furthermore, we measured phosphate yield of top‐soil material from a beech forest, a non‐fertilized grassland, and from a fertilized corn field. Three perfusates have been used based on a 1 mM KNO3 solution: pure (1), with 0.1 mM citric acid (2), and with 1 mM citric acid (3). Additionally, a radial diffusion model has been parametrized for the stirred solutions and the beech forest soil.Results from the tests in stirred solutions were in good agreement with reported observations obtained for other ionic species. This shows the principal suitability of the experimental setup for phosphate tests. We observed a significant dependency of phosphate uptake into the MD probes on dialysate pumping rate and on ionic strength of the outside solution. In the soils, we observed uptake rates of the probes between 1.5 × 10−15 and 6.7 × 10−14 mol s−1 cm−1 in case of no citrate addition. Surprisingly, median uptake rates were mostly independent of the bulk soil stocks, but the P‐fertilized soil revealed a strong tailing towards higher values. This indicates the occurrence of hot P spots in soils. Citrate addition increased P yields only in the higher concentration but not in the forest soil. The order of magnitude of MD uptake rates from the soil samples matched root‐length related uptake rates from other studies. The micro‐radial citrate release in MD reflects the processes controlling phosphate mobilization in the rhizosphere better than measurements based on “flooding” of soil samples with citric acid in batch experiments. Important challenges in MD with phosphate are small volumes of dialysate with extremely low concentrations and a high variability of results due to soil heterogeneity and between‐probe variability. We conclude that MD is a promising tool to complement existing P‐analytical procedures, especially when spatial aspects or the release of mobilizing substances are in focus.

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Section: Discussionsupporting

confidence: 78%

Assessment of diffusive phosphate supply in soils by microdialysis

Demand

Schack‐Kirchner

Lang

2017

J. Plant Nutr. Soil Sci.

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“…Model 1 describes the root hair uptake with a sink term and in this sense it is similar to the model proposed by Bhat et al. (1976) and Geelhoed et al. (1997).…”

mentioning

confidence: 77%

“…In Model 1, a sink term for root hair uptake in the conservation equation results in phosphate depletion in the root hair zone. Such sink terms have been developed before for soil systems (de Willigen & van Noordwijk, 1994; Geelhoed et al. , 1997; Bhat et al.…”

Section: Discussionmentioning

confidence: 99%

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A dynamic model of nutrient uptake by root hairs

et al. 2009

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Summary• Root hairs are known to be important in the uptake of sparingly soluble nutrients by plants, but quantitative understanding of their role in this is weak. This limits, for example, the breeding of more nutrient-efficient crop genotypes.• We developed a mathematical model of nutrient transport and uptake in the root hair zone of single roots growing in soil or solution culture. Accounting for root hair geometry explicitly, we derived effective equations for the cumulative effect of root hair surfaces on uptake using the method of homogenization.• Analysis of the model shows that, depending on the morphological and physiological properties of the root hairs, one of three different effective models applies. They describe situations where: (1) a concentration gradient dynamically develops within the root hair zone; (2) the effect of root hair uptake is negligibly small; or (3) phosphate in the root hair zone is taken up instantaneously. Furthermore, we show that the influence of root hairs on rates of phosphate uptake is one order of magnitude greater in soil than solution culture.• The model provides a basis for quantifying the importance of root hair morphological and physiological properties in overall uptake, in order to design and interpret experiments in different circumstances.

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“…It competes with phosphate (P) for binding sites in soils, like the ones provided by goethite (Smith et al 2002). Goethite is the prevalent Fe-oxide in temperate soils (Schwertmann and Taylor 1989) and a strong sorbent for As V (Gao and Mucci 2001;Manning and Goldberg 1996) as well as for P (Geelhoed et al 1997;Manning and Goldberg 1996). A higher affinity of goethite surface for As V than for P was reported by Gao and Mucci (2001) and Violante and Pigna (2002), while similar affinities for P and As V were found by Hiemstra and van Riemsdijk (1996) and Goldberg (1996, 1997).…”

Section: Introductionmentioning

confidence: 82%

Modelling rhizosphere transport in the presence of goethite, including competitive uptake of phosphate and arsenate

2009

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A modelling approach was used to extend the knowledge about the processes that affect the availability of the nutrient P and the toxic agent As V in the rhizosphere in the presence of a strong sorbent. Based on compartment system experiments in which Zea mays was grown the following hypothesis were assumed: a) measured P concentration gradients can be explained by the mobilisation of P by the root exudate citrate, and b) measured As V concentration gradients can be explained by the simultaneous effect of the competitive sorption of As V and P and the competitive uptake of As V and P. First, the feasibility of the applied description of soil chemical processes was justified. Then competitive uptake was implemented in the computer code using two different mathematical approaches. Our model calculation provided support for hypothesis a) and suggested that hypothesis b) has to be extended. The results show that the competitive uptake of As V and P has an influence on As V concentrations in the rhizosphere, but including competitive uptake was not sufficient to predict observed As V concentration profiles. Recent results on plant As-metabolism like As III efflux and Si As III interaction probably have to be included in addition for simulation of measured As V concentration profiles.

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Modeling Zero Sink Nutrient Uptake by Roots With Root Hairs From Soil: Comparison of Two Models

Cited by 10 publications

References 15 publications

Assessment of diffusive phosphate supply in soils by microdialysis

Assessment of diffusive phosphate supply in soils by microdialysis

A dynamic model of nutrient uptake by root hairs

Modelling rhizosphere transport in the presence of goethite, including competitive uptake of phosphate and arsenate

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