Roots uptake from soil

TCDD was applied to the soil and root uptake from soil was then measured in oats and soybeans (Kearney et al. 1971). Oat and soybean plants (at all growth stages) accumulated very small quantities of... 

Gplant-us = concentration in plant tissue resulting from root uptake from soil (mg/kg or pGi/kg) Gplant-da = concentration in edible parts of plant as a result of direct deposition of airborne contaminants (mg/kg or pGi/kg)... 

J. S. Gcelhoed. L. J. M. Sipko, and G. R. Findernegg, Modelling zero sink nutrient uptake by roots with root hairs from. soil compari.son of two models. Soil Sci. 162 544 (1997). 

Uptake of 14C-labeled OCDD was studied in a closed, aerated-soil plant system for 7 days after application of the OCDD to soil (Schroll et al. 1994). The BCF (concentration of 14C equivalent to the OCDD in plant dry matter divided by 14C-labeled OCDD in dry soil) was 0.742 in carrot root and 0.085 in carrot shoots grown on OCDD-contaminated soil as compared to a BCF of not determinable and 0.084 in the control carrot root and shoots, respectively. There was no transport of 14C-labeled OCDD between the roots and shoots or vice versa. The residues in roots were due only to root uptake from the soil those in shoots were due only to foliar uptake from the air. 

Lead is considered to be a non-essential metal to plants, and only a small proportion of the lead in soils is biovailable to plants (Alloway, 1990). Visible symptoms of toxicity, though unspecific to Pb, are smaller leaves and a stunted growth. Leaves may become chlorotic and reddish with necrosis and the roots may turn black. Several plant species, ecotypes and bacterial strains have been known to develop Pb tolerance. The phytotoxicity of Pb is low as it has very limited availability and uptake from soil and soil solutions. However, plant roots are usually able to take up and accumulate large quantities of Pb2+ in soil and culture solutions but translocation to aerial shoots is generally limited due to binding at root surfaces and cell walls (Lagerwerff, 1971 Jones et al., 1973 Lane and Martin, 1977). 

The uptake if iron often requires Fe(II) as the bioavailable form, and uptake from soils containing insoluble Fe(III) is accomplished by phenolic compounds which are exuded by certain plants (Chaney and Bell, 1987). A particular use of staining has been in the study of the sites if iron reduction in plants, using Prussian blue stain (PB) (Ambler et al., 1971 Brown and Ambler, 1974). The method consists of placing the roots in a nutrient solution containing Fe(III) and ferricyanide. Since PB can be produced both from Fe(III) and Fe(CN)64 and from Fe(II) and Fe(CN)63, reduction of either source of iron in the presence of the roots will produce PB at the sites of... 

There are two possible sources of PCDD/Fs to vegetation the atmosphere and soil. Initially it was thought that PCDD/Fs would not be present in the atmosphere in quantities sufficient to contaminate plants owing to their low volatility, and early research in this area focused on uptake from soil. There are three possible pathways of soil-bound PCDD/Fs to aerial plant parts root uptake and translocation, volatilization followed by adsorption to foliage, and transfer of soil particles (see Figure 1). The first of these pathways has received the most attention. 

In Table 5 the observed transfer factors (TF) for roots, stems and grains are listed for the two agricultural systems. The TF is calculated as the ratio of the massic activity in plant material to its massic activity in soil. Generally a lower TF for root samples from the conventional system was observed indicating lesser uptake from soil to root of the radionuclides in this study. 

The limited information on the plant uptake of other actinide elements (U, Np, Am, Cm) indicates that higher CR values can be expected relative to those observed for Pu. Values for Am based on uptake by roots and from deposition on foliage approach or exceed the 10-1 value used in the LMFBR assessment thus, the value used in dose assessments is probably realistic but not conservative. Price (32) reported CR values of 10-1 to 10-2 for 237Np assimilated by the root pathway. Based on these data and on the low K. for Np (Table II), it appears that this element exhibits a higher mobility than the other actinides. A potential CR > 10-1 due to uptake from soil and from direct contamination of foliage is hypothesized for Np. Curium-244 uptake by the root pathway yielded CR values of 10 3 to 10-1, according to pot culture experiments (32, 52). 

Sulfur and Molybdenum, Phosphorus and Molybdenum The availability of soil Mo or fertilizer Mo to plants will vary significantly with the presence of competing ions, such as P04 and S04. Stout et al. (1951) found that adding S04 depressed Mo uptake, possibly because S04 and Mo04 compete for the same absorption sites on roots. Singh, Mehta, and Singh (1986) observed that Mo concentrations in plants decreased with S application, but increased with P application (Table 15.10). Addition of phosphate fertilizer perhaps can stimulate Mo uptake from soil solution. 

Gahoonia, T.S. and Nielsen, N.E. (1997) Variation in root hairs of barley cultivars doubled phosphorus uptake from soil. Euphytica 98, 177-1 82. 

Geelhoed, J.S., Mous, S.L.J., Findenegg, G.R., 1997. Modehng zero sink nutrient uptake by roots with root hairs from soil comparison of two models. Sod Sci. 162, 544—553. 

Soil extractions under the best of circumstances provide information on net or residual available phenolic acids but there is no reliable way, at present, to determine when or where these compounds function as active inhibitors, and Many inhibitory effects of phenolic acids are rapidly reversed once phenolic acids are eliminated (e.g., leaching, microbial activity, root uptake) from the root environment. Sustained inhibition requires that phenolic acids at the right concentration and physicochemical state, and under the right environmental conditions be continuously present and in contact with a large fraction of the root system. Unfortunately available/active phenolic acids in soils are dynamic, ever changing. Realistic data on flows into and out of various phenolic acid pools in the soil are notoriously difficult to get by soil extractions, since each extraction represents a point in time and, if for example, input equals output, then net flow between two extraction times will appear to be zero. In fact, considerable flows may be occurring between sources and sinks within the soil that are just not detectable by way of soil extractions. 

Polyvinyl chloride cylinders -1- nylon gauze -1- device for continuous water supply Soil slices at measurable distance from soil-root interface. High bulk density of soil sampled. Nutrient uptake through an induced root hairs surface. Study of rhizosphere effect over a time and distance gradient from the soil-root interface. 47, 67, 127-129... 

D. E. Crowley. V. Romheld, H. Marschner, and P. J. Szaniszlo. Root-microbial effects on plant iron uptake from siderophores and phytosiderophores. Plant Soil 142 1 (1992). 

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