Elements in Plants

Plant micronutrients are those required in plant tissue at concentrations which are equal to or less than 100 mg kg-1 dry weight. Macronutrients or major elements are those which are needed in concentrations of 1000 mg kg-1 or more in dry weight of the plant. Typical concentrations of elements in plants are given by Bowen (1966), Kabata-Pendias and Pendias (1984) and Markert (1992) Angelone and Bini (1992) have detailed elemental concentrations for plants and soils of western Europe. 

It has been pointed out by a number of workers (for example Jarrell and Beverley, 1981) that the terms used to designate the quantities of an element in plant tissues can be ambiguous. Content has been used both for concentration and for total mass , ie. the concentration x the biomass. These authors further point out that decreasing concentrations could result from increased biomass, with the total taken up remaining constant, or even increasing the dilution effect . 

If the supply of an element is inadequate, the growth of the plant is abnormal or stunted and its further development, especially its metabolic cycles, are disordered. Although deficiency symptoms are difficult to generalise, they may be quite characteristic for a particular element. Kabata-Pendias and Pendias (1984) and 

Hewitt and Smith (1975) have listed descriptions of deficiency symptoms, the most frequent being chlorosis. Visible symptoms are important in diagnosis of deficiencies however, disturbance of metabolic processes and consequent losses in production of biomass may occur before the deficiency symptoms are recognised. 

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Calcium. Soil minerals are a main source of calcium for plants, thus nutrient deficiency of this element in plants is rare. Calcium, in the form of pulverized limestone [1317-65-3] or dolomite [17069-72-6] frequendy is appHed to acidic soils to counteract the acidity and thus improve crop growth. Such liming incidentally ensures an adequate supply of available calcium for plant nutrition. Although pH correction is important for agriculture, and liming agents often are sold by fertilizer distributors, this function is not one of fertilizer manufacture. 

Zinc, like most metals, is found in all natural waters and soils as well as the atmosphere and is an important trace element in plant and animal life (see Mineral nutrients). Rocks of various kinds contain 20—200 ppm zinc and normal soils 10—30 ppm (average ca 50 ppm) in uncontaminated areas. The average zinc content of coal is 33 ppm. Seawater contains 1—27 )-lg/L (median ca 8 p.g/L), and uncontaminated freshwater usually <10 / g/L. 

The literature includes a number of mis-matches, the following standing as examples for the many The use of bovine liver and other animal tissues for QC in the analysis of hmnan body fluids should not be considered by analysts. The matrix and the levels of trace elements do not match the levels to be analyzed, which may lead to serious errors. An even more severe mis-use was recently reported by Schuhma-cher et al. (1996) for NIST SRM 1577a Bovine Liver, which was used for QC in the analysis of trace elements in plant materials and soil samples in the vicinity of a municipal waste incinerator. Also recently, Cheung and Wong (1997) described how the quality control for the analysis of trace elements in clams (shellfish) and sediments was performed with the same material NIST SRM 1646, Estuarine sediment. Whilst the selected SRM was appropriate for sediments, its usefulness as a QC tool for clams is difficult to prove see also Chapter 8. This inappropriate use is the more mystifying because a broad selection of suitable shellfish RMs from various producers is available. 

Table 7.1. Concentrations of selected trace elements in plants grown on noncontaminated arid and semi-arid soils3...

Shacklette, H.T., J.A. Erdman, T.F. Harms, and C.S.E. Papp. 1978. Trace elements in plant food stuffs. Pages 25-68 in F.W. Oehme (ed.) Toxicity of Heavy Metals in the Environment. Part I. Marcel Dekker, New York. 

Jones and Isaac 16 ) compared atomic absorption spectroscopy and spark emission spectroscopy for the determination of several elements in plant tissue. By comparing results statistically using a t-test, no significant differences were found for calcium, manganese, iron, copper, zinc, and aluminium, but significant differences were found for potassium and magnesium at the 0.01 % level. Breck162) made a similar comparison study for 15 elements. 

In the control area, Lombador, the phosphorus, an essential element in plants nutrition, presents, in the relationsoil-plant, a different behavior from the other areas. This can be related to the substratum rock in the Lombador area which is composed of metassediments (turbidites) and are not included in Volcano Sedimentary Complex as the other areas where mining works have occurred. 

The distribution of elements between the solid and the liquid phase is of primary importance for the transport processes in the environment. In addition, the uptake of elements in plants and other living organisms is determined by the speciation of the element in that phase. 

Crasser, K.D. (1998) HMGl and HU proteins architectural elements in plant chromatin. Trends Plant Sci. 3, 260-265. 

The analysis of soils and plant material are common examples used to demonstrate ICP applications. Dahlquist and Knoll(43) compared the preparation and ICP analyses of botanicals (16 elements) and soils (11 elements) with few exceptions the ICP values for the CII botanicals were in excellent agreement with the assigned values, and the soil analyses were in excellent agreement with FAA analyses of soil digests. )ones( 4) reported the analysis of 17 elements in plant material and soils but confirmation of the two analyses was not given. Alder, et. aJ.(75) describe the unique analysis of ammonia-nitrogen in soils by gas evolution into an ICP no interferences were observed from the concomitants evaluated and acceptable recoveries were obtained. Irons et. al.(76) compared the ICP analyses of 13 elements in NBS orchard leaves and bovine liver to the data obtained by FAA and energy dispersive x-ray. 

Discussion 7.13. Determination of trace elements in plants and feeds... 

ARC] Agricultural Research Council (1963) Report of Group on Comparison of Methods of Analysis of Mineral Elements in Plants. Agricultural Research Council, London, 52 pp. 

Shkolnik MY (1984) Trace Elements in Plants, New York, Elsevier... 

Titanium in Plants and Animals. In 1896 C. E. Wait found large amounts of titanium in the ashes of bituminous and anthracite coals, oak wood, and apple and pear wood (23, 57). L. G. Willis, in his bibliography on the minor elements in plant and animal nutrition, gave several references to the presence of small amounts of titanium in soils, in plants, and in the human body (58). 

High biological activity within the soil promotes metabolism between soil and plants and is an essential part of sustainable plant production and fertiliser management. The role of soil organisms is central to soil processes and fertility since they render available the elements in plant residues and organic debris entering the soil (Alfoldi ef al. 2002). 

Arafat and Glooschenko [95] have described a method for the simultaneous determination of these elements in plants which does not involve the use of perchloric acid. 

Schramel et al. [103] and Wolnik et al. [104] and Hahn et al. [105] have investigated the applicability of this technique to the determination of elements in plant materials. 

Schramel [103] discusses the conditions for multi-element analysis of over 50 trace elements, giving detection limits. Wolnik [104] described a sample introduction system that extends the analytical capability of the inductively coupled argon plasma/polychromator to include the simultaneous determination of six elemental hydrides along with a variety of other elements in plant materials. Detection limits for arsenic, bismuth, selenium and tellurium range from 0.5 to 3 ng/ml and are better by at least an order of magnitude than those obtained with conventional pneumatic nebulisers, whereas detection limits for the other elements investigated remain the same. Results from the analysis of freeze-dried crop samples and NBS standard reference materials demonstrated the applicability of the technique. Results obtained by the analysis of a variety of plant materials are presented in Table 7.10. 

Reuter [111] has discussed in detail a technique for the measurement of trace elements in plant materials by X-ray fluorescence spectrometry. 

Critical concentrations of elements in plants have been defined by Beckett and Davis (1977) and Davis and Beckett (1978) as those concentrations which cause toxic reactions and reduce yield (biomass). They presented yield curves of plants grown in the presence of toxic metals ... 

Fergusson, J. E. (1990). Heavy Elements in Plants. Chemistry, Environmental Impact and Health Effects, London Pergamon Press. 

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