Soil plants

Instiximental neutron activation analysis (INAA) is considered the most informative and highly sensitive. Being applied, it allows detecting and determination of 30-40 elements with the sensitivity of 10 -10 g/g in one sample. The evident advantage of INAA is the ability to analyze samples of different nature (filters, soils, plants, biological tests, etc.) without any complex schemes of preliminai y prepai ation. 

Figure 12 Interactions of soil emissions of NO with O3 in plant canopies and NO, uptake by vegetation in determining the net exchange of NO between soil-plant and the atmosphere.

Fig. 7. Main contributions to the water balance in soil-plant system...

Coarse Mechanically produced From soil, plants, sea salt, volcanoes, wind blown material, abrasion... 

Zhang, J. Davies, W.J. (1989). Abscisic acid produced in dehydrating roots may enable the plant to measure the water status of the soil. Plant, Cell and Environment, 12, 73-81. 

El Zorgani GA, Omer IS, Abdullah AM. 1986. Bound residues of endosulfan and carbofuran in soil and plant material. Proceedings of the Final Research Co-ordination Meeting on Isotopic Tracer-aided Studies of Unextractable or Bound Pesticide Residues in Soil, Plants, and Food. Vienna, Austria International Atomic Energy Agency, 51-56. 

R. Kuchenbuch and A. Jungk, A method for determining concentration profiles at the soil-root interface by thin slicing rhizospheric soil. Plant Soil 68 391 (1982). R. Schonwitz and H. Ziegler, Quantitative and qualitative aspects of a developing rhizosphere microflora of hydroponically grown maize seedlings. Z Pflanzenernahr. Bodenk. 749 623 (1986). 

M. J. Goss, Consequences of the activity of roots on soil. Plant Root Growth an Ecological Perspective (D. Atkinson, ed.), Blackwell, Oxford, 1991, p. 171. 

Phosphorus (P) is one of the major limiting factors for plant growth in many soils. Plant availability of inorganic phosphorus (Pi) can be limited by formation of sparingly soluble Ca phosphates, particularly in alkaline and calcareous soils by adsorption to Fe- and Al-oxide surfaces in acid soils and by formation of Fe/ Al-P complexes with humic acids (94). Phosphorus deficiency can significantly alter the composition of root exudates in a way that is, at least in some plant species, related to an increased ability for mobilization of sparingly soluble P sources (29,31,71). 

D. Vetterlein and H. Marschner, U.se of a niicrotensiometer technique to study hydraulic lift in sandy soil planted with pearl millet (Penni.setiiin americanum L. Leeke). Plant Soil 149 215 (1995). 

It has been found that many environmental factors influence the amount and composition of root exudates and hence the activity of rhizosphere microbial populations. Microbial composition and species richness at the soil-plant interface are related either directly or indirectly to root exudates and thus vary according to the same environmental factors that influence exudation. In es.sence, the rhizosphere can be regarded as the interaction between soil, plants and microorganisms. Figure 2 shows some of the factors associated with these interactions, which will be discussed during the course of the chapter. Here we mention briefly the influence of some plant and microbial factors on root exudation and rhizosphere microbial populations, while soil factors are discussed later. 

X. L. Li. E. George, and H. Marschner, Extension of the phosphorus depletion zone in VA-mycorrhizal white clover in calcareous. soil. Plant and Soil I3I 4 (1991). X. L. Li, E. George, and H. Marschner, Acquisition of phosphorus and copper by VA-mycorrhizal hyphac and root-to-shoot transport in white clover. Plant and Soil 135 49 (1991). 

Table 4 Soil Sampling Procedures, Limitations, and Advantages of Some Experimental Soil-Plant Systems Adopted for Studying Rhizosphere Processes... 

Understanding of the soil-plant-microbe relationship probably remains one of the most difficult challenge for life sciences due to the integration of observations at many scales. New efforts relying more on holistic approaches are needed. 

P. H. Nye and P. B. Tinker, Solute Movement in the Soil-Plant Sy.stem, Blackwell, Oxford, 1977. 

B. Jensen, Distribution of C in pulse-labelled spring barley effect of light intensity and length of photoperiod before labelling. Acta Agric. Scand. Sect. B Soil Plant Sci. 44 214 (1994). 

J. Swinnen, Evaluation of the use of a model rhizodeposition technique to separate root and microbial respiration in. soil. Plant Soil /65 89 (1996). 

F. Asmar, T. S. Gahoonia, and N. E. Nielsen, Barley genotypes differ in activity of soluble extracellular phosphatase and depletion of organic phosphorus in the rhizo.sphere soil. Plant Soil 172 1 (1995). 

R. Kuchenbuch and A. Jungk, A inethod for determining concentration profiles at the soil-root interface by thin slicing rhizospheric soil. Plant Soil 68 39 (1982). 

G. Matschonat and R. Vogt, Equilibrium solution composition and exchange properties of disturbed and undisturbed soil samples from an acid fore.st soil. Plant Soil I83 l (1996). 

S. Mpepereki, A. G. Wollum II, and F. Makonese, Diversity in symbiotic specificity of cowpea rhizobia indigenous to Zimbabwean soils. Plant Soil 186 167-171 (1996). 

N. Claas.sen, K. M. Syring, and A. Jungk, Verification of a mathematical model by. simulating potassium uptake from soil. Plant Soil. 95 209 (1986). 

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