The rhizosphere soils

Modifiers Modification of the rhizosphere soil with (e.g., protons, reductants)... 

W. Cheng, Q. Zhang, D. C. Coleman, C. R. Carroll, and C. A. Hoffman, Is available carbon limiting microbial respiration in the rhizosphere Soil Biol. Biochem. 28 1283 (1996). 

D. A. Barber and J. M. Lynch, Microbial growth in the rhizosphere. Soil Biology and Biochemistry 9 305 (1977). 

W. Kolb and P. Martin. Influence of nitrogen on the number of Ni-fixing and total bacteria in the rhizosphere. Soil Biology and Biochemistry 20 221 (1988). 

Fresh organic matter plays a fundamental role in plant nutrition by supplying nutrients released through degradation processes however, humified organic substances also become a source of nutrients when subjected to mineralization processes. The main aspects of the cycle of organic matter at the rhizosphere soil are reported in Chap. 6. 

There are indications that the variety of C substrates in the rhizosphere soil is basically too wide to be significantly affected by changes in quality of plant residues from the previous crop. For example, legumes as preceding crop were shown to increase significantly microbial diversity in the bulk soil, as estimated by Biolog assay, whereas in the rhizosphere soil this effect of legumes could not be detected (145). 

Reciprocally, the growth on single C source significantly decreases the bacterial diversity. For example, in the rhizosphere soil of potato, a dramatic reduction in the number of ribotypes was found by temperature gradient gel electrophoresis (TGGE) after 48 h of incubation with single C source substrate in Biolog microplate wells (I46). 

Grayston, SJ., Wang, S., Campbell, C.D., Edwards, A.C. Selective influence of plant species on microbial diversity in the rhizosphere. Soil Biol Biochem 1998 30 369-378. 

The Connecticut Agricultural Experiment Station is a site of extensive experimentation on chiral chlordanes in soils and plants. An experimental plot there was sprayed with a known amount of technical chlordane in 1960, and was then covered with turf until 1998 [175]. Enrichment of (+)-c/i-chlordane and ( )-fra s -chlordane was observed [175], consistent with global trends [140]. Soils with more nonracemic m-chlordane also had more nonracemic tra i-chlordane [175], suggesting that both isomers were concurrently degraded. Crop plants planted in these soils (e.g. zucchini, cucumber, pumpkin, lettuce, spinach, pepper, tomato) depleted chlordane concentrations in the rhizosphere soils closest to the roots [176] with resulting enrichments in chlordanes in the roots [177]. This... 

Shen Y, Strom L, Jonsson jA, and Tyler G. Low-molecular organic acids in the rhizosphere soil solution of beech forest (Fagus sylvatica L.) cambisols determined by ion chromatography using supported hquid membrane enrichment technique. Soil Biol. Biochem. 1996 28 1163-1169. 

Biomolecules are present in soils, especially in the rhizosphere, because of root exudates and microbial metabolites (Lynch, 1990a,b Marschner, 1998). Furthermore, in view of the stability constants of these biomolecular ligands with metals (NIST, 2004), a substantial fraction of the soluble metal ions in soil solution may be complexed with a series of biomolecules commonly present in microbial metabolites and root exudates. The concentrations in the rhizosphere of such metals as Cu, Mn, Zn, and Co vary with the seasons and are related to the presence of complexing biomolecules (Nielson, 1976 Linehan et al., 1989). The pH of the rhizosphere soil is generally lower than that of the corresponding... 

CieSlifiski, G., van Rees, K. C. J., Szmigielska, A. M., Krishnamurti, G. S. R., and Huang, P. M. (1998). Low-molecular-weight organic acids in the rhizosphere soils of durum wheat and their effect on cadmium bioaccumulation. Plant Soil 203, 109-117. 

Gottlein, A., Heim, A., and Matzner, E. (1999). Mobilization of aluminum in the rhizosphere soil solution of growing tree roots in an acidic soil. Plant Soil 211, 41-49. Griffiths, R. P., Baham, J. E., and Caldwell, B. A. (1994). Soil solution chemistry of... 

In the escape of natural gas from gas lines and from distribution networks, it is also possible to observe different reactions to the presence of the gas in the rhizosphere. Soil pollution by natural gas results in changes in the vegetation cover, which can terminate by its complete destruction. Desiccation, nanism and sterility are prevalent changes of the characteristic colour of leaves and their deformations are also observed. Only few species are resistant to a long-term action of natural gas. 

Molybdenum indirectly stimulates microbial activity in the plant rhizosphere by promoting root exudation. Foliar application of Mo was found to increase the concentrations of free amino acids, reducing sugars (arabinose), and organic acids in the rhizosphere soil of a rice crop... 

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