Carbonate translocation

E. Liljeroth, P. Kuiknian, and J. A. Van Veen, Carbon translocation to the rhizo-sphere of maize and wheat and influence on the turnover of native soil organic-matter at different soil nitrogen levels. Plant Soil 161 233 (1994). 

H. Lambers. Growth, respiration, exudation and symbiotic as.stx iations the fate of carbon translocated to the roots. Root Development and Function (P. J. Gregory, J. V. Lake, and D. A. Rose, eds.), Cambridge University Pre.ss, London, 1987, p. 125. 

Erland, S. E., Finlay, R. D. Soderstrom, B. (1991). The influence of substrate pH on carbon translocation in ectomycorrhizal and non-mycorrhizal pine seedlings. New Phytologist, 119, 235-42. 

Jacobs, H., Boswell, G. P., Ritz, K., Davidson, F. A. Gadd, G. M. (2002). Solubilization of calcium phosphate as a consequence of carbon translocation by Rhizoctonia solani. FEMS Microbiology Ecology, 40, 65—71. 

Wells, J. M., Boddy, L. Evans, R. (1995). Carbon translocation in mycelial cord systems of Phanerochaete velutina (DC. Pers.) Parmasto. New Phytologist, 129, 467-76. 

Korshin et al. reported an outstanding double stereoselective alkenyla-tion through a 1,5 sulfur-to-carbon translocation on a proline-derived scaffold [169]. 5-Exo-trig cyclization of the radical derived from 181 led to bi-cyclic adduct 182, which collapsed to the open thiyl radical (Scheme 59). The sole stereocontrol exerted by the cyclization step allows for the resulting vinyl translocation to occur entirely stereoselectively. Since the reaction was carried out in the presence of a styryltin derivative, consecutive intermolecular vinylation occurred, leading to bisvinyl compoimd 183 in very high yield (86%). The styrylsulfonyl moiety could be converted to a formyl group. 

Sucrose has several important roles in plants. First, sucrose accounts for a large portion of the CO, absorbed during photosynthesis. Second, most of the carbon translocated throughout plants is in the form of sucrose. Finally, sucrose is an important energy storage form in many plants. 

Other than a nutritional role linked to mineralization processes, humic compounds have been hypothesized to directly affect plant nutrition, since it has been suggested that roots may take up low-molecular-weight humic molecules (21). Interestingly, plants have been ob.served to express carriers for amino acids (22) and small peptides (23) at the root level. Certain components of the humic fraction have been found inside root cells and were, moreover, translocated to the shoots (24,25). Recent experiments performed on rice cells in suspension culture seem to suggest that they may use carbon skeletons from humic molecules to synthesize proteins and DNA (26). 

Deng, X. et al. (2007) Translocation and fate of multi-walled carbon nanotubes in vivo. Carbon, 45 (7), 1419-1424. 

Van den Bossche, J. et al. (2010) Efficient receptor-independent intracellular translocation of aptamers mediated by conjugation to carbon nanotubes. Chemical Communications, 7379-7381. Mu, Q.X., Broughton, D.L. and Yan, B. 

Endosomal leakage and nuclear translocation of multiwalled carbon nanotubes developing a model for celluptake. Nano Letters, 9 (12), 4370-4375. 

Another prominent feature of arid/semi-arid soils is the translocation of carbonates. Invariably, carbonates, mainly calcite, are present throughout all the profile. Commonly, however, there is a distinct horizon of accumulation, frequently in the form of concretions. More than one and up to three such horizons of accumulation can be found in some soils. It appears that clay translocation from the upper into lower horizons does take place, though to a limited extent, in arid soils. Soils with B2 horizons are not rare. 

Atrazine enters plants primarily by way of the roots and secondarily by way of the foliage, passively translocated in the xylem with the transpiration stream, and accumulates in the apical meristems and leaves (Hull 1967 Forney 1980 Reed 1982 Wolf and Jackson 1982). The main phytotoxic effect is the inhibition of photosynthesis by blocking the electron transport during Hill reaction of photosystem II. This blockage leads to inhibitory effects on the synthesis of carbohydrate, a reduction in the carbon pool, and a buildup of carbon dioxide within the leaf, which subsequently causes closure of the stomates, thus inhibiting transpiration (Stevenson et al. 1982 Jachetta et al. 1986 Shabana 1987). 

A very attractive feature of radical chemistry is the generation of a novel radical after cyclization or any other radical translocation. This feature allows the inclusion of a second carbon—carbon bond-forming event and can, in principle, be extended even further. The resulting tandem reactions [38] can be extremely useful for the construction of complex molecules. Impressive early results have been reported by Stork in applications directed towards the synthesis of prostaglandins [39]. Our catalytic conditions also allow the realization of tandem reactions. An example including a mechanistic proposal is shown in Scheme 12.20. 

Although these reservoirs may be highly contaminated with PCDD/PCDFs, the chemical and physical properties of these compounds imply that dioxins and furans will stay adsorbed to organic carbon in soils or other particles. On the other hand, mobilization can occur in the presence of lipophilic solvents (leaching into deeper layers of soils and/or groundwater) or in cases of erosion or run-off from topsoil (translocation into the neighbourhood). Experience has shown that transport of PCDD/PCDFs due to soil erosion and run-off does not play a major role in environmental contamination and human exposure (Fiedler 1995, 1999). 

A mechanistic scheme involving weakly bridged intermediates, liable to undergo carbon-carbon bond rotation and counteranion translocation, analogous to that proposed for chlorination (see above), has been reported also for the bromination of dienes in order to rationalize the product stereochemistry. 

Pantarotto D, Briand JP, Prato M, Bianco A (2004a) Translocation of bioactive peptides across cell membranes by carbon nanotubes. Chem. Commun. 16-17. 

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