Root activity

P. Bottner, Z. Sallih, and G. Billes, Root activity and carbon metabolism in soils. Biol. Fertil. Soils 7 71 (1988). 

More recently, it was realized that rhizosphere cartton dynamics are more complex than these early models envisaged. Jones and Darrah (51-53) showed lhal roots actively scavenge their root exudates and that the re-uptake of exudates was selective. In most situations, sugars and amino acids were. scavenged by roots, while organic acid exudates were not (54). The authors also found that exudation losses were largely passive. This active involvement of the root essen-... 

Chrysoma pauciflosculosa Michx. (Asteraceae) u.s. Root Active... 

P. Horn, L. Holzl, W. Todt, D. Matthies, Isotope abundance ratios of Sr in wine provenance determination, in a tree-root activity study, and of Pb in a pollution study on tree-rings, Isotopes Environ. Health Studies, 34 (1998), 31-42. 

The longitudinal fluxes that may arise from the preferential flow paths of water and solutes along large root channels are even less well documented than the radial fluxes of trace elements in the rhizosphere. It is well known that roots tend to colonize former biopores, as indicated in Section 4.2. As many of those macropores, especially vertical/subvertical biopores created by earthworms or root activity, are prone to preferential flow during re-saturation events, they may complicate our understanding of (1) the directions of trace elements and water fluxes, and ultimately, (2) the origin of the solutes circulating in the root environment. This process has received virtually no attention so far, however, possibly because of the practical difficulties associated with its quantitative assessment. 

Several chemical extractants has been developed over the years from the concept of simulating plant root activity and with the purpose to obtain an appropriate measure of the readily soluble inorganic forms to represent the plant available soil P. Out of the several extractants, depending upon soil pH, presence of iron and aluminum compoimds or calcium carbonate one particular method is selected for analysis. The most common methods along with extractant composition, soikextractant ratio and shaking time are furnished below ... 

Cell cultures are ideal axenic physiological systems to study herbicide action without problems of cuticular transfer or complications of translocation. Still, not all metabolic systems function in all cells at all times in the cell cycle. Inhibitors of photosynthesis are often inactive in non green cells, and root-active herbicides may be degraded in green cells. Nutritional components in the medium may interfere with herbicide action. 

Younts and York Jr. (1956), similarly, failed to demonstrate any pronounced effect of deep placement of lime and fertilizer upon plant growth or upon root activity. Com yields were unaffected by the deep placement but crimson clover yields were increased somewhat. 

Despite their critical role in biogeochemical cycles in terrestrial ecosystems, the relationships between root activity, mineral weathering and the bioavailability of metals are largely unknown. Hence, a study was designed to establish the impact of root activity on mineral weathering, and to determine its consequences for the spatial distribution of trace metal forms in the vicinity of roots. 

As a by-product, the weathering processes occurring in the rhizosphere have produced yellowish-coloured amorphous Ee-oxyhydroxides that revealed the thickness of the soil affected by root activity, where chemical, mineralogical and biological properties were changed with respect to the bulk. 

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