Rhizosphere effect

A. D. Rovira, Plant root excretions in relation to the rhizosphere effect I. The nature of root exudates from oats and peas. Plant and Soil 7 178 (1956). 

We further debate the methodologies used and the need for a protocol— what such a protocol would look like—and speculate on other aspects peculiar to the rhizosphere how long the rhizosphere effect lasts and whether it is transient, whether the effect is plant- or species-specific, the consequences of distinguishing rhizosphere and nonrhizosphere, and the consequences of selecting organisms for C and N transformations. 

Polyvinyl chloride cylinders -1- nylon gauze -1- device for continuous water supply Soil slices at measurable distance from soil-root interface. High bulk density of soil sampled. Nutrient uptake through an induced root hairs surface. Study of rhizosphere effect over a time and distance gradient from the soil-root interface. 47, 67, 127-129... 

Jordahl et al. (1997) reported that hybrid poplar root exudates stimulated soil microbial activity involved in chemical degradation. A significant increase occurred in populations involved in the degradation of several chemicals, but only a minor increase occurred in populations that degrade atrazine. Rhizosphere effects on atrazine degradation are unclear and remain under investigation. 

CBA contaminant by the increase of the degradation capacity of rhizosphere, but had no effect on total heterotrophic populations or on plant growth variables, indicating that inoculating did not increase the rhizosphere effect, but instead the degradation capacity of rhizosphere microorganisms. 

Rovira and McDougall (1967) give an excellent summary of our knowledge of the kinds of microorganisms that inhabit the rhizosphere, effect of age of plant, and the influence exerted on the various metabolic activities that they bring about or affect. 

It is now well established that roots of plants exude a large number of organic (and also mineral) substances and that it is this constant food source that is primarily responsible for the rhizosphere effect (Borner, 1960). Quantitative data on amounts of the various substances that are excreted from the roots are almost nonexistent, but the magnitude of the proliferation of microorganisms immediately surroUhding the roots shows positively that the food supply furnished by the roots is substantial (Stille, 1959). 

The ectorhizosphere is of prime importance for the whole soil-plant-microorganism environment as depending on soil type, plant species and environmental stresses, plants can release from 10% to 40% of their total net C assimilation per year from their roots (Lynch and Whipps, 1990 Van Veen el al, 1991 Uren, 2000 Berlin et al, 2003) through respiration and rhizodeposition the latter is responsible for generating the rhizosphere effect (Lynch and Whipps, 1990). 

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