A technique incorporating several improvements over previous approaches was used to measure responses of plants to several patterns of phosphorus (P) distribution throughout the root zone. Nutrient solutions were moved in and out of three discrete root zones separated by Permagum barriers. Movement was accomplished by an automatic elevating platform which periodically raised solution reservoirs from a resting position to a height sufficient for flushing each compartment with nutrient solution.Root weight increases were observed in those regions where P was present in the root zone. The lower the zone of P supply, the more diminished was the response. These findings were interpreted in terms of sugar translocation and immobilization within the roots. The P and potassium contents of the roots were unaffected by P distribution patterns but calcium and magnesium contents were markedly increased in older tissues where P was present in the ambient solution. These data supported the concept that internally translocated P and externally absorbed P have apparently differing effects at a given root site because the former does not reach the site in the same quantity as the latter. P uptake data suggested that ions absorbed at one point on a root may depress the absorption at a lower point. No significant treatment effects on shoot growth or cation and N contents of shoots were observed. The P content of the shoots, however, was in proportion to the amount of root surface in contact with ambient P.

No abstract

A mixture of microorganisms cultured under nonsterile conditions on propham (isopropyl carbanilate) herbicide as the sole carbon source was tested for its ability to degrade a number of chlorinated and nonchlorinated anilide compounds. In separate tests under pure-culture conditions, species of the microbial mixture reacted individually in a manner similar to the nonsterile whole. The microorganisms grew and respired rapidly on nonchlorinated anilides, but ring chlorination depressed respiration and inhibited growth. Studies on the dimethylphenylureas indicated that the two methyl groups were primarily responsible for the biological stability of these compounds. All other anilides were degraded by hydrolysis of the side chain followed by metabolic degradation of the ring. Appearance of aniline in the medium depended on the relative rates of production by side chain hydrolysis and disappearance by ring degradation. Acylanilides were hydrolyzed more rapidly than carbanilates and chlorinated rings were degraded much more slowly than unchlorinated rings. Chlorination affected rates of ring degradation and microbial respiration in the following order (most rapid to least rapid): 0 > 2,4 > 2,4,5 > 3 > 4 ≥ 3,4. It is proposed that this unexpected degradative sequence might be explained in terms of the degree of microbial toxicity in the system generated by the formation of chloroazobenzenes from chloroaniline intermediates.

No abstract

A mixed suspension of microorganisms containing at least 7 tentatively identified genera was derived from a liquid mixture of soil and IPC. This suspension, when applied to nonsterile greenhouse soil flats, markedly reduced or eliminated the toxicity of the phenylcarbamates IPC, CIPC, and Swep to several test plant species. The suspension of microorganisms was effective in the soil for between 2 and 3 months. These findings have implications for the degradation of chemicals resistent to the native soil population.