Measurement of Ionic Concentration Gradients in Soil Near Roots

Farr, Emily; Vaidyanathan, L. V.; Ney, Pascal

doi:10.1097/00010694-196905000-00012

Cited by 44 publications

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“…We also thought the rhizosphere environment might show measurable alterations in properties like soil pH 3 6 which, in turn, might affect the soil's phosphate eharacteristics v. We report here an analysis oi phosphate concentration gradients determined by the method of Farr et al 3 in a sandy soil after uptake by roots of onion plants for up to 18 days. The presence of plant roots did not seem to affect the soil's high power for buffering changes in phosphate concentration.…”

Section: Discussionmentioning

confidence: 88%

The supply of nutrient ions by diffusion to plant roots in soil

1972

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The concentration of exchangeable P (to pa2 over 10 weeks) in a sandy soil was lowered by 50 per cent at the surface of a plane of onion roots. The rate of P uptake was uniform for 18 days, and the zone of depletion spread regularly. The effective difIusion coefficient increased by a factor of 2 to 3 over the period. The diffusion coefficient was approximately twice as great at a distance from the root plane as it was near the root plane, where the concentration was lower.

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Section: Discussionmentioning

confidence: 88%

The supply of nutrient ions by diffusion to plant roots in soil

1972

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“…After aerobic storage at ~ 45% moisture content with occasional remixing for 4 months, tlie soil was packed into specially designed cells (3 × 2 × 1 cm internal; see F a r r el al. 3 for details) at a density of 0.9 g oven dry soil/cc. W a t e r was added to raise the moisture to 0.7 g water/g soil, and allowed to equilibrate for 2 days.…”

Section: Methodsmentioning

confidence: 99%

The supply of nutrient ions by diffusion to plant roots in soil

Farr

Vaidyanathan

1972

Plant Soil

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SUMMARYThe concentration gradients of pa2 labbelled phosphate were measured in a Coral Rag Clay soll, placed in contact with planes of onion and ryegrass roots for up to 12 days' growth. After contact with the roots the soil block, 3 × 2 • 1 cm was quick-frozen and sliced into sections 0.1 m m thick, on which the p3~ was directly determined. The concentration : distance relationship showed only a small depletion profile, because the soil had a high power for buffering changes in phosphate concentration. There was also an unexpectedly large seatter ( i 5% of mean) in the initial distribution of p3~ in the undepleted soll; detailed analyses was, therefore, not possible. However, a eonstant reduced concentration at the root: soll boundary was indicated in all cases, corresponding to uptake (by onion) increasing linearly with square root of time. Calculations gave an effeetive diffusion coefficient in the range 0.29-0.71 X 10 -8 cm~/sec for a 10% depletion of the initial phosphate content at the root surface. These findings agree with previous inferences t h a t suppIy of phosphate to plant roots in this soil could be accounted for b y a simple diffusion proeess in which only N 10% of the long-term isotopically exchangeable phosphate was depleted; there was no evidence t h a t the phosptlate diffusion characteristics of this soil were altered b y the presence of plant roots.

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“…Farr et al (1969) held onion roots between two moist soil blocks. Many of the processes involved in nutrient acquisition occur in the soil zone very close to the roots.…”

Section: Separation Of Rhizosphere From Bulk Soilmentioning

confidence: 99%

Root Methods

2000

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Measurement of Ionic Concentration Gradients in Soil Near Roots

Cited by 44 publications

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The supply of nutrient ions by diffusion to plant roots in soil

The supply of nutrient ions by diffusion to plant roots in soil

The supply of nutrient ions by diffusion to plant roots in soil

Root Methods

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