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Soil Science Society of America Journal Abstract -

A Kinetic Analysis of Phosphate Absorption by Excised Roots of Millet, Barley, and Alfalfa1


This article in SSSAJ

  1. Vol. 24 No. 1, p. 33-35
    Received: July 30, 1959
    Accepted: Aug 11, 1959

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  1. J. C. Noggle and
  2. Maurice Fried2



A kinetic analysis was made of P absorption at steady state by excised roots of millet, barley, and alfalfa. Short-time absorption studies indicated that the rate of P absorption is greater for millet than barley and greater for barley than alfalfa. The specific reaction rate constants for the metabolic turnover of the two carriers of P are of the same order of magnitude for the three plant species. They are approximately 1 × 10-2 moles of P per mole of combined carrier per second. The apparent dissociation constant for carrier “a” is approximately 9 × 10-4 for all three plant species, but the value for carrier “b” varies from 3 × 10-6 for millet and alfalfa to 8 × 10-6 for barley. The major difference between species is in concentration of carrier. These values are 2 × 10-7, 3 × 10-8, and 1 × 10-8 moles per g. of millet, barley, and alfalfa roots, respectively.

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