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This article in SSSAJ

  1. Vol. 38 No. 4, p. 668-672
    Received: Oct 10, 1973
    Accepted: Mar 11, 1974

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Nitrate Production in Two Forest Soils and Nitrate Reduction in Pine1

  1. W. F. Theobald and
  2. W. H. Smith2



Acid forest soils showed low capacities for nitrification even when substrate NH4-N was increased. Under forest soil pH conditions and NO3 levels typical of the lower coastal plain, pine roots (Pinus spp.) possessed low nitrate reductase (NR) activities.

An in vivo assay showed NR activity in slash pine roots (P. elliottii Englm. var. ‘elliottii’). Activity depended on NO3 level and pH of nutrient solution. Highest activity was with 100 ppm NO3-N at pH 6. Ammonium-grown seedlings possessed low levels of activity even at pH 4, indicating constitutive nature or early induction of the enzymes. Radicles of seeds aseptically germinated actively reduced NO3, indicating activity within the root tissues. Daily patterns of fluctuation in NR activity similar to the pattern for photosynhesis were observed. In vitro assay attempts were unsuccessful, due apparently to the presence of inhibitors.

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