Effects of nitrate,ammonium and pH on the growth of conifer seedlings and their production of nitrate reductase |
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Authors: | William L Bigg T W Daniel |
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Institution: | (1) College of Natural Resources, Utah State University, 84322 Logan, Utah, USA;(2) Present address: Department of Botany, University of Aberdeen, St. Machar Dr., AB9 2UD Aberdeen, UK |
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Abstract: | Summary Lodgepole pine (Pinus contorta Dougl.), Engelmann spruce (Picea engelmanni Parry), and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were grown in open-ended tube cultures of sand and perlite, irrigated with nitrate, ammonium, and
a 1∶1 mixture of ammonium and nitrate, combined factorially with pH values of 4.6, 5.3 and 6.0 giving a total of nine treatments.
Douglas-fir showed intolerance to ammonium which was especially marked in root weight. Lodgepole pine and Engelmann spruce
made poor growth with nitrate, but showed little difference between ammonium and mixed sources. Only Douglas-fir showed a
significant response to pH treatments with pH 5.3 plants being largest. Contamination of the sand with carbonate-bicarbonate,
apparently caused seedlings grown in ammonium solutions to be larger in sand than in perlite.
Douglas-fir grown in perlite cultures showed a growth response like the first experiment and nitrate reductase activity in
the order nitrate > nitrateammonium mixture > ammonium. Plastic bead cultures had poor growth response due to low retention
of water by the substrate, but the nitrate reductase assays produced results like the perlite cultures.
Lodgepole pine grown in water culture demonstrated the well known pH shift associated with different nitrogen forms, and when
assayed for nitrate reductase these seedlings had larger relative activities than Douglas-fir, but the order of activity remained
nitrate > mixed source > ammonium. |
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