ICOM1 Abstract
session: 1 (physiology) or 4 (ecology)
CADE-MENUN, BARBARA & SHANNON BERCH. Department of Soil Science, The
University of British Columbia, 139-2357 Main Mall, Vancouver, BC V6T
1Z4. BC Ministry of Forests, Glyn Road Research Station, 1320 Glyn
Road, Victoria, BC V8W 3E7 Canada. - Can western red cedar trees use P
from organic sources?
In some BC forests, western red cedar grows well in soils containing P
mainly in organic form, and shows less response to P fertilization than
other conifers. It was hypothesized that VA mycorrhizae allow cedar to
mineralize organic P. In a year-long greenhouse study, 2-year-old cedar
trees in pots with Turface were fed every 9 days with one of 11 P
treatments (in Long Ashton solution): No P; high phytic acid; low
phytic acid (NOTE: for all treatments, high is 50 mg P/L; low is 10 mg
P/L); high ATP; low ATP; high glycerophosphate; low glycerophosphate;
high pyrophosphate; low pyrophosphate; high orthophosphate; low
orthophosphate. Ten mycorrhizal trees were used per treatment; in half,
colonization was reduced with the fungicide benomyl. Growth was good,
relative to the No P and orthophosphate controls, with the organic
compounds glycerophosphate and ATP and with the inorganic pyrophosphate,
especially at the higher rates. The trees grew very poorly with phytic
acid, which may hve complexed Ca, Zn and Cu from the nutrient solution,
inducing Ca deficiencies. The P source influenced the activities of
acid and alkaline phosphatase of roots, but had no significant effect on
phosphodiesterase or pyrophosphatase in the soil or the plant roots. It
was impossible to distinguish enzyme activity of the plants and
mycorrhizae from that of rhizosphere microorganisms. Colonization
improved foliar P content, but other mycorrhizal effects may have been
masked by N enrichment from the benomyl.