Journal
BIOLOGY AND FERTILITY OF SOILS
Volume 48, Issue 8, Pages 967-971Publisher
SPRINGER
DOI: 10.1007/s00374-012-0699-9
Keywords
N fixation; N-15 dilution; Paenibacillus; Thuja plicata; Inoculation
Categories
Funding
- NSERC
- Global Forest [GF-18-2000-68]
- Science Council of British Columbia
- Brinkman and Associates Reforestation
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Diazotrophic bacteria previously isolated from internal tissues of naturally regenerating lodgepole pine (Pinus contorta var. latifolia (Dougl.) Engelm.) seedlings were tested for their ability to fix N in association with western red cedar (Thuja plicata Donn.). Surface-sterilized cedar seed was sown in glass tubes containing an autoclaved sand/montmorillonite clay mixture that contained a N-free nutrient solution labeled with N-15 as 0.35 mM Ca((NO3)-N-15)(2) (5 % N-15 label). After sowing, seed was inoculated with one of three bacterial strains: Paenibacillus polymyxa P2b-2R, P. polymyxa P18b-2R, or Dyadobacter fermentans P19a-2R. At the end of the 27-week plant growth period, P2b-2R was the only strain detected in the cedar rhizosphere. No bacteria were found inside plant tissues. Cedar foliar N concentrations were significantly enhanced (26-33 %, P < 0.05) in response to inoculation with all three bacterial strains but N-15 dilution (23 %, P < 0.05) was observed only in seedlings treated with strain P2b-2R. This strain also reduced seedling dry weight (27 %, P < 0.05). We observed similar trends in a second experiment with slight modifications to the protocol, but the magnitude of foliar N-15 dilution was greater (56 %, P < 0.05). Based on our results, we conclude that cedar seedlings inoculated with strain P2b-2R derived 23 and 56 % of their foliar N from bacterial N fixation in two seedling growth experiments.
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