N-15 foliar dilution of western red cedar in response to seed inoculation with diazotrophic Paenibacillus polymyxa

作者：Bal Amandeep; Chanway Christopher P^*

来源：Biology and Fertility of Soils, 2012, 48(8): 967-971.

DOI：10.1007/s00374-012-0699-9

• N fixation
• N-15 dilution
• Paenibacillus
• Thuja plicata
• Inoculation

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.

• 出版日期2012-11