植物促生菌对桉树幼苗生长及其氮素来源的影响

Effect of Plant Growth-promoting Rhizobacteria (PGPR) on the Growth and Nitrogen Source of Eucalyptus Seedlings

利用^(15)N稳定性同位素示踪法,研究施氮水平对接种或不接种植物促生菌的桉树幼苗生物量、N和P吸收量及其吸收氮素来源的影响。结果表明:随着施氮量的增加,桉树幼苗植株生物量、N和P吸收量均显著增加。接种PGPR SZ7-1植物促生菌能显著促进桉树幼苗生物量的增加和养分量的吸收。未接种植物促生菌的桉树幼苗,其植株吸收氮素主要来源于土壤,其次是肥料;而接种PGPR SZ7-1植物促生菌的桉树幼苗,其植株吸收的氮素则主要来源于生物固氮。PGPR SZ7-1植物促生菌具有较好的固氮能力,固氮率达40%以上。结果还显示,随着施氮量的增加,接种植物促生菌的桉树幼苗生物固氮能力下降,植株氮素主要来源于土壤氮,其次为生物固氮和肥料氮。在较低的氮素水平下,接种植物促生菌能有效促进桉树植株的生长发育和养分吸收,是一种减少肥料施用、保护生态环境的农业措施之一。

The inoculating effect of plant growth-promoting rhizobacteria（PGPR） on Eucalyptus seedlings was studied on the different nitrogen levels using^15 N stable isotope tracer method. Plant height, biomass, nitrogen（ N）, Phosphate（ P） nutrient uptakes of Eucalyptus for seedlings were tested. The results showed that biomass,nitrogen（ N）, Phosphate（ P） nutrient uptakes of Eucalyptus for seedlings were significantly promoted with the increase of nitrogen applying. The effects of inoculating PGPR SZ7-1 on Eucalyptus for seedlings on the above parameters were also significant. The source of nutrient uptake was primarily from the soil for the seedlings of Eucalyptus without inoculation, while for the seedlings of Eucalyptus with inoculation, it was primarily from the biological nitrogen fixation, followed by the soil and the fertilizer. PGPR SZ7-1 has a high capacity of biological nitrogen fixation. The rates of nitrogen fixation were higher than 40% in this study. it was also found in the study that nitrogen fixation capacity of Eucalyptus for seedlings was decreased with the increase of nitrogen applying.The source of nitrogen uptake for the seedlings of Eucalyptus was more from the soil than the nitrogen fixation as the increasing of nitrogen. The study suggested that inoculating PGPR SZ7-1 on Eucalyptus seedlings was one of the good agricultural practices in the decreasing usage of fertilizers and the protection of the environment under a lower nutrient level.