| Co-Investigator(Kenkyū-buntansha) |
TAMAI Yutaka Hokkaido University, Res.Fac.of Agriculture, Associate Professor (50281796)
HARAGUCHI Akira Universityof Kitakyushu, Fac.of Environmental Engineering, Professor (50271630)
MATSUURA Hideyuki Hokkaido University, Res.Fac.of Agriculture, Associate Professor (20344492)
IWAHASHI Hitoshi National Institute of Advanced Industrial Science and Technology, Human Stress Signal Research Center, Institute Head (60356540)
TAWARAYA Keitarou Yamagata University, Fac.of Agriculture, Professor (70179919)
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| Research Abstract |
Using local peat soil from Central Kalimantan, Indonesia, a saprophytic soil fungus Penicillium sp. Isolate Y-1 from X. complanata seedbed was tested its seed-germination promotion activity. The seeds germinated well by means of inoculation with Y-1 fungus, but the resulting seedlings were all died after one month-incubation in the local peat soil bed. Only when the supernatant of the local soil suspension without sterilization was further inoculated to the seedbeds, the germinated seedlings that had been inoculated with Y-1 resulted in survival and normal growth of the seedlings over 6 month. This suggested that saprophytic fungi stimulate seed germination, while some soil bacteria provide nutrients to the germinated seedlings. On the other hand, in Siberian Taiga forest bed soil, oligotrophic Burkholderia and Pseudomonas occupied soil microflora, and they showed a relatively high acetylene reduction activity at 10-15℃,under a lower concentration of carbon source (0.02-0.05%). Including medium pH, these soil bacteria were highly adapted to culture conditions agreeable to the permafrost soil, so that physicochemical conditions similar to activated permafrost soil in summer seasons resulted in relatively higher nitrogen-fixing activity. Moreover, gellan gum as gel matrix allowed the bacteria to show maximal nitrogen-fixing potential. Under a field condition of newly accumulated volcanic ash soil accumulated extreme soil land in Mt. Usu, Hokkaido, the land allowed pioneer plants to possess mycorrhizal symbionts and grew dominantly. Particularly, those of willow tree saplings constitutively possessed ectomycorrhizal fungi, while herbivorous weeds, except horsetail and rasp, allowed symbiosis with arbuscular mycorrhizal fungi. Thus, it was found that pioneer plants distributing throughout fresh volcanic ash soil in Mt. Usu were dependent on mycorrhizal infection.
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