著者

Reiji Fujimaki Takahiro Tateishi Ayato Kohzu Masanori Saito Naoko Tokuchi

出版者

Japanese Society of Soil Microbiology

雑誌

土と微生物 (ISSN:09122184)

巻号頁・発行日

vol.55, no.2, pp.121-128, 2001-10-01 (Released:2017-05-31)

参考文献数

21

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Arbuscular mycorrhizal (AM) colonization pattern in the roots of 4 plant species, Cryptomeria japonica (coniferous tree), Lindera triloba (deciduous shrub), Hydrangea hirta (deciduous shrub) and Leucosceptrum stellipilum (perennial herb), was investigated in a Japanese red cedar (C. japonica) forest on Mt. Ryuoh, central Japan. The AM colonization percentage was determined at different sampling sites along the slope. The AM colonization percentage in L. triloba was higher in the upper part of the slope than in the lower part. Topographic variations in soil nitrogen availability may have affected the AM colonization of the roots of L. triloba at the study site. However, other plants did not show such topographic changes in the AM colonization percentage. Microscopic observation of the morphological characteristics of AM colonization revealed that H. hirta and L. stellipilum were classified as Arum-type plants. In contrast, the mycorrhizas of C. japonica and L. triloba contained coiled hyphae to some extent as well as vesicles and arbuscules. Therefore, these two plants may be intermediate species between Arum- and Paris-type plants.

著者

渡辺 巌

出版者

Japanese Society of Soil Microbiology

雑誌

土と微生物 (ISSN:09122184)

巻号頁・発行日

vol.20, pp.1-10, 1978-12-15 (Released:2017-05-31)

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アカウキクサ(Azolla)は温帯,熱帯の池,水田に広く分布する水生羊歯植物でその上面葉下部の空腔中に窒素固定性藍藻Anabaena azollaeが共生し,無窒素培地で生育することができる。国際稲研究所内の圃場で1年間連続して22回のAzolla pinnataを栽培したところ,330日の生育期間で総計ha当り450kgの窒素をAzolla中に貯えることができた。この窒素固定力は熱帯マメ科牧草の窒素固定量年間最高値に近いものであり,共生藍藻細胞窒素当りの固定力もマメ科植物根粒中のバクテロイド細胞の値をはるかにこえるものである。Azollaは概して温帯性の種と分布が多いが,熱帯に分布するA. pinnataでも日平均気温22-27℃が最適で日最高気温の月平均が32℃をこすと,生育がおとろえる。高温に対する抵抗性が弱いことが熱帯での利用で問置になる。りん酸肥料の施用はAzollaの水田での生産にかかせない,過燐酸石灰の分施をすればP_2O_5 1kgで2kg以上の窒素をAzollaは生産できる。Azollaは中国,ベトナムでは広く水田緑肥として田植前後に水田で栽培されまた,堆肥源,動物飼料としても利用されている。国際稲研究所での近年の試験でも緑肥としての有効性が確認されたし,アジア諸国でもその利用が注目されはじめている。

著者

Katsuhiro Kojima Tadashi Yokoyama Naoko Ohkama-Ohtsu Suwat Saengkerdsub Manabu Itakura Hisayuki Mitsui Kiwamu Minamisawa Yasuhiro Arima

出版者

Japanese Society of Soil Microbiology

雑誌

土と微生物 (ISSN:09122184)

巻号頁・発行日

vol.66, no.1, pp.12-21, 2012-04-01 (Released:2017-05-31)

参考文献数

35

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Tetronic acid is a candidate for an inducer of nodulation (nod) gene expression in Mesorhizobium loti. However, there is no evidence that tetronic acid is secreted from Lotus species, the host plants of M. loti. This suggests that Lotus plants may produce other genuine nod gene inducers that differ from tetronic acid. In this study, M. loti cells harboring a nodA-lacZ fusion were enclosed in dialysis tubing and immersed in L. corniculatus culture solution. Significant β-galactosidase activities were detected in the M. loti cells, indicating that nod gene inducers were present in the seed and root exudates. β-galactosidase activities in M. loti cells were also determined after cells were exposed to seed and root exudates or tetronic acid in vitro. Seed and root exudates induced greater β-galactosidase activity in M. loti cells in 1 mM CaSO_4 solution than in YEM medium. In contrast, tetronic acid induced greater β-galactosidase activity in M. loti cells in YEM medium than in 1 mM CaSO_4 solution. Further, β-galactosidase activities induced by seed and root exudates and tetronic acid tended to decrease as the pH of the medium became neutral. In an LC-MS analysis, we could not detect tetronic acid in the concentrated seed and root exudates. These findings indicate that Lotus plants release genuine nod gene inducers for M. loti that differ from tetronic acid. Finally, seed exudates of L. corniculatus were fractionated according to molecular size and polarity, and it was clarified that a putative nod gene inducer in the seed exudates was a low molecular weight and high polarity substance.