シモノ　アヤコ   Shimono Ayako   下野　綾子    所属   東邦大学  理学部 生物学科    職種   准教授
論文種別	原著
言語種別	英語
査読の有無	査読あり
表題	Tracking the route of atmospheric nitrogen to diazotrophs colonizing buried mangrove roots
掲載誌名	正式名：Tree Physiology
掲載区分	国外
出版社	Oxford Academic
巻・号・頁	39(11),pp.1896-1906
著者・共著者	Inoue, T., Kohzu, A., and Shimono, A.
発行年月	2019/11/18
概要	Nitrogen-fixing activity has been observed in the rhizosphere of mangrove ecosystems, suggesting a close mangrove–diazotroph relationship. In regularly flooded soil, however, the pathway by which atmospheric nitrogen reaches the diazotrophs in the rhizosphere is unknown. This study provides evidence that mangrove aerial roots serve as pathways that supply nitrogen gas to the diazotrophs colonizing buried roots. A plastic chamber was attached on the exposed part of a Rhizophora stylosa Griff prop root, and 15N2 tracer gas was injected into it. The entire root, including the below-ground part, was collected for analysis of 15N labelling and nitrogenase activity. We detected 15N labelling in buried root materials 2 h after gas injection. Compared with the δ15N contents in root material from an untreated tree, the increment was >10‰ in lateral roots. The nitrogenase activity measured on the other R. stylosa roots was highest in lateral roots, matching well with the results of 15N labelling. Our results indicate that atmospheric nitrogen is taken into aerial mangrove roots through lenticels, diffuses into the buried root system and is fixed by diazotrophs. The unusual appearance of mangrove aerial roots, which has intrigued researchers for many years, could be a key to the high productivity of mangrove ecosystems.