Variation of 15N natural abundance in leaves and nodules of actinorhizal shrubs in Northwest Patagonia

• Published in: Symbiosis (Philadelphia, Pa.) Pa.), 2010, Vol.50 (1-2), p.97-105
• Main Authors: Chaia, Eugenia E, Myrold, David D
• Format: Article
• Language: English
• Subjects: Biomedical and Life Sciences; Developmental Biology; Discaria; Discaria chcaye; Discaria trinervis; Ecology; Evolutionary Biology; Frankia; leaves; Life Sciences; Microbiology; nitrogen; nitrogen content; nitrogen fixation; Ochetophila trinervisactinorhizas; Plant Sciences; Rhamnaceae; root nodules; stable isotopes; symbiosis
• ISSN: 0334-5114; 1878-7665
• DOI: 10.1007/s13199-009-0040-z

This study was performed to assess the N 2 -fixing capability of the native actinorhizal species Ochetophila trinervis (sin. Discaria trinervis ) and Discaria chacaye (Rhamnaceae) in Northwest Patagonia. We measured the N concentration and 15 N natural abundance in leaves and nodules of O. trinervis and D. chacaye, in leaves of associated non-actinorhizal vegetation, and in the soils under each sampled plant. O. trinervis and D. chacaye had foliar N concentrations that were about twice that of non-actinorhizal shrubs growing at the same sites, even though soils varied four-fold in total N across the sites. Leaves of both actinorhizal plants had a similar δ 15 N at any site and were close to atmospheric values. The foliar δ 15 N of non-actinorhizal plants and soil δ 15 N were strongly correlated across the sites. Nodules were depleted in δ 15 N relative to the foliage of the respective actinorhizal species. In conjunction with the uniformly high foliage N concentration of these actinorhizal plants and the universal presence of vesicles observed in root nodules, these data strongly suggest that O. trinervis and D. chacaye obtain a significant amount of their N from N 2 fixation. To calculate the proportion of N derived from atmosphere, theoretical B-values were estimated. In all cases where the δ 15 N of fixing and reference foliage were significantly different, O. trinervis and D. chacaye obtained almost all of their N from N 2 fixation. These results are the first to demonstrate N 2 fixation by O. trinervis and D. chacaye in the field and therefore suggest an important role for these actinorhizal plants in the N economy of ecosystems in northwest Patagonia as well as their potential use for restoration of degraded lands in this region.