Heterotrophic N₂-fixation contributes to nitrogen economy of a common wetland sedge, <i>Schoenoplectus californicus</i> - Fig 2

<p>Relationship between rhizome nitrogenase activity and rhizome δ¹⁵N (A) and shoot and rhizome δ¹⁵N (B) in <i>Schoenoplectus californicus</i> from Lake Atitlán; full diamond–unpolluted sites, empty diamonds–polluted sites. Each nitrogenase activity value is a mean of 3–4 replicates, isotope data were measured on pooled samples. Nitrogenase activity expressed as ethylene production (nmol C₂H₄ gDW^-1 d^-1).