Fig. 5. Linear regression and matched pairs statistical analyses of nitrate additions to an oven-dried tissue extract. For each method (FIA, flow injection analysis; M-NaR, laboratory microplate nitrate reductase kit; TSR; test strip reflectometry; ISE-card, ion specific electrode card), the nitrate concentration of untreated extract was subtracted from the treated extracts and the adjusted nitrate concentrations of the extract regressed against results obtained for nitrate in deionized H2O.