Extended Data Fig. 7: ¹³C enrichment of isoprene and (−)-α-pinene.

a, ¹³C enrichment of isoprene measured with PTR-TOF-MS shows substantial enrichment above pre-pulse levels on the day of the labelling pulse but not on the days following the labelling pulse. b, A section of the chromatogram obtained from the GC-IRMS showing the peaks for the identified compounds. c, A section of the chromatogram obtained from the GC-IRMS showing the trans-β-ocimene peaks. The integrated regions are shaded in grey. d, A section of the chromatogram obtained from the GC-IRMS showing the β-myrcene peak. The integrated region is shaded in grey. e, Box plots representing the ¹³C enrichment of (−)-α-pinene. Each method represents a different way of integrating the (−)-α-pinene peak in the GC-IRMS chromatogram. The integration method is depicted in the subplot above the box plots. For a and e, the grey boxes represent the standard deviation of the values of the compounds in ambient air when there is no ¹³CO₂ pulse. The black line through the grey boxes represents the mean. The box plots present the median, and 25th and 75th percentiles. The small squares represent the mean and the whiskers represent the maximum and minimum acquired data points that are not considered as outliers. Significant results are indicated by the asterisk (*) above the box (that is, results are significant if P ≤ 0.05). Statistical information for e is shown in Extended Data Table 3b.