Figure 6.

Summary of relationship between the carbon isotopic composition of CO₂ in the dynamic headspace atmosphere(¹³CO₂, % total) and the percentage of leaf isoprene emitted as [¹²C]isoprene and [¹³C_1–3]isoprene during (a) [¹³C]methanol; (b) [¹³C₂]formaldehyde; (c) [¹³C]formate; (d) [2-¹³C]glycine; and (e) [¹³C₂]acetate labeling of detached I. edulis branches via the transpiration stream. Also shown in (f) is the linear relationship observed between the percentage of ¹³CO₂ during the labeling experiments and the corresponding percentage of [¹³C₁]isoprene emissions relative to total isoprene emissions. Note that isotopic analysis of CO₂ was not available during the [¹³C]formaldehyde labeling experiments.