Fig. 3.
Correlations among the initial quantum yield of isoprene emission [αI in Eq. 2; (a, b)], and isoprene emission rate at a high light of Q = 1000 μmol m-2 s-1 (c, d) with DMADP pool size (a, c) and isoprene synthase rate constant (b, d) in different-aged leaves of hybrid aspen (P. tremula x P. tremuloides). Estimation of DMADP pool size (SDMADP) and isoprene synthase rate constant (k) as in Fig. 2. In (a), an average SDMADP for Q values of 250 and 500 μmol m-2 s-1 was used, while in (b), an average SDMADP for Q values of 500 and 1850 μmol m-2 s-1 was used. In (b) and (d), k is an average for all three light intensities because k did not vary with Q (Fig. 2). Data were fitted by linear and non-linear regressions (P < 0.01 for all regressions shown by solid lines, P < 0.1 for the regression shown by a dotted line in (a) and P > 0.2 for the regression shown by a dotted line in (c). In the regressions in (a) and (c), young and mature leaves were pooled, while in (d), old and mature leaves were pooled.