Figure 4.

Dependencies of the rates of net assimilation, isoprene emission, and transpiration (A) and the size of the chloroplastic DMADP pool (B) on ambient CO₂ concentration (C_a) at saturating light (550 μmol m⁻² s⁻¹) and ambient O₂ concentration (210 mmol mol⁻¹) in hybrid aspen leaves. Leaf temperature was 28°C to 30°C. CO₂ concentration in the substomatal cavities was 26 μmol mol⁻¹ at the lowest C_a and 1,230 μmol mol⁻¹ at the highest C_a (calculated from stomatal conductance, assimilation rate, and C_a). The inset in B demonstrates the dependence of isoprene emission rate on DMADP pool size. Chloroplastic DMADP pool size was estimated on the basis of an in vivo method using postillumination isoprene release (Rasulov et al., 2009). Error bars show sd (n = 5).