Figure 1.

Stomatal conductance rates in leaves of P. australis (isoprene emitter, circles) and Q. ilex (monoterpene emitter, triangles). The increment of stomatal conductance after inhibiting isoprenoid formation (x axis, values expressed as percent of the stomatal conductance in the same leaves before isoprene inhibition [=100]) is plotted versus the stomatal conductance rates of each leaf, measured before isoprenoid inhibition (y axis). Isoprene was inhibited by feeding 20 μm fosmidomycin through petioles. In some leaves of P. australis (black squares) the increment of stomatal conductance after endogenous isoprene inhibition was again measured after reconstituting the internal pool with exogenous isoprene (3 ppm of gaseous isoprene in the air flowing over the leaf in the gas exchange cuvette) for 1 h (white squares).