How growth conditions affect the capacity of Quercus ilex leaves to emit monoterpenes

Summary•  The effects of climate conditions on foliar monoterpene emissions from Quercus ilex saplings were studied in new leaves grown at two temperature regimes combined with two light regimes and by acclimatizing them to new regimes once leaves were mature. •  Both high light and warmth strongly promoted the foliar emission capacity, E S (i.e. the steady‐state emission rate measured at standard conditions), of developing and mature leaves, but did not significantly change the emission composition. The E S values of leaves adapted to warm and high‐light conditions were one order of magnitude higher than that of leaves adapted to cool and shaded conditions. •  The acclimatizations of E S in mature leaves to new regimes proceeded over a few days to a few weeks and were often paralleled by changes in photosynthesis. Under unchanged regimes, the E S of mature leaves remained stable in high‐light adapted leaves and decreased somewhat in shade adapted leaves. •  The findings suggest that the spatial variation in foliar E S within a tree canopy results from the direct influence of the leaf microclimate rather than from leaf structural properties, and that in the course of the year, the E S of leaves will repeatedly be upregulated and downregulated according to the prevailing temperature and light conditions, which may be accompanied by a slight attenuation of E S related to leaf age.