A model coupling foliar monoterpene emissions to leaf photosynthetic characteristics in Mediterranean evergreen Quercus species

Summary•  A model was developed and parameterized to simulate monoterpene emission rates per unit leaf area ( E ) dependent on foliar photosynthetic potentials and activity of monoterpene synthases in the evergreen sclerophylls Quercus coccifera L. and Q. ilex L. •  Assuming that total activity of monoterpene synthases controls the pathway flux, the product of leaf dry mass per unit area E was culculated as the fraction of total electron flow used for monoterpene synthesis (ɛ), the rate of photosynthetic electron transport ( J ) per unit leaf dry mass and the reciprocal of the electron cost of monoterpene synthesis. In the model, light effects on E result from light responses of J , and the temperature relationship of E combines temperature dependencies of J and the specific activity of monoterpene synthase ( S S ). •  Having determined J from leaf photosynthesis data and deriving an estimate of S S from in vitro laboratory measurements, good fits to diurnal time‐courses of monoterpenoid emission rates were obtained using a single leaf‐dependent coefficient, the total monoterpene synthase activity in the leaves. •  Our analysis demonstrates that using J as a surrogate of E leads to a realistic description of E , especially under stress conditions where the previous models fail. However, analysis of daily time courses of E indicated that storage of monoterpenoids in nonspecific leaf compartments might alter the correspondence between monoterpenoid synthesis and emission rates, especially after rapid environmental change.