Assessments of the overall release of reactive volatile organic compounds from vegetation require the knowledge of the effect of temperature and light intensity on emission rates. The aim of the study presented here was to investigate whether the rates of emission of the highly reactive sesquiterpene ¿-Caryophyllene (BCAR) from foliage of orange trees (Citrus sinensis (L.) OSBECK, var. Navel and Navel Late), detected using branch enclosures in an orange orchard in Spain, were not only temperature but also light dependent. We used two algorithms to calculate the diurnal variation of BCAR emission rates from environmental data. One algorithm accounted exclusively for the known exponential relationship between emission rate and temperature, and the other for both temperature and light effects. Assuming a light and temperature dependence of BCAR emission rates led to a more precise prediction of the short-term variation of BCAR emission rates than assuming that emissions are affected exclusively by temperature. The light dependence of BCAR emission rates could be due to a modulation of BCAR synthesis by light, or to an enhanced volatilization of BCAR from storage pools under high light exposure, or a combination of both. The data show that present assessments of the total release of reactive volatile organic compounds from vegetation, disregarding light effects on BCAR emission, are highly uncertain, if BCAR considerably contributes to total terpenoid emissions of the investigated plants.