Foliar and cortical terpene profile, and needle gas exchange and water potential of P. halepensis, P. brutia and P. eldarica were compared over three consecutive seasons (1996-1998) in an experimental plantation nearby Firenze (Italy). Terpene percentages in mature tissue (cortex and needle) did not change in response to water stress during summer period and remained stable through seasons and years. Terpene profiles were not affected by seasonal drought, and are thus valuable to characterize Mediterranean pine species of the group “halepensis”. There was a threshold-type response of maximum daily gas exchange to decreasing predawn water potential in all pines. Net photosynthesis and needle conductance were linearly related, regardless of the species
