Drought stress affects temperature response of leaf dark respiration in Mediterranean coastal maquis species

Leaf dark respiration (R-D) plays a key role in plant carbon balance and the knowledge about how environmental stresses affect the response of R-D to temperature under field conditions, might improve the reliability of carbon budget models. This study analyzed the influence of air temperature and drought on the short-term temperature response of R-D of three woody ever green Mediterranean species. The field activities were carried out in two different coastal sites of Italy and for each site, two different areas located near the shoreline and inland were considered. The respiration-temperature response curves were carried out seasonally, together with leaf water potential and sclerophyll degree measurements. The effect of the average air temperature of the previous two days (T-2m) and predawn water potentials on basal respiration measured at 18 degrees C (R-18) and temperature sensitivity (Q(10)), were tested with linear regression analysis. Both R-18 and Q(10) were weakly correlated with T-2m, while a multifactor model including predawn water potentials yielded a better relation. These findings suggest that, besides air temperature, water availability and in general, plant energy balance, must be taken into account to predict acclimation of leaf dark respiration.