Variations in leaf respiration across different seasons for Mediterranean evergreen species

Leaf respiration (R (L)) of evergreen species co-occurring in the Mediterranean maquis developing along the Latium coast was analyzed. The results on the whole showed that the considered evergreen species had the same R (L) trend during the year, with the lowest rates [0.83 +/- 0.43 mu mol(CO2) m(-2) s(-1), mean value of the considered species] in winter, in response to low air temperatures. Higher R (L) were reached in spring [2.44 +/- 1.00 mu mol(CO2) m(-2) s(-1), mean value] during the favorable period, and in summer [3.17 +/- 0.89 mu mol(CO2) m(-2) s(-1)] during drought. The results of the regression analysis showed that 42% of R (L) variations depended on mean air temperature and 13% on total monthly rainfall. Among the considered species, C. incanus, was characterized by the highest R (L) in drought [4.93 +/- 0.27 mu mol(CO2) m(-2) s(-1)], low leaf water potential at predawn (I-pd= -1.08 +/- 0.18 MPa) and midday (I-md = -2.75 +/- 0.11 MPa) and low relative water content at predawn (RWCpd = 80.5 +/- 3.4%) and midday (RWCmd = 67.1 +/- 4.6%). Compared to C. incanus, the sclerophyllous species (Q. ilex, P. latifolia, P. lentiscus, A. unedo) and the liana (S. aspera), had lower R (L) [2.72 +/- 0.66 mu mol(CO2) m(-2) s(-1), mean value of the considered species], higher RWCpd (91.8 +/- 1.8%), RWCmd (82.4 +/- 3.2%), I-pd (-0.65 +/- 0.28 MPa) and I-md (-2.85 +/- 1.20 MPa) in drought. The narrow-leaved species (E. multiflora, R. officinalis, and E. arborea) were in the middle. The coefficients, proportional to the respiration increase for each 10A degrees C rise (Q(10)), ranging from 1.49 (E. arborea) to 1.98 (A. unedo) were indicative of the different sensitivities of the considered species to air temperature variation.