PHYSIOLOGICAL-ACTIVITY, IN A SEMI-ARID ENVIRONMENT, OF EUCALYPTUS-CAMALDULENSIS DEHN FROM 2 PROVENANCES

Physiological activity including 14CO2 uptake, growth, stomatal conductance and evapotranspiration of E. camaldulensis Dehn. trees from 2 seed sources were compared: one from the tropical climate of northern Australia (Katherine) and the other from the dry subtropical climate of southern Australia (Lake Albacutya). The trees were grown in the semiarid climate (rainless summer) of southern Israel. Diurnal measurements were made on 9 occasions during the winter and summer of 1974/1975 on 4 yr old seedling trees. Physiological activity was low before the rains started. After the onset of rains renewal of activity was first detected in the Katherine provenance seedlings but after a short period the Lake Albacutya provenance seedlings showed higher rates of activity, reaching maximum midday rates of stomatal conductance and CO2 uptake of 2.2 mm s-1 and 0.24 mg m-2 s-1, respectively. Activity during the summer of 1975 was very low but CO2 uptake and stomatal conductance after the rains of winter 1975/1976 returned to the levels observed in the previous winter. The growth of seedlings of the 2 provenances, as indicated by the cumulative change in stem diameter, was well correlated with the evapotranspiration. Growth of the Katherine provenance seedlings did not recover after a dry period during the 2nd winter. The seedlings which originated in the cooler and drier region of Australia were adapted to the semiarid conditions of southern Israel than were those from the tropical region, although the aridity of the region imposed severe restaints on the growth of both provenances.