The annual course of certain parameters that characterize the photosynthetic behavior of leaves was derived from diel courses of CO 2 gas exchange and transpiration of intact Arbutus unedo leaves during the period August 1982 to September 1983. The diel courses were shown in a preceeding paper. These data were analyzed along with microclimatic conditions and plant water status and led to the following: — The daily rate of CO 2 uptake (NP ges ) increased steadily from very low rates during the summer dry period throughout the autumn and winter. In February the rates were about eight fold greater than at the end of the dry period. The new leaves, which flushed in March, exhibited these high rates by April and remained at this level of activity until the end of May. At this time midday stomatal closure was first apparent and NP ges decreased throughout the summer to similar rates as were found at the end of the dry period in the previous year. — The total daily water loss (Tr ges ) was very low during the two dry periods. It increased slightly in autumn due to the greater stomatal conductance and remained at a comparatively low level throughout the winter because of the small water saturation deficit of the air at this time of year. The increase in air temperature in spring along with plentiful soil moisture resulted in a steep increase in Tr ges . From the end of May, Tr ges decreased steadily until the end of the dry period. — Due to the very effective stomatal regulation of water loss, the transpiration ratio (TQ = Tr ges /NP ges ), exhibited comparatively low values (similar to those, which were found in early spring) during the two dry periods. The lowest values occurred during the winter. Rather high values were found in the late spring as well as on some days following rain during the dry period, in which case the plants did not exhibit the coordination between stomatal aperture and photosynthetic activity in the mesophyll as was usually exhibited. — The daily maximum rates of net photosynthesis (NP max ) and transpiration (Tr max ) were linearly correlated with NP ges and Tr ges , respectively. Therefore, they can be considered as representative parameters for the annual course of CO 2 gain and transpiration. During the winter, NP max and the daily maximum of photosynthetically active radiation (PAR max ) occurred frequently at the same time of day because photosynthesis was usually light limited at that time of year. From late spring and through the summer, the NP max occurred progressively earlier in the day, since the stomata began to close during the morning hours as water stress became more pronounced. Throughout the year, NP max occurred always within the same temperature range of about 25°C and at almost the same water vapour pressure deficit between leaf and air (ALVPD), about 14 mbar bar − 1 . Thus, stomatal control of transpiration seems to occur only at values greater than 14 mbar bar − 1 . From these data it can be concluded, that the photosynthetic apparatus seems to behave rather “conservatively” in relation to the annual fluctuation of ambient conditions. An important aspect of acclimation to these annual fluctuations is accomplished by stomatal control, which shifts the main period of photosynthetic activity to different times of day when the most favourable ambient conditions occur. — NP max and the respective stomatal conductance (G NPmax ) were linearly correlated. Therefore, following normal diffusion law assumptions, NP max always occurred at similar internal CO 2 partial pressure (p i ≈ 208 μ bar). — During the dry period, NP max as well as G NPmax were approximately linear correlated with the predawn water potential ( ψ pd ). During the rest of the year there was no apparent correlation of these two parameters with the water status of the plants. — There was no marked correlation between the annual course of TQ and that of Because of the effective stomatal control of water loss during the dry period, TQ was similar in the summer ( ψ pd < —45 bar) and in the winter ( ψ pd = —10 bar). — A short term improvement of plant water conditions following rain during the dry period resulted in only a temporary increase of stomatal conductance but no marked increase of photosynthetic activity.