Fig. 2. Seasonal pattern of the slope (PhRUE) of the relationship between net CO₂ assimilation and incident PAR, both integrated over a day, for individual leaves of almond and walnut. The slopes were calculated both with data on all sampled leaves (PhRUE_50L, circles) and for a hypothetical leaf at the top of the canopy (PhRUE_HL, solid line). Bars indicate the 95% confidence limits of the slopes (i.e. PhRUE_50L).