The effect of age on the photosynthetic rate inPrunus laurocerasus L. leaf discs

The photosynthetic rate in leaf discs (P _LD) ofPrunus laurocerasus L. plants taken up from leaves of various ages was measured under constant temperature (20±0.5°C) CO₂ concentration in air (0.03%) complete water saturation and irradiance (71 W m² PhAR). TheP _LD is the highest in mature leaves of the current year. The extent of depression in the second and further years depends on the degree of habitat shading. In a slightly shaded habitat (60 to 73% daily sum of photosynthetically active radiation—PhAR) it decreases by almost 50% in the second year. In a deeply shaded habitat (22.5–28.2% daily sum PhAR) the depression amounts to 31.7% in the second year in the third and fourth years to 61.7 and 73.2% respectively.