Differences in photosynthetic activity, chlorophyll and carotenoid levels, and in chlorophyll fluorescence parameters in green sun and shade leaves of Ginkgo and Fagus

The differences in pigment levels and photosynthetic activity of green sun and shade leaves of ginkgo (Ginkgo biloba L.) and beech (Fagus sylvatica L.) are described. Sun leaves of both tree species possessed higher levels in chlorophylls (Chl) and carotenoids on a leaf area basis, higher values for the ratio Chl a/b and lower values for the ratio Chl/carotenoids (a+b)/(x+c) in comparison to shade leaves. The higher photosynthetic rates PN of sun leaves (ginkgo 5.4±0.9 and beech 8.5±2.1 μmolm−2 s−1) were also reflected by higher values for the Chl fluorescence decrease ratios image690 and image735. In contrast, the shade leaves had lower PN rates (ginkgo 2.4±0.3 and beech 1.8±1.2 μmol m−2 s−1). In both tree species the stomatal conductance Gs was significantly higher in sun (range: 70–191 mmolm−2 s−1) as compared to shade leaves (range: 5–55 mmol m−2 s−1). In fact, at saturating light conditions there existed a close correlation between Gs values and PN rates. Differences between sun and shade leaves also existed in several other Chl fluorescence ratios (Fv/Fm, Fv/Fo, and the stress adaptation index Ap). The results clearly demonstrate that the fan-shaped gymnosperm ginkgo leaves show the same high and low irradiance adaptation response as the angiosperm beech leaves.