Foliage of Scots pine (Pinus sylvestris L.) and pedunculate oak (Quercus robur L.) was collected in a mixed pine/oak forest at canopy positions differing in radiation environment. In both species, chlorophyll (Chl) a/b ratios were higher in foliage of canopy positions exposed to higher irradiance as compared to more shaded crown layers. Throughout the growing season, pine needles exhibited significantly lower Chl a/b ratios than oak leaves acclimated to a similar photon availability. Hence, pine needles showed shade-type pigment characteristics relative to foliage of oak. At a given radiation environment, pine needles tended to contain more neoxanthin and lutein per unit of Chl than oak leaves. The differences in pigment composition between foliage of pine and oak can be explained by a higher ratio of outer antennae Chl to core complex Chl in needles of P. sylvestris which enhances the efficiency of photon capture under limiting irradiance. The shade-type pigment composition of pine relative to oak foliage could have been due to a reduced mesophyll internal photon exposure of chloroplasts in needles of Scots pine, resulting from their xeromorphic anatomy. Hence, the higher drought tolerance of pine needles could be achieved at the expense of shade tolerance. and U. Hansen, J. Schneiderheinze, B. Rank.
Photoinhibitory fluorescence quenching, qjjj, was detected in šitu in a montane spruce forest using a non-destructive chloropbyll fluorescence method combined with parallel sampling of light and temperature data. occuired as a common phenomenon in this type of ecosystem, altbougb low irradiances (LI) were tfae major factor limiting the growth. Under the prevailing LI photoinhibition was due to the suboptimal temperatures rather than irradiance. The found pattem of photoinhibitory fluorescence quenching is supposed to be characteristic of measuring sites in this montane region, where high irradiance (HT) is rare, but if it occurs, then it is along with a high temperature.