Scots pines after exposure to elevated ozone and carbon dioxide probed by reflectance spectra and chlorophylla fluorescence transients

Natural Scots pines have been exposed to filtered air, ambient air and air with elevated O-3 or/and CO2 in open top chambers. The trees showed no differences in their optical responses prior to the fumigations. After the fumigation period of three months the plants were in good health. The position of the maximum derivative of the green light reflectance in carbon dioxide fumigated pines was shifted from the control pines inflection point, by approximately 4 nm towards shorter wavelengths. The position of the red edge derivative maximum showed no significant changes. By fluorescence techniques (as OJIP - fast fluorescence transients) nearly no change was found in the quantum yield for electron transport (phi(o) or excitation energy trapping phi(Po). However, the estimated activities as absorption, trapping or electron transport per cross-section increased considerably for all samples with elevated O-3 or CO2. This increased activity seems to be due to an increased antenna size in O-3 treated samples. At elevated CO2 the antenna size is decreased whereas the density of reaction centers per cross-section increased. This means that two different stress-adaptation mechanisms can lead to a similar macroscopic phenomenon like e.g. an increased metabolic activity.