Primary photosynthetic processes in two forest tree species subjected to long-term elevated CO2 concentration
Abstract
The long-term CO2 enrichment usually causes significant stimulation of photosynthesis in forest trees. However, the response of individual parts of photosynthetic processes to elevated CO2 is still not completely elucidated.
We studied the impact of long-term exposure of young beech and spruce trees to elevated CO2 on the efficiency of primary photosynthetic processes using in situ measurements of the polyphasic rise of chlorophyll a fluorescence transient (OJIP curve) and in vitro measurements of the Photosystem 1 and 2 activities in suspensions of isolated chloroplasts. Our results showed that a) the CO2 enrichment can negatively affect the efficiency of electron-transport processes in thylakoid membranes; b) this effect can be observed only in the sun-exposed leaves in contrast to the shaded ones; c) young leaves (sampled in June / July) are more affected than the older ones (sampled in August / October).