Control Mechanisms of Photosynthetic Capacity Under Elevated CO2 Concentration: Evidence from Three Experiments with Norway Spruce Trees

摘要: Twelve-year-old Norway spruce (Picea abies [L.] Karst.) were exposed to ambient (AC) or elevated (EC) [ambient + 350 μmol(CO2) mol−1] CO2 concentration [CO2] using the facilities of open-top-chambers (OTCs) and glass domes (GDs). A combination gas exchange measurements application a biochemical model photosynthesis used for evaluation assimilation characteristics. Morphological change was assessed on base specific leaf area (SLA). Nitrogen (N) content in apparatus considered main factor influencing capacity. Three experiments confirm hypothesis that an adjustment photosynthetic capacity under EC is controlled by biochemical, morphological, physiological feedback mechanisms. We observed periodicity down-regulation (Experiment No. 1) during vegetation seasons. In spring months (May–June), i.e. occurrence active carbon sink associated with formation new foliage, up-regulation (10–35 %) (PNsat) observed. On contrary, autumn (September–October) (25–35 PNsat recorded mainly reduced strength change, decrease N status (up 32 accumulation saccharides 72 leaves. Different adjustments activities current (C) one-year-old (C-1) needles 2). Strong diminution initial stimulation rate (PNmax) decreases both ribulose-1,5-bisphosphate carboxylase/oxygenase carboxylation activity (by RuBP regeneration 40 %). This performance tightly correlated absence sinks, content, starch C-1 needles. Finally, different responses sun- shade-adapted 3) balance between morphological changes. Observed 22 predominantly caused effects higher assimilate stronger dilution, resulting from absolute rates incident irradiances upper canopy.