Effect of mineral nutrient content on oxygen exchange and chlorophyll a fluorescence in needles of Norway spruce
1997
Strand, M.
Photosynthetic O2 evolution at high irradiances (approximately 600-1000 micromoles m-2 s-1) and O2 uptake in darkness were measured in needles of control, irrigated and irrigated-fertilized trees of Norway spruce (Picea abies (L.) Karst.). Measurements were made at 20 degrees C and at high CO2 concentrations. The results suggest that, at given times of the year, a major part of the variation in gross photosynthesis of current-year and one-year-old needles across treatments is associated with differences in needle N content. Furthermore, the rate of O2 uptake measured after 5 or 10 min in darkness was positively correlated with both the preceding rate of gross O2 evolution and the N content in fully expanded current-year needles. Measurements of chlorophyll alpha fluorescence, taken simultaneously with measurements of O2 evolution in current-year sun needles, showed that Stern-Volmer quenching of minimum fluorescence and the ratio of variable to maximum fluorescence in the dark- and light-adapted state were strongly correlated with the gross rate of O2 evolution. This suggests that the increased rate of gross photosynthesis in needles of irrigated-fertilized trees was associated with adjustments in the thermal energy dissipation within photosystem II.
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