© 1997 Heron Publishing—Victoria, Canada
Effect of mineral nutrition content on oxygen exchange and chlorophyll a fluorescence in needles of Norway spruce
Martin Strand
Department of Forest Genetics and Plant Physiology, The Swedish University of Agricultural Sciences, S-901 83 Umeå, Sweden / Received June 27, 1996
Summary
Photosynthetic O2 evolution at high irradiances (approximately 600–1000 µmol 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 °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 a 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.
Keywords:
dark respiration, fertilization, fluorescence quenching, leaf nitrogen, photosynthesis, Picea abies.
