© 2000 Heron Publishing—Victoria, Canada
Chlorophyll fluorescence and CO2 assimilation of black spruce seedlings following frost in different temperature and light conditions
M. Lamontagne (1, 3), F. J. Bigras (2) and H. A. Margolis (1)
1. Centre de recherche en biologie forestière, Pavillon Abitibi-Price, Université Laval, Sainte-Foy, Québec G1K 7P4, Canada / 2. Ressources naturelles Canada, Service canadien des forêts, Centre de foresterie des Laurentides, 1055, rue du P.E.P.S., C.P.
3800, Sainte-Foy, Québec G1V 4C7, Canada / 3. École de sciences forestières, Université de Moncton, Campus d'Edmundston, Edmundston, NB E3V 2S8, Canada / Received February 23, 1999
Summary
Effects of artificial frosts on light-saturated photosynthesis (Amax) and ground, maximal and variable fluorescence variables (Fo, Fm, and Fv and Fv/Fm) were monitored on 1-year-old foliage of black spruce seedlings (Picea mariana (Mill.) BSP) grown at high (25 °C), moderate (15 °C) and low (5 °C) temperatures and moderate (240 μmol m–2 s–1) and low (80 μmol m–2 s–1) irradiances. Photoinhibition of 1-year-old foliage was greater in seedlings grown in moderate light than in seedlings grown
in low light. Photoinhibition increased with decreasing growth chamber temperature at both irradiances. Most changes in Fv/Fm were caused by changes in Fv. Exposure to –4 °C decreased both Fv/Fm and Amax compared with control values. The effect of the –4 °C frost treatment was greater in seedlings grown in low light than in
seedlings grown in moderate light, probably because seedlings grown in moderate light were already partially photoinhibited
before the frost treatment. Following –4 °C treatment, neither Fv/Fm nor Amax recovered in seedlings grown in low light. Light-saturated photosynthesis decreased with decreasing growth chamber temperature.
Light-saturated photosynthesis was more sensitive to the –3 and –4 °C frost treatments in seedlings grown at 25 °C than in
seedlings grown at 15 and 5 °C. The Amax of seedlings grown at 15 °C was sensitive only to the –4 °C frost treatment, whereas Amax of seedlings grown at 5 °C was not sensitive to any of the frost treatments. Recovery of Amax following frost took longer in seedlings grown at high temperatures than in seedlings grown at low temperatures. For seedlings
grown at the same temperature but under different irradiances, both Amax and Fv/Fm reflected damage to the photosynthetic system following a moderate frost. However, for seedlings grown at the same irradiance
but different temperatures, Amax provided a more sensitive indicator of frost damage to the photosynthetic system than Fv/Fm ratio.
Keywords:
conifer, fluorescence, frost damage, frost hardiness, photoinhibition, Picea mariana.
