© 2003 Heron Publishing—Victoria, Canada
Light-energy processing and freezing-tolerance traits in red spruce and black spruce: species and seed-source variation
John E. Major (1, 2), Debby C. Barsi (1), Alex Mosseler (1), Moira Campbell (1) and Om P. Rajora (1, 3)
1. Natural Resources Canada, Canadian Forest Service—Atlantic Forestry Centre, P.O. Box 4000, Fredericton, NB E3B 5P7, Canada / 2. Author to whom correspondence should be addressed (jmajor@nrcan.gc.ca) / 3. Department of Biology, Life Sciences Centre, Dalhousie University, Halifax, NS B3H 4J1, Canada / Received November 7, 2002; accepted January 17, 2003; published online June 2, 2003
Summary
Red spruce (Picea rubens Sarg.) and black spruce (Picea mariana (Mill.) B.S.P.) are genetically and morphologically similar but ecologically distinct species. We determined intraspecific
seed-source and interspecific variation of red spruce and black spruce, from across the near-northern margins of their ranges,
for several light-energy processing and freezing-tolerance adaptive traits. Before exposure to low temperature, red spruce
had variable fluorescence (Fv) similar to black spruce, but higher photochemical efficiency (Fv/Fm), lower quantum yield, lower chlorophyll fluorescence (%), and higher thermal dissipation efficiency (qN), although the seed-source effect and the seed-source × species interaction were significant only for Fv/Fm. After low-temperature exposure (–40 °C), red spruce had significantly lower Fv/Fm, quantum yield and qN than black spruce, but higher chlorophyll fluorescence and relative fluorescence. Species, seed-source effect, and seed-source
× species interaction were consistent with predictions based on genetic (e.g., geographic) origins. Multi-temperature exposures
(5, –20 and –40 °C) often produced significant species and temperature effects, and species × temperature interactions as
a result of species-specific responses to temperature exposures. The inherent physiological species-specific adaptations of
red spruce and black spruce were largely consistent with a shade-tolerant, late-successional species and an early successional
species, respectively. Species differences in physiological adaptations conform to a biological trade-off, probably as a result
of natural selection pressure in response to light availability and prevailing temperature gradients.
Keywords:
adaptive traits, chlorophyll fluorescence, ecophysiology, fitness, genetic variation, Picea mariana, Picea rubens, photosynthesis.
