Document: TAL-3-30-4

Within and among population variation in acclimation to light in white spruce.

AWADA, T.* ¹ and R.E.REDMANN ²

University of Nebraska, Lincoln, NE USA ¹
University of Saskatchewan, Saskatoon, SK, Canada ²

Abstract:
Physiological responses to sun and shade treatments in the greenhouse were examined in white spruce (Picea glauca) seedlings collected from three naturally-regenerated (N1, N2 and N3) and three planted (P1, P2, and P3) stands in the mixedwood boreal forest of central Saskatchewan, Canada. Seedling survival was greater in the sun than in the shade. Dark respiration, light compensation point and quantum yield declined by 70, 81 and 45 % respectively, in shade- compared to sun-acclimated seedlings. Total chlorophyll content and specific leaf area increased by 33 and 32%, respectively, in response to shade. At light saturation, populations P1 and N3 showed similar photosynthetic responses (about 6 micro mol m^-2 s^-1) under both light regimes. Populations P2, P3 and N2 performed poorer in the sun than in the shade (8.2, 8.7 and 9.1 in shade, versus 5.1, 4.1 and 5.5 mol m^-2 s^-1 in full sun, respectively). Photosynthetic rate in N1 was greater in sun than in shade (14.7 11.1 mol m^-2 s^-1, respectively). Differences in physiological responses to light among populations suggest the presence of more than one ecotype. N1 behaved like a true "sun population", showing the greatest plasticity in the measured parameters, while the remaining populations behaved more like shade-adapted populations. Intra-population variation in physiological parameters was large for both regeneration types. It appears that selection pressure during reforestation was not great enough to cause a decline in intra-population variation in planted compared to naturally-regenerated white spruce seedlings.

Keywords: white spruce, light acclimation, boreal forest.

This abstract is being presented at: 4:45 PM in session:
Oral Session #10: Light Relations in Plants.