The influence of light quality and carbon dioxide enrichment on the growth and physiology of seedlings of three conifer species .2. Physiological responses

Pinus banksiana, Picea mariana, and Picea glauca were grown at 350, 700, or 1050 mu L . L(-1) CO2 and either high or low red/far-red quantum flux ratios. After a 16-week, long day growth period, seedlings were subjected sequentially to short daylengths, then short days with low temperatures. Various physiological parameters were determined at the end of each treatment phase to monitor how those treatments influenced the onset of seedling dormancy. After the long day treatments, high ratios increased the total chlorophyll content and reduced the original level of chlorophyll fluorescence and the shoot total nonstructural carbohydrate content in very shade-intolerant Pinus banksiana. In shade-tolerant Picea mariana, high CO2 levels caused the main effects on these parameters while neither light quality or CO2 had significant effects on them in shade-tolerant Picea glauca. Short days and low temperature induced a proportional increase in the partitioning of total nonstructural carbohydrate to the roots in all species and produced other species and treatment-specific responses.