Carbon dioxide enrichment and the role of carbohydrate reserves in root growth potential of cold-stored Engelmann spruce (Picea Engelmannii Parry) seedlings

Two experiments were conducted to examine the role of carbohydrate reserves in spring root growth potential (RGP)of Engelmann spruce (Picea engelmannii Parry) seedlings. In the first experiment, the effects of pre-storage carbon dioxide enrichment (CE) on total non-structural carbohydrates (TNC) and post-storage root growth were studied. Seedlings were grown from seed for 202 days in growth chambers with ambient (340 μL•L-1) and CO2 enriched(1000 μL•L-1) air. Reciprocal transfers between treatments took place at 60 and 120 days. Photoperiod was reduced at100 days to induce bud set. After 180 days seedlings were hardened-off for storage at -5°C. At 268 and 327 days, seedlings were planted in a growth chamber in three water baths. New roots >5 mm long were counted after 28 days growth. Seedlings were also assessed for bud break every two days. At each planting time, and at 80, 120, 140, and 202days, seedlings were randomly selected from each of the CO2 treatments and harvested for analysis of starch and soluble sugar content. Growth data were also collected. In the second experiment, the relative contributions of reserve carbon and current photosynthate to new root growth were studied. Seedlings were raised using standard nursery procedures up to bud set (end of September, 1990). Seedlings were then moved into a growth chamber and placed in four Plexiglas boxes for stable carbon isotope labelling. Two boxes received ambient CO2 with normal isotopic composition [More abstracts follows]Forestry, Faculty ofGraduat