CARBOHYDRATE RESERVE ACCUMULATION AND DEPLETION IN ENGELMANN SPRUCE (PICEA-ENGELMANNII PARRY) - EFFECTS OF COLD-STORAGE AND PRESTORAGE CO2 ENRICHMENT

The effects of pre-storage CO2 enrichment on growth, non-structural ca rbohydrates and post-storage root growth potential of Engelmann spruce (Picea engelmannii Parry) seedlings were studied. Seedlings were grow n from seed for 202 days in growth chambers with ambient (340 mu l l(- 1)) or CO(2)ched (1000 mu l l(-1)) air. Some seedlings were transferre d between CO2 treatments at 60 and 120 days. Photoperiod was reduced a t 100 days to induce bud set and temperature was reduced at 180 days t o promote frost hardiness development for storage at -5 degrees C for 2 or 4 months. Stored seedlings were planted in a growth chamber after thawing for one week at +5 degrees C. At 80, 120, 140 and 202 days, a nd at each planting time after storage, seedlings were harvested for g rowth measurements and analysis of starch and soluble sugar concentrat ions. Planted seedlings were assessed for bud break every two days and new roots > 5 mm long were counted after four weeks. Carbon dioxide e nrichment increased root collar diameter and almost doubled seedling b iomass, with the most obvious effects occurring after bud set. Stem he ight was affected only slightly and shoot/root ratios were not affecte d at all. Carbon dioxide enrichment increased the rate of reserve carb ohydrate accumulation, but did not influence the final concentration a ttained before storage (accounting for 32% of seedling dry weight). Ne edles were the major storage organ for soluble sugars, whereas roots w ere the major storage organ for starch. Soluble sugars were not strong ly affected by two or four months of storage, but starch was reduced b y more than 50% in all plant parts. None of the CO2 treatments had an impact on bud break or root growth potential.