Carbon Metabolism in Scions of Colorado Blue Spruce: II. Carbon Storage Compounds

The study evaluated the roles of storage carbohydrates and neutral lipids in the success of Colorado blue spruce ( Picea pungens Englemann ‘Hoopsi’) grafts. These scions do not require photosynthesis nor receive photosynthates from the rootstock during union development. Carbohydrate and neutral lipid contents, along with respiration and scion water relations, were measured during union development. Stored carbon compounds were sufficient to supply the needs of the scion during the 9 weeks of union development. Estimates of carbohydrate use indicated that decreases in sugar content (bark and needle) were insufficient to account for more than 25% of the estimated respiration. The results indicate that the quantity of carbon storage compounds is not a factor in graft success. We propose that neutral lipids may be the major carbon reserve of the scion during graft formation.