When containerized black spruce seedlings (Picea mariana Mill.) are grown rapidly, their stems can become deformed, i.e., they bend over, grow horizontally, and obtain a permanent crook. To determine what physiological differences exist between these stem-deformed and healthy seedlings, we fed labeled amino acid,14C-phenylalanine, a precursor of lignin and phenolics as well as a constituent of proteins, to both kinds of seedlings and followed the partitioning of this 14C after a chase period of 24, 48, and 72 h. For one group of seedlings, intact plants incorporated the l4C-phenylalanine through their root systems, whereas for a second group of plants, root systems were excised and the 14C-phenylalanine was incorporated directly by stems. When the 14C was incorporated by roots, stem-deformed seedlings partitioned more l4C to protein and less to lignin and phenolics. However, when the 14C was incorporated directly by stems, the differences between stem-deformed and healthy seedlings nearly disappeared. Furthermore, the distribution of 14C following root incorporation in stem-deformed seedlings was the same as that for stem incorporation in both types of seedlings. Thus, stem-deformed black spruce seedlings behave as if their root systems are not performing their normal role in metabolizing phenylalanine into lignin precursors. The ratio of 14C allocated to phenolic-containing compounds associated with growth to 14C allocated to those compounds associated with the differentiation of existing plant structures was 3.7 times higher in stem-deformed seedlings than in healthy ones. These results demonstrate that roots can play an important role in controlling the partitioning of carbon between growth and differentiation. Key words: black spruce, differentiation, lignification, phenolics, stem deformation, secondary metabolism.
Harvesting peatland black spruce: Impacts on advance growth and site disturbance
