Episodic Growth and Relative Shoot: Root Balance in Loblolly Pine Seedlings

Leaf, root and stem systems of loblolly pine seedlings are characterized by a seasonal periodicity in growth, during which they alternate in spurts of activity. Despite this periodicity, the allometric coefficient describing the ratio of the relative growth rates of leaf to root remains constant for at least the first two years of development. In part, constancy results from the inability of variation in the allocation of growth increment during brief periods to change a pre-existing structure accumulated over the life of the seedling. In addition, alternating periods of leaf, root and stem growth may represent the action of feedback mechanisms which operate to maintain an adaptive balance between organ systems.