Document: DOU-3-31-20

When branch autonomy fails: Size does matter.

SPRUGEL, D.G.*

University of Washington, Seattle, WA 98195-2100 USA ¹

Abstract:
Sprugel and Hinckley proposed that "One can predict many important growth and physiological characteristics of a branch from its morphology and position in the canopy alone, without reference to the characteristics of the tree as a whole". A variety of newer studies show that this is only partly true. For example, shoots attached to a shaded tree grow more rapidly than shoots in the same light environment but attached to a sunlit tree. Although counterintuitive, this is a logical allocation of resources within a tree: A branch in a more favorable environment than the rest of the branches on a tree will receive a larger proportion of the resources available to support growth, while one that is more shaded than others on its tree will receive a lower proportion of resources. This is consistent with the finding that shaded trees often invest more carbon and nitrogen per unit of light captured than trees that have access to better-lit environments. A related pattern occurs when one branch of a tree is exposed to a different pollution treatment than the rest of the tree: A "polluted" branch on a "polluted" tree photosynthesizes more rapidly than a "polluted" branch on a "clean" tree, and a "clean"branch on a "polluted" tree photosynthesizes more rapidly than a "clean" branch on a "clean" tree. These examples suggest important limitations to the branch autonomy hypothesis.

Keywords: branch autonomy; light; pollution

This abstract is being presented at: 10:15 AM in session:
Oral Session #1: Plant Carbon Allocation.