Apical Control of Diameter Growth in White Pine Branches
Young white pine (Pinus strobus L.) trees were girdled at the top or bottom of stem internodes. Girdles either above or just below a whorl of branches caused (1) diameter increase at the base of the branches, (2) decreased stem growth in the internode below the whorl of branches. Ring width was greatest on the underside of branches when the girdle was above, but ring width was evenly distributed on all sides of the branches when the girdle was below. A girdle at the top of an internode stopped growth in that internode. A girdle at the bottom of an internode had no effect on, or increased, growth in that internode. Each girdle reduced stem volume growth more than it increased branch volume growth. Branch diameter growth appears to be regulated by competition between stem and branch sinks for branch-produced photosynthate. Forest Sci. 27:95-101.
No Supplementary Data
No Article Media