Stem girdling manipulates leaf sugar concentrations and anthocyanin expression in sugar maple trees during autumn
P. F. Murakami (1, 2), P. G. Schaberg (1) and J. B. Shane (3)
1. Forest Service, U.S. Department of Agriculture, Northern Research Station, 705 Spear Street, South Burlington, VT 05403, USA / 2. Corresponding author () / 3. The University of Vermont, Rubenstein School of Environment and Natural Resources, 81 Carrigan Drive, Burlington, VT 05405,
USA / Received January 18, 2008; accepted June 3, 2008; published online August 1, 2008
Summary
To better understand the effects of sugar accumulation on red color development of foliage during autumn, we compared carbohydrate
concentration, anthocyanin expression and xylem pressure potential of foliage on girdled versus non-girled (control) branches
of 12 mature, open-grown sugar maple (Acer saccharum Marsh.) trees. Half of the study trees were known to exhibit mostly yellow foliar coloration and half historically displayed
red coloration. Leaves from both girdled and control branches were harvested at peak color expression (i.e., little or no
chlorophyll present). Disruption of phloem export by girdling increased foliar sucrose, glucose and fructose concentrations
regardless of historical tree color patterns. Branch girdling also increased foliar anthocyanin expression from 50.4 to 66.7%
in historically red trees and from 11.7 to 54.2% in historically yellow trees, the latter representing about a fivefold increase
compared with control branches. Correlation analyses indicated a strong and consistent relationship between foliar red coloration
and sugar concentrations, particularly glucose and fructose, in both girdled and control branches. Measures of xylem pressure
potentials confirmed that girdling was a phloem-specific treatment and had no effect on water transport to distal leaves.
Results indicate that stem girdling increased foliar sugar concentrations and enhanced anthocyanin expression during autumn
in sugar maple foliage. Native environmental stresses (e.g., low autumn temperatures) that reduce phloem transport may promote
similar physiological outcomes.
