Use of Sugars to Improve Root Growth and Increase Transplant Success of Birch (Betula Pendula Roth.)
Glynn C. Percival and Gillian A. Fraser
Abstract: Two field trials undertaken in 1999 and 2003 investigated the influence of a range of sugars applied as a root drench at 25, 50, and 70 g/L (3.4, 6.8, and 10.3 oz/gal) of water on root and shoot growth, chlorophyll fluorescence, photosynthetic rates, and leaf carotenoid and chlorophyll concentrations of birch (Betula pendula Roth.). Irrespective of concentration and year, the sugars galactose and rhamnose had no significant effects on tree growth or leaf photosynthetic properties. Application of the sugar maltose increased shoot and root dry weight in the 1999 trial but had no effect in the 2003 trial. Sucrose, fructose, and glucose increased shoot and root dry weight in both 1999 and 2003 trials; however, growth responses were influenced by the concentration of sugar applied. In many cases, sugar application increased the number of new roots formed by week 6 but had no significant effects on the length of existing roots or shoot growth. By week 24, increases in both root and shoot growth were recorded. Sugar feeding at 25 g/L (3.4 oz/gal) of water had no significant effect on leaf chlorophyll fluorescence, photosynthetic rates, or carotenoid and chlorophyll concentrations; however, sugar feeding at 50 and 75 g/L (6.8 and 10.3 oz/gal) of water reduced these values by week 6. At the cessation of the experiment, maximal increase in root and shoot growth was associated with a root drench of sucrose at a concentration of 70 g/L (10.3 oz/gal) of water in both 1999 and 2003 trials. Lower mortality rates recorded in sugar-treated trees indicate applications of sugars would aid in the survival of young birch trees following transplanting.
Keywords: Carbohydrates; resource allocation; gene
expression; transplant shock; chlorophyll fluorescence;
photosynthesis; chlorophyll; carotenoid; plant vitality