68 Percival and Fraser: Sugars to Improve Root Growth and Transplant Success airflow was 1 mL/s/cm2 leaf area. Calculation of the photo- synthetic rates was carried out according to von Caemmerer and Farquhar (1981). Readings were taken at weeks 6 and 24. Two leaves per tree were selected for measurements. Leaves were tagged to ensure that assessments were taken from the same leaf throughout the experiment. Leaf Chlorophyll and Carotenoid Analysis Chlorophyll and carotenoids were extracted from three leaf samples per tree at weeks 6 and 24 after transplanting by suspending 1 g (0.04 oz) of fresh tissue in 5 mL (0.2 oz) of 80% v/v aqueous acetone. After centrifugation in closed vials, an aliquot of the supernatant was transferred to a 1 cm (0.4 in.) path glass cuvette. Chlorophylls a and b and total carotenoid concentration were calculated according to the equations of Lichtenthaler (1987) following measure- ment of absorbance at 663, 645, and 480 nm in a spectro- photometer (PU8800 Pye Unicam, Portsmouth, UK). Plant Dry Weights and Leaf Area At weeks 6 and 24 after budbreak, five trees per treatment were destructively harvested and leaf, shoot, and root dry weight recorded after oven drying at 85°C (185°F) for 48 h. Girth increments were quantified using Mantax blue precision calipers (Haglöf Sweden AB, Langsele, Sweden) from measurements taken 7.5 cm (3 in.) above the substrate surface. In all cases, root systems were excavated gently by hand and using a spade. Soil was removed by washing with water through a 4 mm (0.16 in.) screen. Root growth potential (number of new white roots formed >1 cm [0.4 in]) and root length (the straight-line distance from the trunk to the furthest root tip) were measured. Statistical Analysis Effects of sugars on growth, chlorophyll fluorescence, photosynthetic rates, chlorophyll and carotenoid concen- trations, and significant interactions between sugar and concentration were determined by two- and one-way analyses of variance (ANOVA) following checks for normal- ity and equal variance distributions. Differences between treatment means were separated by the least significance difference (LSD) at the 95% confidence level (P > 0.05) using the Genstat V program. RESULTS There was no significant interaction between sugar type and concentration for any parameter in either the 1999 or 2003 trials (Table 1*). Sugar concentration affected only leaf dry weight in 2003. Sugar type affected chlorophyll and carotenoid content and Fv/Fm ratio in 1999 and root dry weight and Fv/Fm ratio in 2003. *Tables for this article appear on pp. 73–77. ©2005 International Society of Arboriculture No significant effects on growth or leaf photosynthetic properties were recorded following application of galactose, rhamnose, and maltose (2003 trial only), irrespective of concentration applied. For reasons of clarity, nonsignificant data are not shown. Chlorophyll Fluorescence, Photosynthesis, and Chlorophyll and Carotenoid Concentrations and Mortality No significant effects on Fv/Fm, Pn, or leaf chlorophyll and carotenoid concentrations were recorded following application of any of the sugars tested at a concentration of 25 g/L (3.4 oz/gal), with one exception: significantly reduced leaf carotenoid concentrations were found in trees supple- mented with fructose at week 6 in the 2003 trial. At week 6 in both the 1999 and 2003 trials, leaf chlorophyll and carotenoid concentrations and Pn and Fv/Fm were signifi- cantly lower (P < 0.05) in trees supplemented with sucrose, glucose, fructose, and maltose (1999 trial) at concentrations of 50 and 70 g/L (6.8 and 10.3 oz/gal ) compared with control values (Tables 2 and 3). Exceptions to this include, in the 1999 trial, fructose (leaf chlorophyll, carotenoid concentrations and Fv/Fm values) and maltose (Pn) applied at 50 g/L (6.8 oz/gal), where no significant effects were recorded. In the 2003 trial, no significant effects on Fv/Fm were found following application of 50 g/L (6.8 oz/gal) of sucrose, fructose, and glucose; on Fv/Fm following applica- tion of 70 g/L (10.3 oz/gal) of glucose; on leaf chlorophyll concentration following application of 50 g/L (6.8 oz/gal) of fructose; or on Pn following application of 70 g/L (10.3 oz/ gal) of glucose. In both 1999 and 2003 trials, no significant effects on Fv/Fm or Pn, or on leaf chlorophyll and carotenoid concen- trations were recorded at week 24. Results indicate a reduction in leaf photosynthetic properties by week 6 following application of sucrose, glucose, and fructose at 50 and 70 g/L (6.8 and 10.3 oz/gal). By week 24, a rising chlorophyll and carotenoid content and subsequent increase in Fv/Fm were mirrored by increased leaf photo- synthetic rates (Pn). No significant effects on the ratio of chlorophyll a:b (65:35) compared to controls were recorded (data not shown). Plant Growth Applications of sucrose, glucose, and fructose induced similar alterations in growth of birch in both 1999 and 2003 experiments (Tables 4 and 5). Irrespective of sugar type and concentration, no significant effects on root length, girth, or leaf and shoot dry weight were recorded at week 6. How- ever, a significant increase (P < 0.05) in root growth poten- tial and root dry weight was recorded following applications of sucrose, glucose, fructose, and maltose (1999 trial) at all
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