Arboriculture & Urban Forestry 32(6): November 2006 281 Table 3. (experiment 2) Sucrose-enhanced recovery of leaf PI, necrosis, and chlorophyll content of containerized English oak (Quercus robur L.) placed outdoors with time (weeks) based on quadratic regression analysis after application of salt (NaCl). Treatment 30 g NaCl 60 g NaCl PI Regression: y a+bT+cT2 y −3.98 + 3.29T – 0.28T2 y −4.75 + 2.82T – 0.23T2 Sucrose 25 g + 30 g NaCl y −10.94 + 6.23T – 0.48T2 Sucrose 25 g + 60 g NaCl y −6.58 + 3.95T – 0.31T2 Sucrose 50 g + 30 g NaCl y −6.41 + 3.45T – 0.28T2 Sucrose 50 g + 60 g NaCl y −5.90 + 3.03T – 0.24T2 r2 Leaf necrosis Regression: y a+bT+cT2 0.93 y 4.98 to 0.15T – 0.02T2 0.94 y 5.36 to 0.11T – 0.03T2 0.90 y 5.71 to 0.31T – 0.02T2 0.97 y 5.18 to 0.29T – 0.03T2 0.95 y 4.43 + 0.26T – 0.67T2 0.94 y 5.59 to 0.23T – 0.02T2 r2 Chlorophyll content Regression: y a+bT+cT2 0.99 y 8.01 + 0.35T + 0.08T2 0.94 y 7.27 + 0.60T + 0.05T2 0.97 y 11.11 to 2.57T + 0.62T2 0.91 y 8.86 to 1.19T + 0.41T2 0.99 y 13.42 to 4.01T + 0.71T2 0.98 y 9.33 to 1.68T + 0.50T2 r2 0.98 0.86 0.90 0.98 0.93 0.97 y, leaf PI, necrosis, and chlorophyll content value; a, leaf PI, necrosis and chlorophyll content of control value (calculated intercept); b, rate of PI, necrosis, and chlorophyll content with time (T), c,rate of change. PI and chlorophyll values mean of six trees, five leaves per tree, leaf necrosis values mean of six trees. of the experiment at week 8 (Tables 3 and 4). Irrespective of species, sucrose-treated trees were the most capable of recov- ery as reflected by higher regression values with respect to PI and leaf chlorophyll recovery and lower regression values with respect to leaf necrosis (Tables 3 and 4). Such responses in sucrose-treated trees are associated with enhanced recov- ery of leaf photosynthetic integrity, improved photosynthetic efficiency, and reduced degradation of the chlorophyll mol- ecule structure compared with nonsucrose-treated trees. Re- covery rates of salt-damaged trees treated with sucrose ranged from 5% to 50% higher than nonsucrose-treated trees (Tables 3 and 4). In all cases, nonsucrose-treated trees had the least capacity for recovery. Regardless of tree species, maxi- mal recovery rates were recorded in trees treated with sucrose at 25 g (0.9 oz) rather than 50 g (1.8 oz) after salt treatment at 30 (1.1) and 60 g (2.1 oz) per liter of water. None of the treatments used in this investigation altered the ratio of chlo- rophyll a:b in English oak (3.09 to 3.24) or holly (3.29 to 3.44; data not shown). Eight weeks after sucrose application, leaf area, root, leaf, shoot, and total plant dry weight were consistently higher (20% to 50%) in sucrose-treated trees irrespective of species with one exception: English oak treated with 50 g (1.8 oz) sucrose after application of salt at 60 g (2.1 oz) per liter of water in which values were compa- rable with salt-only-treated English oak (Tables 5 and 6). Regardless of tree species, maximal growth responses were recorded in trees treated with sucrose at 25 g (0.9) rather than 50 g (1.8 oz) after salt treatments (Tables 5 and 6). DISCUSSION There is a growing body of evidence that application of car- bohydrates, particularly sucrose, can provide useful protec- Table 4. (experiment 2) Sucrose-enhanced recovery of leaf PI, necrosis, and chlorophyll content of containerized holly (Ilex aquifolium L.) placed outdoors with time (weeks) based on quadratic regression analysis after application of salt (NaCl). Treatment 30 g NaCl 60 g NaCl PI Regression: y a+bT+cT2 y 1.98 + 1.30T – 0.18T2 y 2.39 + 0.96T – 0.10T2 Sucrose 25 g + 30 g NaCl y −2.36 + 3.73T – 0.32T2 Sucrose 25 g + 60 g NaCl y 0.315 + 2.05T – 0.19T2 Sucrose 50 g + 30 g NaCl y 1.45 + 1.41T – 0.12T2 Sucrose 50 g + 60 g NaCl y 0.89 + 1.90T – 0.17T2 r2 Leaf necrosis Regression: y a+bT+cT2 0.42 y 4.50 to 0.11T – 0.01T2 0.84 y 4.56 to 0.12T – 0.02T2 0.91 y 4.36 to 0.16T – 0.01T2 0.90 y 4.20 to 0.03T – 0.02T2 0.88 y 3.37 + 0.09T – 0.03T2 0.96 y 4.24 to 0.10T – 0.02T2 r2 Chlorophyll Content Regression: y a+bT+cT2 0.95 y −2.51 + 8.82T – 0.53T2 0.98 y −4.10 + 8.60T – 0.40T2 0.94 y −15.15 + 16.75T – 1.08T2 0.95 y 4.70 to 3.91T + 0.15T2 0.96 y −9.96 + 13.49T – 0.81T2 0.98 y −7.40 + 11.67T – 0.66T2 r2 0.93 0.88 0.94 0.96 0.90 0.88 y, leaf PI, necrosis, and chlorophyll content value; a, leaf PI, necrosis and chlorophyll content of control value (calculated intercept); b, rate of PI, necrosis, and chlorophyll content with time (T), c,rate of change. PI and chlorophyll values mean of six trees, five leaves per tree, leaf necrosis values mean of six trees. ©2006 International Society of Arboriculture
November 2006
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