Comparison of Various Analysis Methods for Determination of Iron Chlorosis in Apple Trees

The objective of this study was to compare iron (Fe) concentrations (mg kg −1 ) of the leaves measured by different methods and to determine the most suitable method to be used in evaluation of iron chlorosis in apple trees. For this purpose, green and chlorotic leaves were collected from 76 apple orchards in 1998 and 1999. Iron concentrations (mg kg −1 ) of dried leaf samples were measured with 4 different methods, 1 N HCl (Method 1), 0.1 N HCl (Method 2), 0.005 M DTPA (Method 3), and 1.5% o-phenanthroline (Method 4). Total Fe concentrations (mg kg −1 ) of dried leaf samples were also analyzed. Total chlorophyll and peroxidase enzyme activity in fresh leaf samples were measured. The total chlorophyll, peroxidase enzyme activity, Fe concentrations (mg kg −1 ) determined by Method 1, Method 3, Method 4, and total Fe concentrations (mg kg −1 ) of green leaves were higher than those of chlorotic leaves. On the other hand, no significant difference was found between Fe concentrations (mg kg −1 ) of green and chlorotic leaves, measured with Method 2. Significant relationship observed amongst chlorophyll concentrations, peroxidase enzyme activity, and Fe concentrations (mg kg −1 ) of samples suggests that 1 N HCl method was the most suitable method amongst the methods used in this study for apple trees.