COPPER NUTRITION OF EUCALYPTUS-MACULATA HOOK SEEDLINGS - REQUIREMENTS FOR GROWTH, DISTRIBUTION OF COPPER AND THE DIAGNOSIS OF COPPER DEFICIENCY

A glasshouse experiment was conducted to define the response of Eucalyptus maculata seedlings to the addition of nine rates of copper (Cu) to a Cu-deficient sand. Plants were harvested 128 days from sowing. Symptoms of Cu deficiency included marginal necrosis in young fully expanded leaves (YFEL), deformed leaf margins, death of lateral shoots, bleeding at nodes on the main stem and reduced lignification of xylem fibres and vessels. Plant height and the number of nodes on the main stem were unaffected. In plants supplied with 0 Cu, whole top and root fresh weights were depressed by 27% and 32% respectively. The external Cu requirement for maximum growth of E. maculata seedlings was similar to that for wheat grown in the same soil. In Cu-adequate plants, leaf Cu concentrations decreased with distance from the shoot apex. Cu levels in stems varied little with position and were similar to the YFEL. Cu concentrations in leaves and stems were depressed in Cu-deficient plants to <1.0 mu g g(-1) dry weight (d.w.) (roots: 1.5 mu g g(-1) d.w.). The external Cu supply did not greatly alter the distribution of Cu within the plant. Young leaves at the shoot tip are recommended for diagnosis of Cu deficiency: critical values for shoot d.w. were about 1.5 mu g Cu g(-1) d.w. Lignification of wood was suppressed where Cu concentrations fell below 1.5 mu g g(-1) d.w.: the Bussler test for lignification would thus be a valuable indicator of Cu deficiency.