Plantand Soil 167: 181-187, 1994. (~) 1994 KluwerAcademicPublishers.Printed in the Netherlands. Copper nutrition of Eucalyptus maculata Hook. seedlings: Requirements for growth, distribution of copper and the diagnosis of copper deficiency B. Dell School of Biological Sciences, Murdoch University, Perth 6150, Western Australia Received9 February1994. Accepted in revisedform22 July 1994 Key words: copper deficiency, critical concentrations, diagnosis, Eucalyptus maculata, lignification, symptoms Abstract 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/~g g-Z dry weight (d.w.) (roots: 1.5 #g g-l 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 #g Cu g-1 d.w. Lignification of wood was suppressed where Cu concentrations fell below 1.5 /lg g-l d.w.: the Bussler test for lignification would thus be a valuable indicator of Cu deficiency. Introduction Disorders due to nutrient imbalances in eucalypt plan- tations have been widely reported (Dell and Malajczuk, 1994; Will, 1961). In particular, where fertilizer prac- tices involve the addition of macronutrients such as N and P in forms which are low in trace elements, sec- ondary micro-element deficiencies can be induced. In southwestern Australia for example, Cu deficiency has been identified as the cause of distorted growth in 2-3 year old stands of Eucalyptus maculata fertilized with mono-ammonium phosphate at planting on a disturbed laterite profile (Dell and Bywaters, 1989). The only previous record of Cu deficiency in eucalypts is on seedlings of E. tereticornis grown in nutrient solution (Malavolta et al., 1962). A diagnostic procedure for Cu deficiency in euca- lypts would assist in the management of forest nurs- eries as well as for established plantations on copper- deficient soils. Some of the advanced symptoms of cop- per deficiency in plantations (Dell and Bywaters, 1989; Dell and Robinson, 1993) can be confused with the boron disorders described by Savory (1962) and Dell and Malajczuk (1994). For agricultural species, soil analysis does not always discriminate between respon- sive and non-responsive sites (Robson and Reuter, 1981). Copper concentrations in parts of the shoot have proved to be sensitive predictors of the copper status of many agricultural species (Robson and Reuter, 1981). A glasshouse experiment was undertaken to describe relationships between copper supply and growth of Eucalyptus maculata seedlings, and to define critical concentrations of copper in selected tissues. Wheat was grown for comparison since the copper nutrition of this species (Robson et al., 1984) has been explored in depth on the soil chosen for this experi- ment.