EFFECTS OF ALUMINUM ON COPPER TOXICITY, AS REVEALED BY SOLUTION-CULTURE AND SPECTROGRAPHIC STUDIES OF CITRUS

Abstract

An apparently stimulating effect of aluminum on citrus growth is due to the antagonistic effect of aluminum on copper. In the absence of aluminum, 0.1 ppm copper was decidedly toxic to Valencia orange cuttings and to lemon cuttings. The addition of 0.1 ppm aluminum to cultures injured by such a concentration of copper was sufficient to offset this toxicity. The addition of 0.1 ppm aluminum to purified nutrient solutions containing only a trace of copper and other micronutrients slightly depressed plant growth. Under these conditions aluminum may have made it difficult for the plants to obtain enough copper or, perhaps other elements, for normal development. The addition of 2.5 to 5 ppm aluminum to purified base nutrient solutions greatly stimulated root development but depressed top growth. The detoxifying influence of aluminum on copper is seated in the roots. Aluminum does not prevent the absorption of copper by the roots but does, in some manner, prevent injury by this element. 9 references, 5 figures, 2 tables.