BAR‐AKIVA, A., Division of Citriculture, Volcani Institute of Agricultural Research, Bet Dagan, Israel
SAGIV, J., Division of Citriculture, Volcani Institute of Agricultural Research, Bet Dagan, Israel
HASDAI, D., Division of Citriculture, Volcani Institute of Agricultural Research, Bet Dagan, Israel

Ca and S deficiencies cause a strong, N, P and Mg deficiencies a slight, and K deficiency an intermediate decrease in the aldolase activity of Eureka lemon leaves. Fe and Zn deficiencies result in a moderate decrease in the activity. Cysteine increases the enzyme activity (approximately 30 %). Opposed to with yeast aldolase, EDTA inhibits the enzyme activity only moderately in control (full nutrient) lemon leaves nor does Zn EDTA restore it. Gel electrophoresis of yeast and lemon leaves' aldolase isoenzymes also exhibited different patterns. Dialysis studies and other reactivation experiments with different ions failed to establish specific metal requirements of the aldolase in the lemon leaves. However, infiltration of Zn into Zn‐deficient detached and intact citrus leaves brought about a partial restoration of the enzyme activity. In view of these results, the relationship between the citrus leaf enzyme and the varying types of aldolase enzymes is discussed. Copyright © 1971, Wiley Blackwell. All rights reserved