COPPER DEFICIENCY AND TOXICITY IN 2 TROPICAL LEAF VEGETABLES (CELOSIA-ARGENTEA L AND AMARANTHUS-DUBIUS MART EX THELL)

Seeds of C. argentea and A. dubius were sown in sand culture laced with Cu concentrations of 0, 1, 2, 4, 8 and 16 mg/l and harvested at 48 days after emergence. Plants (3- to 4-wk old) grown in 0 mg/l Cu showed symptoms of Cu deficiency. Most of the young leaves were chlorotic and cupped upwards. Healthy plants were observed in the 1 and 2 mg/l treatments but plants grown in 4, 8 and 16 mg/l Cu were also chlorotic. The degree of chlorosis increased with increasing Cu concentration. Chlorotic symptoms due to deficiency as well as toxicity spread from the top towards the bases of leaves. At harvest except for the 2 mg/l regime where growth was vigorous, chlorosis was present in all treatments. Mature leaves of plants grown in 4, 8 and 16 mg/l Cu treatments senesced by the 35th day, whereas those of 0 and 1 mg/l Cu plants did not. Plants in the 0 mg/l (deficiency) and 8 and 16 mg/l treatments (toxic) had stunted growth, reduced leaf area, reduced dry matter production and reduced total chlorophyll content. Leaf ascorbic acid, P and Fe concentrations were significantly depressed with increase in leaf Cu. Leaf N concentrations increased with increase in leaf Cu. The relationships between leaf Cu and some components of growth, leaf mineral composition were also examined.