EFFECT OF COBALT ON CHLOROPHYLL AND CAROTEOID CONTENTS IN TOMATO PLANTS.

The effect of increased concentrations of cobalt (Co) (0, 50, 100, and 200 mg kg⁻¹) and treatment with sewage sludge was investigated on the chlorophyllic pigments and carotenoids of tomato (Lycopersicon esculentum Mill cv. Ramy) plants, grown in a calcareous soil. Aerobically digested sewage sludge was applied at the rates of 2 and 4 g sewage sludge/100 g soil d.w., equivalent to 60 and 120 t ha⁻¹. Treatments were compared with a non-fertilized control. Six leaf samples were taken at 27, 41, 55, 73, 94, and 105 days for each treatment and chlorophyll content was determined. Five leaf samples were taken at 35, 62, 75, 89, and 106 days to determine carotenoids content. Organic fertilization enhanced the levels of chlorophyll and carotenoids in tomato leaves. Cobalt induced a significant decrease in all the pigments analyzed, correlated with the increased presence of cobalt in soil. Also the negative effect of this pollutant seem to be enhanced by fertilization, probably due to a higher availability of Co with the increasing application of sewage sludge. [ABSTRACT FROM AUTHOR]