EFFECT OF ENVIRONMENTAL POLLUTION WITH TETRACYCLINE AND CADMIUM ON CHLOROPHYLL CONTENT IN SPINACH (SPINACIA OLERACEA L.) LEAVES SUBJECTED TO COLD STORAGE

This paper analysed chlorophyll degradation in spinach leaves from plants affected by cadmium and tetracycline soil contamination, stored for 32 weeks at t= -18 degrees C. The first-order reaction kinetics were determined for chlorophyll degradation. In plants growing on soil containing tetracycline and cadmium, two ranges of chlorophyll degradation occur: 1 - a slow degradation, during storage for up to 20 weeks, occurring at constant degradation rate, k = 0.00594 +/- 0.00029 week(-1) for tetracycline and k = 0.00761 +/- 0.00026 week(-1) for cadmium, and 2 - a fast degradation, occurring later, with constant k = 0.04484 +/- 0.00137 week(-1) and k = 0.06777 +/- 0.00171 week(-1) for tetracycline and cadmium, respectively. Those two ranges were not observed for spinach growing without contamination (k = 0.00679 +/- 0.00027 week(-1)). Chlorophyll degradation occurred eight times faster for tetracycline and ten times faster for cadmium. After 32 weeks of storage 19.4% and 13.6% of chlorophyll were left in small leaves affected by tetracycline and cadmium, respectively. In spinach leaves of harvesting maturity (50-days-old, large leaves), lower values of rate constants were found for range 2, amounting for dose (90 mg/kg soil) to k = 0.02945 +/- 0.00151 week(-1) (for tetracycline) and k = 0.03511 +/- 0.00124 week(-1) (for cadmium) and 50% chlorophyll was left after 32 weeks. Chlorophyll degradation degree depends on soil contamination, leaf size and time of exposure to contaminants.