Abstract:
The aim of this study was to determine the response of Lemna minor L. to 6, 16, and 60 mg.L-1 phosphate concentrations, which are resembled in hypertrophic lake types, for 24, 48, 96, and 144 hours in laboratory conditions. Glutathione reductase (GR; EC 1.8.1.7) and catalase (CAT; EC 1.11.1.6) activities, thiobarbituric acid reactive substances (TBARS), total protein, chlorophyll a and b, carotenoids, and total phenolics contents in L. minor were determined spectrophotometrically in different phosphate concentrations at different time intervals. GR showed the maximum decrease at the minimum phosphate concentration at 24(th) hour. CAT also decreased at 24(th), 48(th), and 96(th) hours, especially at high phosphate levels. TBARS decreased at 6 mg.L-1 and 60 mg.L-1 phosphate concentrations at 144(th) and 24(th) hours, respectively. Total protein content decreased at 96(th) and 144(th) hours, especially at the highest phosphate concentration. Chlorophyll a decreased at 48(th) and 144(th) hours especially at the highest phosphate level, whereas chlorophyll b content increased at 48(th) and 96(th) hours at the same concentrations. The contents of phenolics and carotenoids were not affected except for a decrease in carotenoids at 48(th) hour. As a result, phosphate at its hypertrophic levels lead to pronounced effects in L. minor.
