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A factorial culture experiment was designed to investigate the influence of light regimes and of some metal chelators on the accumulation of cadmium by Lemna gibba L. The plants were grown in a complete nutrient solution containing Cd2+ concentrations ranging from 0 to 27 μM with or without EDTA, ethylenediamine‐N,N′‐bis‐(o‐hydroxyphenylacetic acid) (EDDHA) or salicylic acid. Each experiment was run for eight days in 18 h:6 h light:dark or continuous light. An increase in the Cd2+ concentration in plants and a simultaneous drop in accumulation efficiency (ratio of Cd2+ concentration in plants to the initial Cd2+ concentration in the nutrient solution) with increasing ambient Cd2+ levels was best represented by regression power curves. At the lowest Cd2+ concentration which caused a significant decrease in the relative growth rate of duckweed, there was a decrease in manganese and zinc and an increase in the iron level in the plants. EDDHA and EDTA protected in some cases against the toxic action of cadmium without preventing its uptake by plants. It was thus observed that 9 μM or higher levels of Cd2+ were toxic to Lemna gibba depending on the chelator and light regime. Duckweed grown in continuous light produced, in general, more dry matter and hence accumulated more cadmium.

Contamination levels and variation of 137Cs in tea plant leaves from 1986-1992 were determined over the coast line of the Eastern Black Sea region in Turkey. The decrease of 137Cs radionuclide concentration in tea plant leaves may be described by a double exponential function with 94.8% activity lost with a Teff of 125 d and 5.2% activity lost with a Teff of 1,114 d.

Lichen samples collected before and after the Chernobyl accident were analysed for radiocesium activity. I37 Cs activity was detected in some samples collected before Chernobyl. 134 Cs and 137 Cs were detected in all the samples after the accident. The levels of the total cesium activity counted in the samples proved that the eastern region of the Black Sea was affected by Chernobyl at a very high degree compared with other parts of Turkey.

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