Influence of some metal chelators and light regimes on bioaccumulation and toxicity of Cd²⁺ in duckweed (Lemna gibba)

Abstract

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.

Combined effects of cadmium and linear alkyl benzene sulfonate on Lemna minor L.

“…The initial uptake of Cd by L. minor is in agreement with the data of Polar and Kucukcezzar (1986). Simultaneous exposure to Cd and LAS reduced DNA, RNA, protein and phospholipid synthesis compared with individual exposures.…”

The Effect of EDTA on Maize Seedlings Response to Cd-Induced Stress

“…1). Polar and Kü<;ükcezzar (1986) however concluded from their observations that the detoxificating effect of ED TA cannot be al ways interpreted in this way.…”

“…Decrease of cad mium toxicity by ED TA was described by Polar and Kü^ükcezzar (1986) for relative growth rates of duckweed and also by Greger andLindberg (1986 and1987) in the case of sugar content and growth of sugar beet. In the latter case toxicity symptoms depended on Cd and ED TA concentra tion in the nutrient medium.…”

Changes in uptake of calcium caused by phytotoxicity of cadmium in Salvinia molesta

“…This is in agreement with the reported enhanced uptake of cations during illumination (McLean andWilliamson 1977, Weigel andJager 1980) and the continued translocation to the leaves in the dark period. Polar and Kucukcezzar (1986) reported that light duration alone or in combination with metal chelators affects the uptake of iroq, manganese, zinc and cadmium. Our results also revealed that in Cd-treated plants I Fe, Mn and Zn were generally higher as compared to controls (data not reported).…”