Uptake of Co, Cs, Mn, Ni and Zn by Lemna minor and their effects on physiological and biochemical functions

Abstract

An investigation is presented of the uptake of Co, Cs, Mn, Ni and Zn and their effects on L. minor's growth, photosynthetic pigments, photosynthesis, starch and soluble sugars content. In general, the higher the initial exposure concentration, the lower the removal percentage and bioconcentration factor of the elements. An exponential function fitting was obtained when the total pollutant removal per L. minor dry matter is expressed as function of the initial pollutant concentrations. Based on the maximum removal values the following ordering was obtained: Mn > Cs > Zn > Co > Ni. The essential micronutrient Mn and the non-essential element Cs were highly accumulated. Cs shows major similarities to the essential element K, since both elements are taken up through the same transport channels as K. Both Co and Ni have lower EC50 values resulting in a high toxicity, which can be connected with the low removal rate of these elements. Growth and photosynthetic pigments significantly decreased and starch content significantly increased as a function of the concentration. The photosynthetic capacity of L. minor was the most negatively affected by Zn and was enhanced during Mn exposure.