Effect of cadmium on nutrients concentration in duckweed: a case of Lemna minor and Lemna gibba

Abstract

Pollution due to heavy metals in the aquatic environment remains a widespread concern. Heavy metal like cadmium (Cd) is associated with reduced absorption of nutrients, decreased cell growth, chlorosis, and necrosis of roots. In the present study, the effects of varied Cd concentrations on the macro and micronutrients (zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), potassium (K), calcium (Ca), and sodium (Na)) of duckweed plant species namely Lemna minor and Lemna gibba were investigated. Plant nutrients like Zn, Cu, Mn, and Fe were increased to 1460 mg/kg, 40 mg/kg, 1276 mg/kg, and 98.3 mg/kg respectively, for L. minor when compared with control and 1621.7 mg/kg, 28.3 mg/kg, 1081.7 mg/kg and 63.3 mg/kg respectively, in case of L. gibba with the increase in treatment time when treated with Cd. Na and K concentrations were found to be decreased with increasing metal concentration and treatment period. Statistical analysis (two-way ANOVA) also confirms the individual effect of metal concentration and treatment interval as well as a combined effect of both factors together on macro and micronutrient concentrations. The effect of Cd stress conditions on the various characteristic functional groups was also assessed with the help of Fourier-transform infrared spectroscopy (FTIR). FTIR spectra of both control and metal treated plants exhibited minor changes after the phytoremediation process. The study showed that the contents of essential macro and micronutrients (Zn, Cu, Mn, and Fe) were not significantly reduced by Cd even at a high concentration in the cultivation medium.