Effects of cadmium stress on growth, metal accumulation and organic acids of <i>Spartina alterniflora</i> Loisel.

Abstract

A study quantifying the effects of exogenous cadmium (Cd) on growth, Cd bioaccumulation and organic acids of Spartina alterniflora was conducted. The experiment consisted of three levels of exogenous Cd²⁺ concentrations: 0, 50, and 200 mg/kg. Total Cd and water-soluble Cd were determined. Plant height, tiller number, spike number, electrolyte leakage rate (ELR), free proline, malondialdehyde (MDA), soluble sugar and organic acids were also measured. The results showed that plant height, tiller number and spike number reduced with increasing Cd²⁺ concentration. However, ELR, free proline, MDA, and soluble sugar were all promoted under Cd stress. Cd accumulated in inflorescences, leaves, stems, rhizomes and fine roots, and increased greatly with increasing Cd2+ concentration. Exogenous Cd²⁺ significantly reduced the growth of inflorescences, leaves, stems and rhizomes, with Cd accumulations not more than 15.68 μg/g dry weight (DW), respectively. However, biomass of fine roots did not reduce significantly with increasing Cd²⁺ concentration. Furthermore, Cd accumulation in fine roots reached to 390 μg/g DW under the treatment Cd200. Oxalic and citric acids were the two most abundant organic acids in S. alterniflora. Contents of oxalic acid in inflorescences, stems and fine roots were all positively related with Cd bioaccumulations indicating that oxalic acid might be related with Cd sequestration in fine roots and Cd transportation from underground to aboveground parts of S. alterniflora. Contents of citric acid in fine roots and ascorbic acid in rhizomes increased with increasing exogenous Cd²⁺ concentration, suggesting that accumulation of citric acids in fine roots and ascorbic acid in rhizomes of S. alterniflora might also be related to its Cd bioaccumulation and detoxification.

Key words: Spartina alterniflora, cadmium pollution, growth, organic acid, phytoremediation.