Subcellular distribution and chemical forms of lead in the red algae, Porphyra yezoensis

The subcellular distribution and chemical forms of lead (Pb) were examined in the red algae, Porphyra yezoensis. The algae was exposed to three different Pb treatments (0.01, 0.1 and 1.0 mg L^-1) for up to 144 h. In the control groups, about 45% of Pb was localized in the cell wall, and 27.5% in the organelle and soluble fractions respectively. The dominant chemical forms of Pb was extracted by 80% ethanol (52.9%), while the form extracted by NaCl (1 M) was lowest. In the treatment groups, the cell wall and the organelle fraction were the main subcellular fractions for the 0.10 mg L^-1 and 1.0 mg L^-1 groups; while for the 0.01 mg L^-1 groups, Pb was approximately distributed in the cell wall, organelle and the soluble fractions. The dominant ethanol extractable form of Pb in the control and 0.01 mg L^-1 groups were replaced by less active 2% acetic acid (HAc) extractable form in the 0.1 and 1.0 mg L^-1 groups. Different from other terrestrial plants, the proportion of 1 M NaCl extractable form of the pectates and protein integrated Pb in P. yezoensis was lowest for both control and treatment groups. The strategy with deposition Pb in the cell wall and formation the precipitation of less active HAc extractable form maybe one of the mechanisms for accumulation, transportation and detoxification of Pb in P. yezoensis.