Characterization of Lead in the Tissues of Heavy Metal Tolerant Plant, Athyrium Yokoscen se (Fr. et Say. ) Christ

Abstract

The distribution and chemical form of lead in vegetative organs of Athyrium yokoscense (Fr. et Say. ) growing in the polluted areas resulting from lead tiles of the ruins of Kanazawa Castle, now on the campus of Kanawaza University have been investigated. The content of lead (by dry weight) in tissues of this fern species increases in the order of spores (-81 ppm) <sporangium (-740 ppm) <leaf blade (-2080 ppm) >petiol (-1530 ppm) <rhiz ome (-2890 ppm) croot(-22400 ppm). It was also found that the roots of this fern acc umulated a large amount of lead over the cell walls of cortex, while in the case of the petiol and leaf blade of the fern, lead w-as distributed over the cell walls of sieve tube of most of the stele. The content of lead (by dry weight) in the section of the fern roots increases in the order of stele (with endodermis, 3340 ppm) <cortex (with inner cortex, 12900 ppm) <<epidermis (with outer cortex, 18000 ppm). The accumulation of lead and its tolerance have some correlation with the concentration of sulfur in the tissues of this fern and its associated growing soils. The content of amino acids (by dry weight) in stele (with xylem and pholoem, 114 nmol/mg) is higher about two point fivefold than that in cortex and epidermis (45 nmol/mg). On the basis of these findings, main chemical species of lead in the tissues of Athyrium yokoscense are considered to be lead sulfate (cortex and epidermis parts) and metal complexes with pectic acid and some amino acids (stele part).