EFFECT OF Pb AND Zn COMBINED STRESS ON THE GROWTH AND ELEMENTS ACCUMULATION OF TWO DIFFERENT ECOTYPE SPECIES OF Iris L. IN ARTIFICIAL CONTAMINATED SOILS.

The effects of Pb and Zn combined stress on growth and Pb, Zn, Cu and Mn contents in the different parts of the seedlings of Iris halophila Pall, and I. pseudacorus L. were studied in pot culture. The results showed that Pb contents in the aboveground and underground parts of Iris halophila at 10 mmol·kg^-1 Pb reached to 411 μg·g^-1 and 2020 μg·g^-1, respectively, and Zn contents, 3588 μg·g^-1 and 2285 μg·g^-1, respectively, at the combined treatment of 5 mmol·kg^-1 Pb and 50mmol·kg^-1 Zn. Pb contents in the aboveground and underground parts of I. pseudacorus at 10mmol·kg^-1 Pb reached to 382μg·g^-1 and 1671μg·g^-1, respectively, and Zn contents, 2603μg·g^-1 and 3908μg·g^-1, respectively, at the combined treatment of 10mmol·kg^-1 Pb and 50mmol·kg^-1 Zn. Mn and Cu contents in both species presented a corresponding increase as single Pb levels enhanced and Mn contents decreased as Zn concentrations increased. The numbers and lengths of leaves and roots, and biomasses of both species were decreased significantly due to the large amount of Pb, Zn, Mn, Cu in the plants treated under 10 mmol kg^-1Pb and 50 mmol kg^-1Zn combined stress. The growths and developments of I. pseudacorus were effected more serious than those of I. halophilia. The negative correlation between the growth and the contents of Zn was found much more obvious than between the growth and the contents of Pb in two species of Iris L., which indicated that Zn was more toxic than that of Pb to the seedlings of I. pseudacorus and I. halophila. [ABSTRACT FROM AUTHOR]