Changes in chlorophyll spectral characteristics in rye seedlings grown under heavy metal stress

Abstract

Heavy metals produce many severe toxic effects while taken up by plants in higher concentrations. Küpper et al. (1996, 1998) demonstrated that the substitution of the central Mg ion in chlorophyll by heavy metals in vivo is one of the most important damages observed in the photosynthetic apparatus of stressed plants. Here we present the results of the effects of Cd, Cu, Hg, Ni, Pb and Zn on spectral characteristics of chlorophyll in rye seedlings grown under heavy metals stress. Heavy metals were applied to the nutrient medium at 500 mM concentration after 4 days of growth at light intensity of 150 mmol m-2s-1, 16/8 h day/night regime. After next 7 days of growth at the above conditions second leaves were subjected to subsequent analyses. Absorption, fluorescence induction and emission spectra were taken from the leaves, isolated chloroplasts and chlorophyll extracted from metal-treated seedlings. We also performed the measurements of chlorophyll a fluorescence induction kinetics by the modulated fluorescence technique. Chlorophyll spectral changes, disturbances in energy transfer in photosynthetic antennae, as well as changes in structural properties of the major light-harvesting complex (LHCII) were observed in heavy-metal treated plants. Küpper H, Küpper F, Spiller M, 1996. J.Exp.Bot. 47: 259-266. Küpper H, Küpper F, Spiller M, 1998. Photosynth. Res. 58: 123-133.