Changes in the level of acid soluble tiols in plant tissues, as physiological markers of heavy metals stress.

CHANGES IN THE LEVEL OF ACID SOLUBLE TRIOLS IN PLANT TISSUES, AS PHYSIOLOGICAL MARKERS OF HEAVY METALS STRESS A1berto Rivetta, Noemi Negrini and Maurizio Cocucci Department of Plant Physiology and Soil Chemistry, University of Milan, Milan, Italy The use of biological systems and particularly the changes in biochemical and physiological parameters in plants could be an useful tool in monitoring polluted environments. It is known that plants exposed to heavy metals can accumulate thiols, low molecular weight substances rich in -SH groups. In this work, we consider the possibility to use the changes in the level of acid soluble thiols, as physiological markers of heavy metals stress. The results indicated that thiols level in organs of different plant species early and strongly increased in plants grown in the presence of increasing Cd2+ concentrations,. Thiols level also increased in plants grown on a standard substrate containing different amounts of exogenous added Cd2+ or heavy metals polluted soil, although growth parameters such as fresh and dry weight, protein and chlorophyll contents did not vary with respect to the controL In these two cases, when Cd2+ in plants tissues reached the same level (30 nmol i' fw) the increase in thiols level was higher in plants grown in the presence of polluted soil than Cd2+. These data suggest that the changes in thiols level may be considered a physiological parameter of general plant stress and may be easily used also in field conditions. Moreover, using glutathione affinity chromatography, preliminary data suggest that changes in glutathione-dependent activities, in particular glutathione transferase, may be used as very sensible markers of Cd2+ stress