SALICYLIC ACID DECREASES Cd TOXICITY IN MAIZE PLANTS

The present study is focused on the possible mediatory role of salicylic acid (SA) in photosynthesis under cadmium (Cd) toxicity. Maize seeds were sterilized and divided into two groups. One half of the seeds was presoaked in 500 μM SA solution for 6 h and then both groups were allowed to germinate for 3 days. Plants were grown for 12 days in Hoagland solution at 22/18 oC under 16/8-h light/ dark periods and 120 μmol. m-2s-1 PAR. All seedlings (without H2O and SA controls) were transferred to Cd-containing solutions (10, 15, 25 μM) and grown for 12 days. Exposure of plants to Cd caused a gradual decrease in chlorophyll content, the effect being expressed to a higher extent at 25 μM Cd. Pretreatment of seeds with SA alleviated the Cd negative effect on this parameter. The rate of CO2 fixation was lower in Cd-treated plants and the inhibition was partially overcome in SA-pretreated plants. A drop in the activities of RuBPC and PEPC was observed in Cdtreated plants. Pretreatment with SA alleviated the inhibitory effect of Cd on the studied enzymatic activities. Proline production and the rate of lipid peroxidation in Cd-treated plants were much lower in SA-pretreated plants.