Actividad de enzimas del estrés oxidativo en plantas de tomate cv. Amalia en respuesta al plomo

Contamination of soils by heavy metals is a result of human activity, agriculture and industry. Among heavy metals, lead is a potential pollutant that in plants causes numerous symptoms of toxicity such as stunted growth, blackening of the root system and generalized chlorosis. The activity of superoxide dismutase enzyme (SOD; EC 1.15.1.1) and glutathione reductase (GR; EC 1.8.1.7) were determined in leaves and stem of tomato plants cv. Amalia using three lead (PbAc₂) concentrations (0, 50 and 100 mg/kg). Plants were sown in the period from September to December 2010 at greenhouse conditions, metal was applicated twice a week since the first true leave appeared until reproductive phase beginning, time at which samples were collected for evaluations. Significant differences were not found in protein concentration between treatments on leaves; its content in stems was reduced under the maximum concentration of PbAc₂. In leaves and stems the higher activity for both enzymes was at 50 mg/kg of PbAc₂, however no significant differences were found in stems. In stems a less activity of SOD was observed at the higher concentration used (100 mg/kg of PbAc₂) being significant different with the control and 50 mg/kg of PbAc₂. Staining of the antioxidant enzymes studies on polyacrylamide gel (PAGE) showed three different SOD isoforms in leaves and stems (one Mn-SOD and two Fe-SOD) and four GR isoforms in leaves and three in stems. The relative expression of SOD was analyzed with Real Time PCR and a higher expression at 100 mg/kg of PbAc₂ was found in leaves and stems. The cv. Amalia at 50 mg/kg of PbAc₂ activate its antioxidant defense system protecting plant from the damage that lead heavy metal could produce.