Influence of Brassinosteroids on Antioxidant Enzymes Activity in Tomato Under Different Temperatures

The effect of brassinosteroids (BRs) on catalase (EC 1.11.1.6), peroxidase (EC 1.11.1.7) and superoxide dismutase (SOD, EC 1.15.1.1) activity in tomato leaf discs was analyzed at 25 and 40 °C. Tomato leaf discs were preincubated for 24 h in Petri dishes with 24-epibrassinolide (EBR) or a polyhydroxylated spirostanic analogue of brassinosteroids (MH5). Both concentrations (10.60 and 2.12 nM) of EBR and MH5 stimulated the activity of SOD at 25 and 40 °C, the MH5-stimulated increase of this enzyme activity was greater. Peroxidase activity was unaffected at 25 °C, while at 40 °C this activity was enhanced by both compounds. The changes in catalase activity markedly depended on the structure BRs, doses and temperature. The results suggest a possible role of EBR and MH5 in the reduction of cell damage produced by heat stress due to induction of enzymatic antioxidants.