The aim of this research was to investigate the effect of one plant activator on peroxidase (EC 1.11.1.7) and protease (EC 4.3.1.1) activity in Solanum lycopersicum Riogrande and H2274 varieties. Plant activator was applied to 10 weeks old seedlings in recommended dose, two and four fold doses (2,4 and 8 ml/L) by spraying to the leaves under in vivo conditions. The leaves of the seedlings were harvested for analysis 24 and 48 h after plant activator applications. All of the experiments were replicated three times. Peroxidase activity changing in S. lycopersicum varieties while compared with control group. 48 h after 8 ml/L activator application in Rio Grande and H2274 varieties POX activity increased as 248% and 247.4% respectively. Protease activity changing in S. lycopersicum varieties was compared with the control group. 48 h after 4 ml/L activator application in RioGrande and H2274 varieties PRO activity increased as 90.6% and 83.7%, respectively. Plant activator application has changed the total peroxidase and total protease levels depending to the time and concentrations in different levels. Thus, the use of chemicals with low doses and activators can prevent different plant related diseases by increasing the efficiency of self defence mechanisms in plants by virtue of which our country can hold an important place in agriculture in future and also foreign sales will contribute to resolve the phyto-pathological problems of tomato
