Antioxidative defense activation in soybean cells

Suspension-cultured, photoheterotrophically grown, green soybean cells (Gly cine max L,) were used to investigate alterations in the cellular contents of ascorbate and glutathione, as well as specific activities of antioxidati ve enzymes, elicited by salicylic acid (SA) and BTH [benzo(1,2,3) thiadiazo le-7-carbothioic acid S-methylester]. Both antioxidants were positively reg ulated by 48-h incubations with SA and BTH, respectively; the latter induce d a stronger increase in antioxidant levels compared to SA. The specific ac tivities of glutathione reductase, monodehydroascorbate reductase and gluta thione S-transferase increased strongly in soybean cells as a response to b oth SA and BTH. The enzyme activations observed were in the range of 2-8-fo ld, Catalase activity was also increased 2-fold by SA but decreased when ce lls were incubated with BTH. These results indicate an activation of the ce llular antioxidative system at both the antioxidant and enzyme level. In ad dition, the effects of SA and BTH on phytotoxicity exerted by the peroxidiz ing herbicide oxyfluorfen were investigated. Both compounds protected soybe an cells from herbicide-induced lipid peroxidation in a time- and concentra tion-dependent manner and strongly suppressed the herbicide-induced accumul ation of protoporphyrin IX. SA as well as BTH antagonize the action of pero xidizing herbicides.