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Boron (B) is an essential micronutrient for normal growth of higher plants. On the other hand, its toxicity is also a significant problem that can limit plant growth on soils of arid and semi-arid environments in agricultural regions across the world. In this study, two tomato (Lycopersicon esculentum Mill.) varieties (SC2121 and SAFARI F1) are used, and toxic effects of B treatment (3 mM) were studied. Germination was not affected, and seeds of both varieties germinated nearly to 100%. These in vitro germination experiments were accomplished in MS medium. Malondialdehyde (MDA) content, and antioxidant enzyme activites (superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR)) were investigated in root and shoot tissues of tomato seedlings.

Oxidative damage increased with 3-mM B treatment in tissues of SC2121 plants compared to control, and antioxidant enzyme activities were decreased, except APX. B toxicity inhibited only CAT activity in root tissues, but CAT, GR, SOD, PDX and APX activities were inhibited in shoot tissues of SAFARI F]. However, B toxicity in this variety did not cause oxidative damage. Root tissue of SAFARI F1 variety, in particular, was found to be a better protection than SC2121. This might indicate that SAFARI F1 variety is based on the protection of antioxidant enzymes. However, similar protections against B toxicity were not detected in shoot tissues of both varieties.