COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS

Boron (B) is an essential micronutrient for plants through paticipating key reactions such as reproduction, development, and regeneration. Similar to its deficiency, its over-concentations possess toxic effects on plant growth. In this work, possible boron toxicity was researched through evaluating alaterations in antioxidant enzymes, oxidative stress biomarkers, and chlorophyll contents for two types of lentil species as red (native) and green (winter flake 11) lentil (Lens culinaris L. cv) cultivars, which are indigenous to Turkey. Ten days old seedling lentil plants were subjected to low as 0.5, 1.0 mM and high 2.0 and 5.0 mM boric acid treatments for 7 days. B worked as a growth-promoting nutrient for 0.5, 1.0, and 2.0 mM concentration by enhancing length and weight of both shoot and root tissues, while it started showed its suppression effect on these tissues at 5-mM cocentration, which were obtained more dramatic for green lentil in comparison to red lentil. In contrast to this, oxidative stress markers such as MDA, H2O2, and proline concentrations showed increasing trend for 0.5, 1.0, 2.0, and 5.0 mM B treatment, accompanied with a change in photosynthetic pigment concentrations (p < 0.01). MDA in red lentil shoot control was 30,3871 (mu mol/gFW) and it was significantly increased to 36,5806 and 51,7414 by the 2.0 and 5.0 B rates, respectively. However, enzymes in anti-oxidation metabolism include superoxide dismutase (SOD), guaiacol peroxidase (GPX), lipoxygenase (LOX), glutathione peroxidase (GSH-Px) activities were obtained higher in high-B-treated groups, while decreased and stable activities were obtained for catalase (CAT) and ascorbate peroxidase (APX) enzymes. CAT and APX activities were higher than those were obtained for 2.0 and 5.0 mM B treatments in both root and shoot tissues. The lentil species manipulated their metabolism to suppress B-stress, and enhanced growth in shoot and root tissues up to 5-mM B stress even though oxidative stress markers showed increasing trend from low B concentrations, 1.0 mM. Therefore, B stress can be claimed as doubled edge sword for these lentil species