en تنش فلزات سنگین Toxic ions stress پژوهشي Research The objective of this study was to determine <a name="OLE_LINK65"></a><a name="OLE_LINK62">the effects of lead (Pb) exposure on bioaccumulation, growth, and tolerance mechanisms in summer savory (<em>Satureja hortensis</em> L.). </a>Plants were subjected to different levels of <a name="OLE_LINK16"></a><a name="OLE_LINK15">Pb</a> concentrations including 0 (control), 5, 10, 25, 50 and 100 mg L^-1 in growing medium. Pb treatment led to significant increase in root and shoot Pb content. Calculation of BF, TF and TC revealed that Pb preferably accumulated in roots of <em>S.</em> <em>hortensis</em> and root to shoot transport was effectively restricted. Pb toxicity negatively affected plant growth as indicated by significant decrease in plant dry weight as well as roots and shoot length. Pb stress resulted in significant decrease in chlorophyll<em>-a</em>, chlorophyll<em>-b</em> and total chlorophyll content, whereas proline, soluble and reducing carbohydrates and anthocyanin content significantly increased as a result of Pb exposure. Specific activity of antioxidant enzymes including catalase and ascorbate peroxidase continuously increased as concentration of Pb in growing medium elevated. Based on our findings, due to high potential for Pb accumulation in root, <em>S. hortensis</em> may offer a feasible tool for phytostabilization purposes in mildly Pb contaminated soils.<br> &nbsp; antioxidant enzymes, heavy metals, lead, medicinal plants, phytoremediation, Satureja hortensis 63 75 http://jispp.iut.ac.ir/browse.php?a_code=A-10-975-1&slc_lang=en&sid=1 Ali Akbar Ghotbi-Ravandi a_ghotbi@sbu.ac.ir Yes Department of Plant Sciences and Biotechnology. Faculty of life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran دانشگاه شهید بهشتی تهران Seyed Majid Ghaderian ghaderian@sci.ui.ac.ir No Department of Biology, University of Isfahan, Isfahan گروه زیست شناسی اصفهان Zahra Azizollahi zahraazizollahi@yahoo.com No Department of Biology, University of Isfahan, Isfahan گروه زیست شناسی اصفهان