Antioxidant capacity and chemical composition of Carum copticum under PEG treatment.

Abstract

<span style="font-family: Calibri;"><span style="font-size: medium;"><span>Drought stress is one of the main non-biological factors limiting the growth and yield of plants in dry and semi-dry regions of the world. Plants are the source of much chemicals derived from secondary metabolism. <em>Carum copticum</em> is a plant from the Apiaceae family with the seeds containing 2-4% the essential oil which are rich in monoterpenes such as thymol and are widely used as an antibacterial agent.</span><span> This experiment was conducted in order to evaluate the effects of drought stress on </span><span>physiological parameters </span><span>and essential oil properties of seedlings and callus of</span><em><span> C. copticum</span></em><span>. For this purpose, </span><span>seeds of</span><em><span>C. copticum</span></em><span> were cultured in </span><span>Murashige and Skoog</span><span> medium containing 0, 2, 4, 6, and 8% PEG</span><span>.</span><span> Also</span><span>,</span><span>calluses cultured were in MS medium containing </span></span><span><span style="font-size: medium;">0.25 mg.L</span>^{<span style="font-size: small;">-1</span>}</span><span><span style="font-size: medium;"> 2, 4-Dichlorophenoxyacetic acid,</span></span><span><span style="font-size: medium;"> and 1 mg.L</span>^{<span style="font-size: small;">-1</span>}<span style="font-size: medium;"> benzyl amino purine<span> and different levels of PEG</span></span></span><span style="font-size: medium;"><span>.</span><span> After PEG treatment for 4 weeks, results showed that drought stress decreased chlorophylls and carotenoids contents while it increased anthocyanin, phenolic compounds, protein contents, and CAT and APX activities. Unlike CAT and APX, water deficit induced a significant reduction in superoxide dismutase activity. The content of reducing sugars and proline increased progressively when drought stress increased. Furthermore, PEG changed the essential-oil composition in shoots and calluses. Drought stress increased thymol and p-cymene concentration, though it decreased γ-terpinene.</span><span> In general, these results showed the high tolerance of <em>C. copticum </em>to drought stress and also revealed positive effects of drought on the antioxidant activities and essential oil composition.</span></span></span>