Tolerance to Zn toxicity in the halophyte Lepidium latifolium L. and the effect of salt on Zn tolerance and accumulation

Abstract

<p class="042abstractstekst">Halophytes exhibit a high cross-tolerance to multiple stresses that enable them to survive under harsh environmental conditions. We hypothesized that salt treatment in halophytes improves their tolerance against other stressors. To investigate the salt-mediated heavy metal tolerance in halophytes, <em>Lepidium latifolium </em>(Brassicaceae) was cultivated in the absence or presence of salt (100 mM NaCl) and excess Zn (200 μM ZnSO<sub>4</sub>), alone or in combination, for four weeks in the hydroponic medium. Salt treatment ameliorated the reduction of photosynthetic pigments in Zn-stressed plants and decreased Zn accumulation in the young leaves. The activity of peroxidase increased by both Zn toxicity and salt treatments; its maximum activity was achieved under the combination of both treatments associated with a significant reduction in malondialdehyde concentration. The activity of polyphenol oxidase increased by Zn stress alone or in combination with salt, accompanied by accumulation of free and cell wall-bound phenolics and enhanced lignin deposition in the leaves. Our results showed a mitigating effect of salt treatment in Zn-stressed plants through the activation of antioxidant defense and accumulation of phenolic compounds including flavonoids. Our results suggest <em>L. latifolium</em> as suitable species for revegetation and rehabilitation of saline soils contaminated with heavy metals.</p>