Effect of salicylic acid (SA) on Nicotiana tabacum grown under lead (Pb) stress

Abstract

Lead (Pb) is one of the main environmental toxicant that cause physiological and biochemical dysfunction in plants. Compounds involved in modification of heavy metals stress are important to mitigate the toxicity effect of heavy metals. Salicylic acid (SA) is one of the compounds that has the ability to counteract Pb toxicity. The aim of this study was to investigate the effects of SA on the physiology, oxidative level, Pb content and transcript level of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in Pb-treated N. tabacum. N. tabacum was propagated and treated with SA and Pb. The morphology and physiology of Pb-treated N. tabacum were visually observed and measured. Histochemical staining of diaminobenzidine (DAB) and nitro blue tetrazolium (NBT) was conducted to assesses the effect of SA on the accumulation of O2– and H2O2, and inductively-coupled plasma mass spectrometry (ICP-MS) was performed to examine Pb content and Pb translocation factor in Pb-treated N. tabacum. The transcript levels of SOD, CAT and POD were measured using real time PCR. The present study demonstrated that the application of SA improved growth parameters, abolished the accumulation of hydrogen peroxide (H2O2) and superoxide (O2–), and reduced the content of Pb in leaves of Pb-treated N. tabacum. Transcript level of SOD, CAT and POD were not regulated by SA and Pb treatments. SA mitigation of Pb toxicity in Pb-treated N. tabacum might be not at the level of gene expression, but affected the uptake, detoxification, and sequestration of Pb. The results of this study has shown the importance of SA in alleviating the Pb stress and suggests that SA could be used as a potential growth regulator to improve plant growth under Pb stress.