Application of signaling molecules has gained immense importance in improving the phytoremediative capacity of plants. This study investigated the possible role of melatonin (MEL) as a signaling molecule in ameliorating lead (Pb)-induced oxidative injury in safflower seedlings. Pot grown 10-day-old safflower seedlings were exposed to 50 μM Pb (NO3)2 alone and in combination with different MEL concentrations (0-300 μM). Exposure to Pb, resulted in a severe oxidative stress, which was indicated by reducing biomass production and enhancing the level of oxidative stress markers (e.g. MDA and H2O2). Addition of exogenous MEL considerably decreased Pb uptake and its root-to-shoot translocation while, biomass production of roots, stems and leaves increased significantly. With MEL application a marked increase in reduced glutathione (GSH) content in leaves and roots was noted as compared with Pb treatment alone. In leaves the activity of enzymes involved in glyoxalase system increased markedly by adding MEL to Pb-sressed plants. In response to increasing MEL treatments, the phytochelatin content of leaves increased substantially in comparison with Pb treatment alone. These findings confirmed that MEL can alleviate Pb toxicity by reducing Pb uptake and its root-to-shoot translocation along with modulating different antioxidant systems. The results also showed that despite the insignificant effect of melatonin on the improvement of Pb phytoremediation potential, the application of this signaling molecule can improve the survival of safflower in Pb-contaminated soils by stimulating antioxidant defense mechanisms.

中文翻译：

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褪黑素减轻了红花（Carthamus tinctorius L.）幼苗中铅诱导的氧化损伤。

信号转导分子的应用在提高植物的植物修复能力方面具有极其重要的意义。这项研究调查了褪黑激素（MEL）作为信号分子在改善铅（Pb）引起的红花幼苗氧化损伤中的可能作用。盆栽的10天大红花幼苗单独暴露于50μMPb（NO3）2，并与不同的MEL浓度（0-300μM）接触。暴露于Pb会导致严重的氧化应激，这可以通过减少生物量产生并提高氧化应激指标（例如MDA和H2O2）来表明。外源MEL的添加大大降低了Pb的吸收及其从根到茎的转运，而根，茎和叶的生物量生产显着增加。与单独的铅处理相比，在施用MEL的情况下，叶和根中的谷胱甘肽（GSH）含量降低明显增加。在叶片中，通过向含铅的植物中添加MEL，可显着提高乙二醛酶系统中涉及的酶的活性。响应于增加的MEL处理，与单独的Pb处理相比，叶片的植物螯合素含量显着增加。这些发现证实，MEL可以通过减少Pb的吸收及其从根到茎的转运以及调节不同的抗氧化剂系统来减轻Pb的毒性。结果还表明，尽管褪黑素对Pb植物修复潜力的改善作用不明显，但该信号分子的应用可以通过刺激抗氧化剂防御机制来提高红花在Pb污染土壤中的存活率。