Exposure to Lead (Pb) Induced Changes in the Metabolite Content, Antioxidant Activity and Growth of Jatropha curcas (L.) Amal A. A. Mohamed 1 & Mahmoud H.O. Dardiry 2 & Abdul Samad 3 & Eman Abdelrady 4 Received: 25 August 2019 /Accepted: 24 October 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Lead (Pb) is a rapidly increasing heavy metal due to different human activities. It is highly toxic to plants, and its toxicity can impair various morphological, physiological and biochemical functions in plants. In the present study, an experiment was designed to investigate the response mechanisms to counteract Pb in the seedlings of Jatropha curcas. For this purpose, Pb accumulation, metabolite contents, antioxidant activity and accumulation of antioxidants such as phenolics and flavonoids were evaluated. The transcription levels of two genes, metallothioneins (JcMT2a) and phenylalanine ammonia-lyase (JcPAL), in- volved in the metal detoxification mechanism were also analyzed. The seedlings of J. curcas were hydroponically treated with different doses of Pb (0, 0.5, 5, 10, 20 and 40 mg/L). With increasing Pb dose in the nutrient solution, its accumulation was in the following pattern: roots> stems> leaves. The seedlings showed higher tolerance index (TI) in the highest Pb concentration. The dry weights of roots, stems and leaves, and the total content of proteins were significantly decreased with increasing Pb concentration. However, the photosynthetic pigments, total phenolic and flavonoid compounds were increased in response to elevated Pb concentrations. This was associated with increasing of total antioxidant capacity and radical scavenging activity. Relative transcription of JcMT2a and JcPAL showed distinct pattern in roots and leaves. Integral mechanism for Pb stress tolerance was likely accomplished by activation of antioxidant defense system which was evidenced by up regulation of JcPAL. Our study provides biochemical and genetic basis of Pb-induced defense mechanisms for metal detoxification in J. curcas. Keywords Jatropha curcas . Pollution . Lead . Phytoremediation . Phenylalanine ammonia-lyase . Metallothionein Abbreviations AA Ascorbic acid BAF-L bioaccumulation factor in leaves BAF-R bioaccumulation factor in root BAF-S bioaccumulation factor in stem Chl a chlorophyll a Chl b chlorophyll b DW-L dry weight of leaves DW-R dry weight of roots DW-S dry weight of stems Jcmt2a-L metallothionine of J. curcas in leaves Jcmt2a-R metallothionine of J. curas in root JcPAL-L Phenylalanine ammonia-lyase of J. curcas in leaves JcPAL-R Phenylalanine ammonia-lyase of J. curcas in root TAC total antioxidant capacity Tf total flavenoids TI tolerance index TP total proteins TPh total phenolics TrF-R:S translocation factor (root to stem) TrF-S:L translocation factor (stem to leaves) Communicated by: Yuan Qin Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12042-019-09244-0) contains supplementary material, which is available to authorized users. * Amal A. A. Mohamed amal.mohamed2@aswu.edu.eg; abdul.samad@ait.ac.at 1 Botany Department, Faculty of Science, Aswan University, Aswan 81528, Egypt 2 Egyptian Environmental Affairs Agency, Branch, Elsadaat Road, Aswan, Egypt 3 AIT Austrian Institute of Technology GmbH, Center for Health and Bioresources, Bioresources Unit, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria 4 Chemistry Department, Faculty of Science, Aswan University, Aswan 81528, Egypt Tropical Plant Biology https://doi.org/10.1007/s12042-019-09244-0