Enhanced essential oil and leaf anatomy of Schinus molle plants under lead contamination

Some plants species used in phytoremediation systems may produce essential oils of industrial interest but the heavy metal effects in these compounds remain unclear. This study aimed to investigate the effects of Pb on leaf anatomy and essential oil content, composition, and allelopathy of Schinus molle. Plants were submitted to 0, 0.25, 0.5, and 1.0 mM of PbNO3 for 90 days. Leaves were sampled and processed for anatomical analysis and essential oil extraction by hydrodistillation. The essential oil composition was identified by gas chromatography coupled to mass spectrometry and its allelopathy tested on lettuce seeds. Pb increased the size of secretory ducts in S. molle leaves. In addition, the essential oil content in S. molle leaves was increased by Pb. For control plants, four compounds were found and the α-muurolol and spathulenol were the major components. Under Pb contamination, 19 different compounds were identified. Pb exposed plants increased spathulenol content but reduced α-muurolol. Likewise, germacrene, y-cadinene, and caryophyllene percentages appear at significant levels. Essential oils developed under Pb showed higher inhibition of lettuce seed germination. Therefore, Pb increases the yield and allelopathy of the essential oils on S. molle plants and this higher oil production is related to larger leaf secretory ducts.