Copper exposure leads to changes in chlorophyll content and secondary metabolite profile in Lantana fucata leaves

Abstract

Cultivation of plants in environments polluted by metals at toxic levels can affect the biosynthesis of secondary metabolites. Here, we analysed the effect caused by excess copper on the concentration of chlorophylls a and b and the profile of secondary metabolites of Lantana fucata leaves. Five copper (Cu) treatments (mg Cu kg−1 soil) were tested: T0, 0; T1, 210; T2, 420; T3, 630; and T4, 840. We found that the concentrations of chlorophylls in the plants decreased when compared to the control. However, this did not lead to a significant reduction in its growth, possibly due to the low translocation of the metal to shoots and the activation of plant defence systems to tolerate the environment in which they are exposed, increasing the emission of lateral roots and activating pathways for the production of secondary metabolites. Therefore, we found a decrease in the concentration of two key compounds in secondary metabolism, p-coumaric and cinnamic acids in treatments with higher copper concentrations. We also found an increase in phenolics. Decreases in p-coumaric and cinnamic acids may have occurred because these are precursors in the synthesis of phenolic compounds, which are increased in the high Cu treatments. Six secondary metabolites were characterised, described for the first time for this plant species. Thus, the presence of excess Cu in the soil may have triggered an increase in the amount of reactive oxygen species in the plants, which that led to the synthesis of antioxidant compounds, as a defence strategy.