Phytoextraction of trace elements (TE) using woody species is an economically challenging soil remediation approach because of the long time needed. Yet, some trees contain alkaloids that can be exploited along structural components to enhance biomass value. As alkaloids are thought to be involved in plant defence mechanisms, we hypothesized that potentially hostile phytoremediation conditions could increase their level. Camptothecin in Camptotheca acuminata and 1-deoxynojirimycin in Morus alba were measured from trees grown in a field in presence of Cu, Pb and Zn all together, and from M. alba grown in a greenhouse in presence of Cd or other abiotic stressors (NaCl and bending). The trees did not extract TE in the field, but M. alba stems accumulated Cd in the greenhouse experiment, with no consequence on stomatal conductance and leaves pigments concentration. Camptothecin and 1-deoxynojirimycin concentrations were preserved under all experimental conditions, as was biomass yield, and phenolics were slightly increased in M. alba exposed to TE. This study provides evidence that valuable and persistent alkaloids and phenolics can be extracted from trees facing phytoremediation-associated stresses, without a negative impact on their quantity and on biomass yield. Such products could generate a sustainable stream of revenues during phytoremediation.
Keywords: Camptotheca acuminata; Morus alba; Soil contamination; alkaloids; phytoextraction; wood extractives.
There is scarce data on tree alkaloid content and scarcer data on how it is affected by exposure to trace elements in a phytoremediation context. We provide evidence that the content of two specific alkaloids is not altered in Morus alba and Camptotheca acuminata exposed to moderate to elevated levels of contaminating trace elements. The manuscript introduces the use of M. alba for phytoremediation in the Americas and is the first to propose the use of C. acuminata on trace element contaminated sites to produce camptothecin, a valuable anticancer alkaloid.