Physiological performance and growth of Viburnum tinus L. on phytoremediated sediments for plant nursing purpose

Sediments are fundamental resources for productive activities like plant nursing, which are also likely to be responsible of their loss. In contrast, other activities like the dredging of canals and waterways involve the extraction and continuous accumulation of sediments. Most dredged sediments are polluted, and need to be stocked and transported to landfills, with extremely high costs for transport and management. To address these problems, a low-cost remediation methodology was previously developed to decontaminate sediments which were tested for use in plant nursery field plantations located in Pistoia (Italy). The phytoremediated sediments were mixed in percentages of 33% and 50% with alluvial soil, which itself was used as control. We studied the characteristics of these mixtures, and the physiological response and growth of Viburnum tinus L. grown on each substrate, as well as its corresponding root ball. Substrates with sediments showed quick water infiltration and no waterlogging, in sharp contrast to what was observed in autumn in the control. Despite a rainy summer, V. tinus demonstrated a good acclimation to the different substrates, showing the lowest leaf water potentials in mixed substrates and no signs of stress. No differences in leaf carbon assimilation or transpiration were observed among substrates, while in late August plants grown on substrates with sediments showed a higher performance index for energy conservation from photons absorbed by PSII to the reduction of intersystem electron acceptors. In the 50% mixture, there was also an enhancement of electron transport from PSII to PSI. Moreover, no differences in growth and biomass were found. Plants in all substrates showed some thin-root mortality, likely due to the persistent rainfall, though a higher number of plants with dead roots was observed in control. Thanks to the dense and fibrous root apparatus of V. tinus, the mixture with 33% sediments produced satisfactory results even for the root ball, resulting in less deformation and a lower breakage percentage.