Cucurbits and their secondary metabolites as stimulators of biological remediation of soil contaminated with phenoxy acid herbicides

Abstract

The overuse of phenoxy herbicides (PHs), i.e. 2,4-D (2,4-dichlorophenoxyacetic acid) and MCPA (2-methyl-4-chlorophenoxyacetic acid) can cause uncontrolled spread of PHs residuals in the environment. Hence, the development of nature-based solutions which employ the properties of ecosystems in order to detoxify the environment is an important step for removal of pollutants. Therefore, the main aim of this PhD dissertation was to verify if cucurbits and their characteristic secondary metabolites (PSMs) (ferulic acid - FA and syringic acid - SA) stimulate the biodegradation potential of environment for removal of structurally related PHs and mitigate the toxic effect of PHs in the environment. The experiments were divided into two subsections: microbial cultures and greenhouse experiments. Hence several microbial and physico-chemical analyses were conducted. The stimulating effect of cucurbits growth and PSMs on the biodegradation potential of soil for removal of PHs was dependent on selection of PSM and initial concentration of PHs. The functional diversity of unplanted and planted soil was influenced positively by the amendments with selected PSM (SA) and PH (MCPA). Addition of phenolic compounds had a great effect on the leaves endosphere. Structural diversity analysis revealed also that amendment of soil with SA promotes the occurrence of bacterial taxa that can potentially support the biodegradation of PHs. The measurements of PHs concentration showed that the stimulating effect of PSMs was observed only in the case of SA and lower initial dose of MCPA. Ecotoxicity analyses proved that higher potential of toxicity mitigation was observed for SA and zucchini.