Effect of palmitic acid on remediation of Scripus triqueter and enzymes activities of the rhizosphere soil in the simulated diesel-spiked wetland

• Palmitic acid inhibited the height, stem weight, root weight of ST.
• The activity of SOD and CAT in root and stem decreased in STDP compared with STD.
• The activities of PPO and DHG were lower in STDP than those in STD.
• Compared to STD, the concentration of residual diesel in STDP was significant higher.
• Palmitic acid might act as an allelochemical to ST and rhizosphere soil enzymes.

Scripus triqueter (ST), an oil tolerant plant in the wetland of Huangpu-Yangtze river estuary (HYRE) can be used for phytoremediation. As a dominant root exudate of the ST, palmitic acid was examined for its impact on the ST and the rhizosphere soil enzymes of simulated diesel-spiked wetland. Pot experiment showed that palmitic acid inhibited the growth (height, stem weight, root weight) of the ST and the activities of soil enzymes. The activities of superoxide dismutase (SOD) and catalase (CAT) in the root and stem of the ST decreased in diesel-spiked soil planted with ST and inoculated with 400 mg kg−1 of palmitic acid (STDP) compared with those in the diesel-spiked soil planted with ST (STD). It was found that the activities of polyphenol oxidase (PPO) and dehydrogenase (DHG) were lower in the STDP than those in the STD throughout the experiment. Compared to the STD, the concentration of residual diesel in the STDP was significantly higher, indicating that inhibited degradation abilities of soil microbes and plants. The results suggested palmitic acid might act as an allelochemicals to the ST and the rhizosphere soil enzymes in the simulated diesel-spiked wetland.