Gibberellic Acid and Tween 20 Increases Napier Grass Tolerance to Synthetic Pyrethroid

The wide use of synthetic pyrethroids has increased their contamination in agricultural soil, so removing this pollutant from agricultural sites is necessary. Phytoremediation offers promise for agricultural soil decontamination as it is an environmentally friendly and green method. In this study, Napier grass cv. Pakchong 1 (Pennisetum purpureum x Pennisetum Americanum), cuttings with or without soaking in gibberellic acid (GA3) with and without the surfactant Tween 20, were planted in synthetic pyrethroid contaminated soil for 20 days. The results showed that the synthetic pyrethroid reduced shoot and root growth, reduced the pigment content and increased the proline content in the leaves of Napier grass cv. Pakchong 1, and GA3 soaking alone was the most appropriate method to alleviate synthetic pyrethroid phytotoxicity. However, planting with Napier grass cv. Pakchong 1 did not enhance soil biodegradation of cypermethrin, deltamethrin, permethrin, and fenvalerate. Napier grass did not accumulate synthetic pyrethroids within the shoot and root tissue, as the bioconcentration factor for each compound was below 1. Indigenous soil microorganisms caused a decrease in these synthetic pyrethroids. Napier grass could tolerate and grow well in pyrethroid-contaminated soil, and a method to enhance the plant’s capacity to remove pyrethroid from the soil should be developed.