Foliar Application of Salicylic Acid and DA-6 on Swithgrass (Panicum virgatum L.) Grown in Pb-Contaminated Soil; Implications for Phytoextraction

Lead (Pb) soil contamination is widespread and poses a threat to human health. Even chronic exposure to low levels of Pb contaminated soils is potentially harmful to organisms. Remediation of Pb-contaminated soil can be accomplished through phytoextraction, a technique that uses plants and associated soil microorganisms. The North American native switchgrass (Panicum virgatum L.), a second-generation bioenergy crop was used in this study due to its ability to produce high biomass and grow on marginal lands. In this study the effects of exogenous foliar application of the plant growth regulators diethyl aminoethyl hexanoate (DA-6) and salicylic acid (SA) were examined separately but in conjunction with the soil-fungicide propiconazole and soil chelate nitrilotriacetic acid (NTA) in order to optimize phytoextraction of Pb. Plants were grown under controlled conditions using highly Pb-contaminated (5802.5 mg kg(-1)) soil derived from a superfund site. Foliar application of the plant growth regulator DA-6 resulted in significantly higher Pb concentrations in the foliage of plants compared to Control plants. The DA-6 did, however, not improve plants dry mass (DM). Foliar application of salicylic acid resulted in significantly greater DM of the foliage compared to Control plants. The DM of plants treated with foliar application of salicylic acid was 46% higher than those of Control plants. Foliar application of salicylic acid did not improve significantly Pb concentration of foliage compared to Control plants. The findings reported in this study will potentially improve phytoextraction by switchgrass grown in Pb contaminated soils.