Both tartaric and pantothenic acids promote Pb-phytoextraction potential of sunflower by regulating calcium and phosphorus uptake

Phytoextraction of Pb is a challenging task due to its extremely low mobility within soil and plant systems. In this study, we tested the influence of some novel chelating agents for Pb-phytoextraction using sunflowers. The Pb was applied at control (0.0278 mM) and 4.826 mM Pb as Pb(NO ₃ ) ₂ through soil-spiking. After 10 days of Pb addition, four different organic ligands (aspartic, ascorbic, tartaric, and pantothenic acids) were added to the soil at 1 mM concentration respectively. In the absence of any chelate, sunflower plants grown at 4.826 mM Pb level accumulated Pb concentrations up to 104 µg g ^-1 DW in roots whereas, 64 µg g ^-1 DW in shoot. By contrast, tartaric acid promoted significant Pb accumulation in root (191 µg g ^-1 DW; +45.5%) and shoot (131.6 µg g ^-1 DW; +51.3%). Pantothenic acid also resulted in significant Pb-uptake in sunflower shoots (123 µg g ^-1 DW; +47.9%) and in roots (177.3 µg g ^-1 DW; +41.3%). The least effective amongst the chelates tested was ascorbic acid but it still contributed to +39.0 and 45.2% more Pb accumulation in sunflower root and shoots. In addition, plant growth, biochemical, and ionomic parameters were positively regulated by organic chelates. Especially, an increase in the leaf Ca, P, and S was evident in Pb-stressed plants in response to chelates. These results highlight that the use of biocompatible organic chelates positively alters plant physio-biochemical traits contributing to higher Pb-sequestration in sunflower plant parts.