Lead tolerance, accumulation and translocation in two Asteraceae plants: Limbarda crithmoides and Helianthus annuus

Lead (Pb) is known as a toxic metal and a non-essential element for plant metabolism and growth. This work investigated the phytotoxicity of Pb induced stress and assessed the accumulation potential of Pb in two Asteraceae plants; Limbarda crithmoides and Helianthus annuus. The experiments were performed for 45 days using different concentrations of Pb (0, 100, 200, 300 and 500 mu mol.L-1). The dry biomass production in shoots and roots of Limbarda crithmoides were significantly enhanced with the increase of Pb doses in the growth medium, Helianthus annuus plants showed a modest variation in shoot and root dry weights, but without any significant difference as compared to the untreated plants. In addition, metal tolerance index values determined in the shoots and roots of these two species followed a similar trend as the dry weight contents. Both phenolic compounds and flavonoids were significantly increased in the two Pb treated species in comparison to the untreated plants (except flavonoid content of Limbarda crithmoides roots). Total inorganic nitrogen and macronutrient uptake were also assessed, and the two species showed different behaviour when varying Pb concentrations. Moreover, the two species accumulated Pb in their roots more than in the shoots (less than 1000 mu g.g(-1) DW) with a low translocation from roots into shoots (translocation factor < 1). Our findings demonstrated that both Limbarda crithmoides and Helianthus annuus were tolerant to Pb stress; nonetheless, the two species could not be classified as Pb hyperaccumulators. (C) 2022 SAAB. Published by Elsevier B.V. All rights reserved.

Automated summary

This study investigated the phytotoxicity of lead (Pb) and accumulation potential in Limbarda crithmoides and Helianthus annuus. The results showed that Pb doses enhanced the biomass production in Limbarda crithmoides shoots and roots, while Helianthus annuus showed modest variation. Phenolic compounds and flavonoids were increased in both species under Pb treatment. Pb accumulation was higher in roots than shoots, with low translocation factor. The two species exhibited tolerance to Pb stress but were not classified as hyperaccumulators.