Higher Tl bioaccessibility in white mustard (hyper-accumulator) grown under the soil than hydroponic conditions: A key factor for the phytoextraction use

Abstract

The paper deals with the thallium (Tl) access into the white mustard (Sinapis alba L.). We were comparing two approaches: A - hydroponic, B - semi-hydroponic (artificial soil). The kinetics of Tl plant uptake at different available Tl doses (0.1, 0.05 and 0.01 mg L^-1) was tested. It was revealed that the hydroponic arrangement did not accelerate the plant uptake of Tl. The concentration of plant Tl was surprisingly roughly double under the semi-hydroponic (artificial soil) conditions as compared to the hydroponic system; the highest Tl concentrations were detected in stems, proving an important role of plant grown strategy on Tl bioaccessibility. We found that almost independently of the initial dose of Tl the juvenile stadium of the mustard can preserve1-2% of the total Tl pool. Up to 95% of this Tl dose is stored in the shoots. The different strategy of the plant growing may strongly affect the path of Tl incorporation. The total Tl input into the leaf tissue in hydroponics may be from 69% (p = 0.01) explained by parallel assimilation of Ca. In contrast, the Tl entry into the leaf grown on the artificial soil could be limited by Mn path (R² = 0.91, p = 0.01).

Keywords: Artificial soil; Hydroponic; Phytoremediation; Plant physiology; Plant thallium uptake.