Ligands involved in Pb immobilization and transport in lettuce, radish, tomato and Italian ryegrass

Abstract

Lead (Pb) and other heavy metals represent a great source of concern in agriculture because they may disperse from polluted sources and accumulate in crop organs. This research study was performed with three edible crops and one pasture species (lettuce: Lactuca sativa L. cv. Romana; radish: Raphanus sativus L. var. radicicola; tomato: Lycopersicon lycopersicum L. Karst.; Italian ryegrass: Lolium multiflorum Lam). It was aimed at (1) assessing how species affect Pb distribution among plant organs, (2) determining the extent to which Pb is localized in edible organs, and (3) ascertaining whether it could be possible to distinguish which compounds are responsible for the transport of Pb from one plant organ to another and which compounds are responsible for the accumulation of this metal inside each plant organ. The experiment was conducted in the greenhouse. Plants were grown in plastic pots using a Pb-spiked sandy soil as substrate. Total Pb concentrations in different plant organs and in soil were determined. Within plants, the maximum accumulation of Pb was found in roots while the remaining part of Pb was mainly located in leaves. Pb L-III edge XANES (X-ray Absorption Near Edge Spectroscopy) was applied to identify the principal Pb carrier molecules in the different plant organs. The data suggest that in roots Pb immobilization is mainly due to the complexing ability of histidine, which binds the metal and, to a lesser extent, to precipitation of Pb as carbonate. The transport to the upper plant organs is mainly attributed to Pb complexes with organic acids. In stems and leaves, Pb bonding is mainly carboxylic and amino acid-like, thus confirming the role of these substances in promoting Pb mobility. Thio amino acidic (glutathione and cysteine-like) Pb complexes, which in this study were only found in stems, can also be held responsible for Pb long-distance transport from roots to shoots

Melatonin-induced DNA demethylation of metal transporters and antioxidant genes alleviates lead stress in radish plants

“…Plant roots are considered as the most vulnerable tissue, with a direct correlation with the uptake of HMs from soil solution. It was reported that radish roots and hypocotyls accumulated a large amount of Pb, especially in roots, which accounted for almost 50% of the total lead content of the plant 23 , 24 . Hence, it is of great importance to reduce the Pb content and dissect the molecular mechanism of Pb detoxification in radish.…”

Response of Carrot (Daucus carota L.) to Multi-Contaminated Soil from Historic Mining and Smelting Activities

“…However, the increase in callose content in response to stress generally limits primary root growth [51]. Lead transport from roots to the leaves was immobilised by the formation of Pb complexes with organic acids (carboxylic and amino acids), affecting Pb mobility in plant vessels [52]. Additionally, Pb availability in the roots is affected by the presence of other TEs.…”

The New Beamline LISA at ESRF: Performances and Perspectives for Earth and Environmental Sciences

“…Among the published works based on measurements performed at the beamline in the last few years, we point out the investigation of Tl contamination of the drinkable water from the public distribution system of Valdicastello Carducci-Pietrasanta (northern Tuscany, Italy) [9]; the study of As contamination of floodplain soils and groundwater from shallow aquifers [10,11]; the study of Fe chemical environment in asbestos and erionite mineral fibers [12]; the investigation of selenium (Se) and lead (Pb) accumulation, distribution, and speciation in edible plants [13,14]; the Fe speciation in urban particulate matter and industrial quartz dusts [15,16]; the investigation of amorphous zinc (Zn) biomineralization ("white mud"), occurring at Naracauli stream, Sardinia [17]; the Sb speciation in brake linings, brake pad wear residues, road dust, and atmospheric particulate matter [18]; the interaction of As-rich natural pyrite with aqueous selenite [Se (IV)] [19], and As speciation in travertines [20].…”