Bioavailability, Accumulation and Distribution of Toxic Metals (As, Cd, Ni and Pb) and Their Impact on Sinapis alba Plant Nutrient Metabolism

Abstract

This study presents the behavior of white mustard seedlings Sinapis alba grown for three months in laboratory polluted soil containing As, Cd, Ni and Pb. Four different experiments were performed in which As was combined with the other three toxic metals in different combinations (As, AsCd, AsCdNi, AsCdNiPb), keeping the same concentrations of As and Cd in all tests and following the national soil quality regulations. The effects of these metals were monitored by the analytical control of metal concentrations in soil and plants, bioavailability tests of mobile metal fractions using three different extracting solutions (DTPA + TEA + CaCl2-DTPA, DTPA + CaCl2-CAT, and CH3COONH4 + EDTA-EDTA) and calculation of bioaccumulation and translocation factors. Additionally, micro, and macro-nutrients both in soil and plant (root, stem, leaves, flowers and seeds) were analyzed in order to evaluate the impact of toxic metals on plant nutrient metabolism. Metals were significantly and differently accumulated in the plant tissues, especially under AsCdNi and AsCdNiPb treatments. Significant differences (p < 0.05) in the concentration of both As and Cd were highlighted. Translocation could be influenced by the presence of other toxic metals, such as Cd, but also of essential metals, through the competition and antagonism processes existing in plant tissues. Significantly, more Cd and Ni levels were detected in leaves and flowers. Cd was also detected in seeds above the WHO limit, but the results are not statistically significant (p > 0.05). The extraction of metallic nutrients (Zn, Cu, Mn, Ni, Mg, K, Fe, Ca, Cr) in the plant was not influenced by the presence of toxic metal combinations, on the contrary, their translocation was more efficient in the aerial parts of the plants. No phytotoxic effects were recorded during the exposure period. The most efficient methods of metal extraction from soil were for As-CAT; Cd-all methods; Pb and Ni-DTPA. The Pearson correlations (r) between applied extraction methods and metal detection in plants showed positive correlations for all toxic metals as follows: As-CAT > DTPA > EDTA, Cd-DTPA > CAT > EDTA, Ni-EDTA = DTPA > CAT, Pb-EDTA = DTPA = CAT). The results revealed that Sinapis alba has a good ability to accumulate the most bioavailable metals Cd and Ni, to stabilize As at the root level and to block Pb in soil.

Transcriptomics, proteomics, and metabolomics interventions prompt crop improvement against metal(loid) toxicity

“…Consequently, omics methodologies have become crucial in unraveling the biological interactions and molecular pathways that enhance metal(loid) tolerance. While genomics-assisted breeding has made significant strides (Varshney et al 2018 , 2021 ), exploring other omics tools (transcriptomics, proteomics, and metabolomics) is important to improve our molecular understanding (Fig. 3 ).…”

“…Machine learning (ML) techniques are used for genomic prediction, selection, and marker-assisted breeding (Harfouche et al 2019 ; Esposito et al 2019 ; Pazhamala et al 2021 ; Varshney et al 2021 ; Jung et al 2021 ; Khan et al 2022 ). Plant breeders use AI tools like ML, deep learning, and predictive analysis to understand plant behaviors under various conditions, including metal(loid) toxicity (Esposito et al 2019 ; Yan and Wang 2023 ; Tripodi et al 2022 ).…”

Bioavailability of Metals in the Biosphere

“…Once metals have passed through these stages and accumulated in plants, they become available to the local population and herbivores immediately or through the food pyramid. The entry of food pyramid elements is often limited by the movement from the soil to the plant root (Hussain et al, 2021;Vasile et al, 2021;Chen et al, 2022). This crucial step stands heavily influenced by the elements levels in earth orifice mixture that, in turn, are measured by several confined ground properties, including acidity index, water content, humidity, redox potential, and other criteria.…”

Heavy Metal Contamination in Soil: Implications for Crop Resilience and Abiotic Stress Management

“…Toxic metals/metalloids can compete with essential nutrients for plant uptake, leading to deficiencies and disrupting plant growth and metabolism. For instance, Cd can interfere with the uptake of Zn and calcium (Ca), while Pb can inhibit the uptake of potassium (K) [100][101][102]. This competition occurs because toxic metals/metalloids can mimic essential nutrients, leading to their uptake by the same transporters or interfering with the transport process [100].…”

“…Cd is known to have a chemical similarity to Zn, which leads to competitive uptake and can affect the translocation of essential metals, such as Zn and Mn, within the plant [100]. The presence of Cd can also influence the uptake of Fe and Mg, which are critical for chlorophyll synthesis and photosynthesis [101].…”