Nutritional and biochemical changes induced by lead in sunflower (Helianthus annuus L.)

Abstract

The aim of this study was to evaluate the effects of increasing concentrations of lead (Pb) in the nutrient solution on growth and macronutrient and organic solute contents of Helianthus annuus plants. The experimental design was completely randomized with four replications. The dry mass yield was not affected by the treatments up to a Pb concentration of 0.6 mM, indicating that H. annuus was tolerant to this Pb concentration in the growth medium. The reductions in leaf, stem and root dry masses at a Pb concentration of 0.8 mM were 74, 84 and 85%, respectively. Lead stress did not reduce the levels of nitrogen (N), phosphorus (P) and potassium (K), indicating that the growth reduction observed at 0.8 mM Pb could not be attributed to deficiencies of these nutrients. On the other hand, Pb significantly reduced calcium (Ca) and magnesium (Mg) contents in leaves, stems and roots, which might, at least in part, explain the Pb-induced growth reduction in the H. annuus plants. Pb increased soluble carbohydrate, free amino acid and proline contents in leaves, and soluble protein and proline contents in roots, showing stress-induced changes in cell metabolism. The data also suggest that Ca and Mg concentrations may be used as nutritional indicators and the proline content may be used as a biochemical indicator of Pb toxicity in H. annuus.

Molecular and biochemical characterization of oxidative stress in tomato plants cultivated with lead (Pb)

“…In the treatments analyzed, no significant differences were found in the leaves in terms of total protein content, but in the stem the highest concentration (100 mg kg -1 ) was significantly higher than the control in 135.1% and that the treatment with 50 mg kg -1 of PbAc 2 (136.59%), causing a significant decrease in the variable analyzed in both treatments (0 and 50 mg kg -1 of PbAc 2 ) (Figure 4A & 4B). This increase in the content of total soluble proteins in the maximum concentration of PbAc 2 used could be due to a saturation in the mechanisms of retention of Pb in the stem, and consequently the finite capacity of this organ to act as a reservoir of the metal, 14 which continues to the leaves, where, although without significant differences, the protein content decreased at the maximum concentration tested. The activity of the GR in the presence of different concentrations of PbAc 2 shows an increase in both parts of the analyzed plant being significant in the leaves (Figure 5A & 5B).…”

Physiological, nutritional, and biochemical indicators of lead tolerance in sunflower genotypes

“…The second experiment was conducted in a factorial arrangement with three sunflower genotypes × two levels of lead (0 and 0.65 mM). This level of lead was based on recommendation of Abreu et al (2016), who indicated that sunflower tolerates Pb up to this level and the soil contamination with Pb usually does not exceed this limit. The genotypes were seeded in 200 mL plastic cups, using washed sand as substrate, and daily irrigated with distilled water.…”

“…As the increase in these compounds was observed only in the roots of Pb-sensitive genotypes, the results suggest that the energy cost for osmoregulation through the synthesis of the organic compounds was higher in the H251 and AG963 genotypes than in the BRS-G27. Changes in the concentrations of carbohydrates and amino acids also evidence Pb-induced disturbances in cell metabolism (Abreu et al, 2016).…”

“…In plants, stress responses vary widely depending on species, toxic elements, duration of the exposure and environmental conditions (Bassegio et al, 2020;Dalyan et al, 2020). In the case of Pb, the most common symptoms of toxicity include reduction of photosynthetic pigments, loss of membrane integrity, reduction of enzyme and photosynthetic activities, disruption of hormonal, ion, and water homeostasis, root browning, and nutritional disorders, inhibition in seed germination, leading to reduced plant growth (Hussain et al, 2013;Abreu et al, 2016;Bassegio et al, 2020;Dalyan et al, 2020).…”

“…Despite the diversity of metals in the soil, Pb uptake by plants depends mainly on its bioavailable fraction (Kim et al, 2015) in the form of divalent cation (Pb 2+ ) and the uptake by passive mechanism (Kabata-Pendias, 2010). Some authors have reported Pbinduced changes in the physiological and biochemical parameters of plants (Abreu et al, 2016;Song et al, 2020). However, responses related to plant growth, accumulation of nutrients and organic solutes, and the Pb distribution in the different organs directly depend on the genotypic characteristics and the Pb concentration in the root environment (Ashraf et al, 2020).…”