Influence of Fe0 nanoparticles, magnetite Fe3O4 nanoparticles, and iron (II) sulfate (FeSO4) solutions on the content of photosynthetic pigments in Triticum vulgare

Seeds and seedlings of soft wheat (Triticum vulgare Vill.) were used to study seed germination, leaf elongation, and the content of photosynthetic pigments (chlorophylls a, b and carotenoids) as affected by five concentrations of iron-containing nanoparticles (NP): spherical Fe0 NP with the diameter of 80 ± 5 nm and the magnetite Fe3O4 NP measuring 50–80 nm in width and 4–10 nm in height. The effects of FeSO4 solutions were also tested for comparison. The parameters examined varied as a function of the exogenous agent applied, the agent concentration, and the exposure duration. The highest sensitivity of seedlings was observed in the presence of increasing concentrations of iron (II) sulfate in the nutrient medium. This was evident from the decrease in seed germination percentage, inhibition of leaf growth, and the diminished content of photosynthetic pigments. The apparent toxicity of iron nanoforms varied depending on the parameter examined. (1) The strongest inhibition of germination was exerted by Fe0 NP (toxicity assessed from germination percentage was 3.3% higher with Fe0 NP than with magnetite NP); (2) the inhibition of leaf elongation on the 4th day after germination was most evident in the presence of Fe0 NP (a 12% stronger inhibition in the presence of Fe0 NP than in the presence of magnetite NP), whereas on the 7th day the inhibition was most pronounced with magnetite NP (a 9% stronger inhibition in the presence of Fe3SO4 NP than in the presence of Fe0 NP); (3) the lowest total content of photosynthetic pigments on the 4th day of seedling growth was noted in the presence of magnetite NP (8% lower in the presence of Fe3SO4 NP than in the presence of Fe0 NP), whereas on the 7th day the lowest pigment pool was observed in the presence Fe0 NP (a 3% reduction compared to that in the presence of magnetite NP). The highest content of photosynthetic pigments was recorded in the presence of 0.125 and 0.001 g/L of Fe0 NP, 0.5 g/L and 1 μg/L of Fe3O4 NP, and 1 mg/L FeSO4.