Effect of gamma irradiation on the uptake, translocation, and phytotoxicity of lead and cadmium in a soil–barley (Hordeum vulgare L.) system

TL;DR

Pre-sowing gamma irradiation of barley seeds (35–150 Gy) increased growth and yield components and reduced Cd and Pb concentrations in grain relative to unirradiated controls, apparently by increasing root accumulation while restricting translocation to aboveground tissues and grain. The authors propose 50–150 Gy as a low-cost seed treatment for mitigating grain metal contamination.

Key findings

• Growth and yield were generally enhanced: at booting, root length rose by 36.18, 24.44, 35.33, 17.99, 26.09, and 20.99% for 35, 50, 75, 90, 120, and 150 Gy, respectively, and the root-shoot ratio was higher than 0 Gy under all doses (35–150 Gy) at every stage measured. Spike length increased 14.34–58.67%, spikelet number 33.33–111.11%, and spikelet grain weight 38.10–137.46% (all doses except 75 Gy, which fell to 0.43 g vs. 0.39 g control).
• Grain Cd fell significantly by 34.62–64.00% at 50, 90, 120, and 150 Gy; grain Pb was below the GB 2762-2022 limit of 0.2 mg/kg under all treatments except 35 Gy. Grain Cd nonetheless exceeded the 0.1 mg/kg permissible limit in all treatments, including controls.
• Metal partitioning shifted toward roots: R-BCFCd exceeded 1 in all treatments and stages, and all irradiation treatments increased root BCF for Cd and Pb (except 120 Gy for Cd) while decreasing stem, leaf, and grain BCF (except 35 Gy in leaf Cd and 50 Gy in L-BCFCd). All irradiation treatments reduced R-S+L-TFCd and R-S+L-TFPb at maturity by 0.04–66.94% and 82.05–94.83%, respectively, with 50 Gy the most pronounced for Pb; S+L-G-TFPb was 0 at 75–150 Gy.
• Pearson correlations at maturity: grain Cd was significantly positively correlated with S-BCFCd, G-BCFCd, and R-S+L-TFCd (S+L-G-TFCd was not significant); grain Pb was significantly positively correlated with G-BCFPb and S+L-G-TFPb.

Methods

• Pot experiment with Cd- and Pb-contaminated field soil (0–20 cm, Xinxiang City, Henan; pH 7.31, total N 43.51 mg/L, total P 29.97 mg/L, Pb 60.0 mg/kg, Cd 17.3 mg/kg) collected near battery production sites. Barley seeds were irradiated with a ⁶⁰Co source at 6.25 Gy/h at doses of 0, 35, 50, 75, 90, 120, and 150 Gy; each treatment was replicated three times, with 20 seeds sown per pot and thinned to 10 plants per pot in 10 kg soil.
• Plants and soil were sampled at tillering, jointing, booting, and maturity. Plant height, root length, root-shoot ratio, and maturity yield components (spike length, grain number, grain weight per spike) were measured; Pb and Cd in digested plant and soil samples were quantified by atomic absorption spectrometry.
• One-way ANOVA with Duncan's multiple range test (SPSS 20.0, p < 0.05) compared treatment means; BCF and TF indices were computed from tissue concentrations and analyzed with Pearson correlation using R's "chart.Correlation."

Limitations

• The paper states no limitations section; no explicit limitations are given in the text.
• Evident from the text: results derive from a single pot experiment on one contaminated soil and one barley genotype, with no field validation, so the authors' recommendation of pre-sowing irradiation as a mitigation strategy is not tested beyond this setting.
• Grain Cd remained above the 0.1 mg/kg permissible limit under every treatment, so the treatment reduced but did not resolve Cd contamination; the proposed mechanisms (modulated physiological responses, altered transport pathways, phytochelatin or secondary metabolite synthesis) are offered as hypotheses without direct molecular or physiological measurements, and the analysis rests on correlation rather than causal evidence.