Genotypic variation in kernel heavy metal concentrations was studied for barley cultivars grown in six locations of Zhejiang, China. These sites covered a wide range of soil and climate. The results showed that barley kernels produced at some sites contained heavy metals higher than MPC. Significant cultivar effects were identified, but these were less than the site effects. Although Genotype

A solution culture experiment was carried out in a greenhouse to study genotypic differences in the effect of cadmium (Cd) on biomass, root and shoot growth of barley during ontogenesis, by using four cultivars and four Cd levels. Barley (Hordeum vulgare L) plants exposed to 0.1μM Cd showed little difference (p>0.05), compared with control, in growth parameters and biomass accumulation during the first 30 days of Cd exposure, and a slight increase in the later days. Exposure to 1μM Cd induced a significant decrease and the deleterious effect became diminished with extended exposure of time, which may be attributed to an adaptation to Cd toxicity occurring during ontogenesis. Increasing Cd concentration in the medium to 5μM caused a sharp decline (p≤0.05) in all measurements and the deleterious effect of Cd became more obvious with extended exposure of time. There was a significant difference among 4 cultivars in the reduction of these parameters caused by Cd oxicity.Zhenong 1 and Wumaoliuling were the least and most affected, respectively. In addition, the difference among genotypes in their response to Cd toxicity basically remained consistent throughout the growth period.

A hydroponic experiment was carried out to study the genotypic di.erence in subcellular distribution and chemical form of Cd and Zn uptake and their interaction in four barley genotypes. Increased Cd level in the medium caused a signi.cant increase of Cd concentration in all fractions of oots/shoots, with most accumulation in FI (cell wall) and FIV (soluble). In root, the greatest amount of Cd was found in extraction solution of 2% HAC or 0.6M HCl, followed by 1M NaCl (20%), and lowest in xtraction of 80% ethanol or d-H2O. While in shoot, the highest value of Cd accumulation was recorded in the fractions extracted by 1 M NaCl and 2% HAC, followed by 0.6M HCl or d-H2O, and least in 80% ethanol extraction solution. There was a distinct di.erence among genotypes in Cd concentration in subcellular and chemical forms and it was found that the Cd-sensitive genotype Wumaoliuling, in comparison with the other three Cd-resistant genotypes, had higher Cd concentration in chloroplast-shoot/trophoplast-root (FII), membrane and organelle (FIII) and in inorganic and water-soluble Cd of roots, while lower in FI, FIV and pectates/protein integrated Cd. After 48h of Cd treatment, the plants were replaced into Cd-free nutrient solution and grown for 72h, a signi.cant decrease in Cd concentration of root FI was observed, with less Cd reduction in Wumaoliuling. In comparison with control (no Cd), addition of Cd signi.cantly increased Zn accumulation in chloroplast (FII), with least increase in Wumaoliuling. The Zn content in the other 3 fractions decreased signi.cantly with addition of Cd, especially in roots, while Wumaoliuling was the most severely a.ected genotype. Moreover, it could be suggested Zn supplement could signi.cantly reduce Cd concentration in root trophoplast and in shoot soluble fraction of Cd-treated plants. 2005 Published by Elsevier Ltd.

Hydroponic experiment was carried out to study the effect of three Cd levels on glutathione (GSH), free amino acids (FAA), and ascorbic acid (ASA) concentration in the different tissues of 2 barley cultivars with di erent Cd tolerance. Cadmium concentration in both roots and shoots increased with external Cd level, while biomass and ASA concentration declined, and Wumaoliuling, a Cd-sensitive genotype was more affected than ZAU 3, a Cd-tolerant genotype. The effect of Cd on GSH concentration was dose- and time-dependent. In the 5d exposure, root GSH concentration increased in 0.5μM Cd treatment compared with control, but decreased significantly in 5μM Cd treatment, irrespective of genotypes. However, in the 10d exposure, GSH concentration in all plant tissues decreased with increasing Cd levels in the culture medium, and Wumaoliuling was much more affected than ZAU 3. Cadmium treatment greatly altered FAA concentration and composition in plants. The effect of Cd on glutathione (Glu) concentration in roots varied with genotypes. ZAU 3 showed a steady increase in root Glu concentration in both 0.5 and 5μM Cd treatments, while Wumaoliuling was decreased by 38.0% in 5μM Cd treatment, compared with the control. The results indicate that GSH and ASA are attributed to Cd tolerance in barley plants, and the relative less reduction in GSH concentration in ZAU 3 under Cd stress relative to the control may account for its higher Cd tolerance.

Effect of cadmium (Cd) on biomass accumulation and physiological activity and alleviation of Cd-oxicity by application of zinc (Zn) and ascorbic acid in barley was studied, using semisolid medium culture including 15 treatments [four Cd concentration treatments: 0.1, 1, 5, 50μmolL-1, four treatments with addition of 300μmolL-1 Zn or 250mgL-1 ascorbic acid (ASA) based on these four Cd concentrations, respectively, and three controls: basic nutrient medium, and with Zn or ASA, respectively]. Cadmium addition to semisolid medium, at a concentration of 1, 5, and 50μmolL-1, inhibited biomass accumulation and increased malondialdehyde (MDA) content of barley plants, while the addition of 0.1μmolL-1 Cd increased slightly dry mass. There was a tendency to a decrease in Zn, copper (Cu) concentrations both in shoots and roots and iron (Fe) inshoots of barley plants exposed to 1 to 50μmolL-1 Cd. In addition, there were indications of a stress repose characterized by increased superoxide dismutase (SOD) and peroxidase (POD) activities relative to plants not ubjected to Cd. The physiological changes caused by Cd toxicity could be alleviated to different extent by application of 300μmolL-1 Zn or 250μmgL-1 ASA in Cd stressed plants. The most pronounced effects of adding Zn or ASA in Cd stressed medium were expressed in the decreased MDA and increased biomass accumulation, e.g., MDA contents were reduced (p≤0.01) by 4.8%-17.8% in shoots and 0.5%-19.7% in roots by adding 300μmolL-1 Zn, in 50mmolL-1 Cd stressed plants, and by 1.3%-7.4% in shoots of barley plants exposed to 1 to 50μmolL-1 Cd. In addition, there were indications of a stress repose characterized by increased superoxide dismutase (SOD) and peroxidase (POD) activities relative to plants not subjected to Cd. The physiological changes caused by Cd toxicity could be alleviated to different extent by application of 300μmolL-1 Zn or 250μmolL-1 ASA in Cd stressed plants. The most pronounced effects of adding Zn or ASA in Cd stressed medium were expressed in the decreased MDA and increased biomass accumulation, e.g., MDA contents were reduced (p≤0.01) by 4.8%-17.8% in shoots and 0.5%-19.7% in roots by adding 300μmolL-1 Zn, in 50μmolL-1 Cd stressed plants, and by 1.3%-7.4% in shoots and 2.6%-4.5% in roots by application of 250μmolL-1 ASA, respectively. However, ASA addition may enhance Cd translation from root to shoot, accordingly, ASA would be unsuitable for the edible crops grown in Cd contaminated soils to alleviate phytotoxicity of Cd.