| Cadmium (Cd) is one of the most deleterious heavy metals to both plants and animals, and its contamination in soil has turned into one of the most trouble agricultural and environmental issues worldwide. Genetic variation in Cd uptake and tolerance exists between and within plant species. Consequently, it is one of the best cost-effective and efficient approaches to develop Cd-tolerant genotypes with low Cd accumulation in edible parts so as to alleviate health risks associated with Cd exposure and guarantee food safety and make full use of natural resource. Meanwhile, it has been demonstrated that Cd absorption and accumulation in crops is a function of the complex interaction of soil, plant and environmental and farming factors that influence their phyto-availability. It would thus be beneficial to reduce Cd uptake and accumulation in crops by improving agronomic practices. To breed Cd-tolerant genotype or improve agronomic practices, it is important to find out the potential of Cd accumulation in existing genotypes and their physiological responses/mechanism to Cd exposure. However, there is little information about the genotypic difference in Cd tolerance, uptake and accumulation, and which has in some extent limited the developments of its related breeding and cultivation programs to prevent Cd accumulation in plants. This investigation was carried out to study the physiological mechanism of genotypic difference in Cd- uptake, accumulation and tolerance of barley and detrimental effects of Cd on growth and yield formation, based on the research of genotypic variation of kernel Cd concentration and its genotype Location effect, by using four levels of Cd hydroponic experiments. Meanwhile, the possibility of reducing Cd uptake and accumulation in crops by application of chemical regulators were also studied in this investigation. The major results were summarized as follows:1. Genotypic variation in kernel heavy metal concentrations in barley and as affected by soil factorsGenotypic 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 heavymetals, such as Cd and Cr, higher than the maximum permitted concentration (MFC). Soil properties such as pH and EDTA-extractable heavy metal content played an important role in heavy metal uptake and accumulation in barley. Data from the six soils showed that the soil in Ningbo was lower in pH and contained the highest EDTA- Cd, Cu, and Cr, causing significantly higher kernel Cd, Cu and Cr concentrations in barley grains. Kernel Cd, Zn, Cr, Mn and Fe concentrations were closer to EDTA-extractable corresponding metal contents than to soil pH. Significant cultivar effects were identified, but these were less than the site effects. Meanwhile, although Genotype x Location effect existed, genotypes performed consistently across six locations. Therefore, it is important to select suitable cultivars for special regions. Positive relationship between kernel Cd, Zn, Cr and Mn found in this study indicated the potential to screen or develop low heavy metal accumulation cultivars or lines. In addition, regression equations between kernel Cd, Zn, Cr, Mn and Fe concentrations and its EDTA-extractable contents were established and suggested to be used in predicting soil critical levels of these metals for safe barley production.2, Cultivar differences in growth of barley seedlings and their Cd and nutrient uptake under various Cd levelsA hydroponic experiment was carried out to examine genotypic differences of barley in the uptake/accumulation of Cd and some mineral elements, plant development and biomass accumulation under different Cd levels. The results showed that plant height, leaf number, SPAD value and biomass accumulation of shoot/root were significantly reduced in the plant grown in luM Cd nutrient solution compared with control, and the absorption of Zn, Mn and...
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