Measuring tomato seed germination on a medium containing either arsenite or arsenate showed that the presence of 0.5 mM NaH2AsO4·7H2O reduced germination by between 20% and 40%, depending on cultivar. The inhibitory effect was mitigated by the addition of CaSiO3. However, the presence of both forms of As had a drastic negative effect on seedling shoot elongation, which was not mitigated by the presence of CaSiO3. In a subsequent soil-based pot trial, damage due to the presence of As was visible by 15 days after the initiation of the treatment, and the provision of CaSiO3 was significantly ameliorative; again, the severity of the effects was cultivar-dependent. Analysis of the accumulation and distribution of As showed that some of the cultivars are As excluders, and others accumulators. As was taken up by the latter cultivars whether or not CaSiO3 supplementation was provided. The extent of As entry into the fruit varied from cultivar to cultivar, but never rose above the safety threshold. A survey of stress response-associated genes showed that LeGR was strongly up-regulated by exposure to As.
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