The inter-relation between nitrogen availability and cadmium toxicity was studied in roots of barley seedlings with emphasis on the analysis of expression of 10 selected genes relevant for growth in the presence of toxic Cd concentrations. The response to Cd exposure differed quantitatively or qualitatively for the 10 genes in dependence of the N supply. Transcripts of glutathione synthase, glutathione reductase, glutathione peroxidase and dehydroascorbate reductase were measured as parameters involved in antioxidant defence, metallothionein, phosphoenolpyruvate carboxylase and phytochelatin synthase (PCS) were analysed as genes related to heavy metal binding, and vacuolar ATPase subunits VHA-E and VHA-c and a NRAMPtransporter as genes being implicated in Cd transport. Reprogramming of the Cd response was most obvious for PCS and NRAMP whose transcript levels were unaltered and down-regulated, respectively, in the presence of Cd at adequate N, but strongly up-regulated upon Cd exposure under conditions of nitrogen deficiency. Different responses to Cd at varying N supply were also seen for the antioxidant genes. The results on gene expression are discussed in context with the changes in biochemical parameters, and underline the importance of evaluating the general growth conditions of a plant when discussing its specific response to a stressor such as Cd.The sequence of the nramp cDNA was filed at the EMBL/GenBank/DDBJ Databases under the accession number AJ514946.
This paper presents students’ word associations with terms regarding the Wadden Sea. A continuous free word-association method was used in which the students from secondary schools (n = 3119, average age: 13.54 years) reported their associations with the stimulus words Wadden Sea, mudflat hiking tour, and tides in written form. Data were collected from students living close to the Wadden Sea and from students living inland. We performed a quantitative content analysis including the corresponding formation of categories. In addition, students’ school, out-of-school with the class, and private experiences the Wadden Sea ecosystem were recorded. The study shows that not only subject-related concepts should be considered at different levels, but non-subject-related aspects as well. The associations of the inland and non-inland students are statistically significantly different. The Wadden Sea and its biome were found to be completely unknown to some students. Students’ school, out-of-school with the class, and private experiences of the wetlands are also very mixed, regarding their Wadden Sea visitation frequency, and surprisingly cannot be directly derived from their place of residence. This research makes an important contribution towards the design of future biology didactic studies on the Wadden Sea.
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