Uptake and distribution of selenium in tomato plants as affected by genotype and sulphate supply

Aim of this work was to investigate if the variation among tomato genotypes in selenium (Se) uptake and accumulation observed in short term experiments are maintained over longer growth periods and if there is a positive correlation in shoot between sulphur (S) accumulation and Se accumulation across different genotypes or if higher tissue S results in greater feedback inhibition of Se uptake. Two experiments were carried out under greenhouse conditions and different genotypes of Lycopersicon lycopersicum (UC82B and LA2711), Lycopersicon pennellii (LA716) and Lycopersicon peruvianum (LA2157) were grown until fruit ripening. The results obtained in the two experiments confirmed that sulphate in the growth solution reduced selenate uptake by plants and increased the S content of the leaves. Under low sulphate treatment there was a clear correlation (R(2) = 0.82) between leaf S content and shoot Se content across genotypes in both experiments, indicating that the overall activity of the S transport systems also determines Se transport. Selenium was translocated from shoot to fruit, but the edible portion of the plant contained much less total Se than the inedible plant parts. The difference in Se content between the low and the high sulphate treatments was significantly higher in shoot than in root, confirming that the Se translocation from root to shoot is probably more affected by high sulphate supply than Se uptake by root. In the first experiment the genotype LA716 showed an higher Se accumulation together with higher S content in leaves, indicating a marked ability of this genotype to absorb ions from substrate. In the second experiment UC82B appeared to be more capable to accumulate Se and S rather than LA2711 and LA2157. In both experiments Lycopersicon peruvianum appeared to be less affected by the high concentration of ions in the growth solution and to be able to reduce ion uptake than Lycopersicon lycopersicum and Lycopersicon pennellii.