Effects of selenium on growth parameters of tomato and basil under fertigation management

Tomato ‘Abigail’ (Solanum lycopersicum L.) and basil ‘Perry’ (Ocimum basilicum L.)were selected asmodel plants for selenium(Se) supplementation to evaluate a) effects of Se concentration in nutrient solution on Se content in different organs under fertigation, b) Se phytotoxicity threshold values, and c) mechanisms.Plants grown in a glasshouse were irrigated with 0, 1, 2, 5, and 10 mg Se/L in the first experiment, while with 0, 0.25, 0.5, 0.75, 1.0, and 1.5 mg Se/L in the second.Tomato plants accumulated Se linearly with rising Se concentrations, whereas accumulation in basil followed a saturation curve.Plants supplemented with 1.5 mg Se/L in the irrigation water accumulated 0.23 and 0.88 mg Se/g dry weight (DW) in tomato fruits and basil shoots, respectively.However, tomato roots, shoots and fruits DWwere 56%, 36%, and 66%lower than in controls, respectively, and basil roots and shoots DW were 92% and 88% lower than in control, respectively.Calculated toxicity-threshold values were 1.27 mg Se/L for tomato and 0.44 mg Se/L for basil.Tomato crops were more tolerant than basil crops, although data suggested yield reduction at lower Se concentrations than those effecting biomass reductions.The results indicate that Se supplementation through drip irrigation may efficiently fortify tomato and basil.However, Se concentrations should be lower than 0.75 and 0.25 mg·L^-1 for tomato and basil, respectively, to avoid yield reduction and possible Se phytotoxicity.