Strontium Uptake and Effect in Lettuce and Radish Cultivated Under Hydroponic Conditions

The accumulation of strontium (Sr) in lettuce and radish under 0 (control), 0.5, 1, 2.5, 5, and 10 mM Sr treatments in hydroponic solution at 16, 23 and 30 days and the effects of Sr stress on six nutrient elements in plants were investigated. The results showed that Sr concentrations in plant aerial and underground parts increased in low-Sr treatments (0.5, 1 and 2.5 mM) and fluctuated in high-Sr treatments (5 and 10 mM) throughout the three sampling periods. Sr concentrations were higher in roots than in leaves, reaching 108.8 ± 14.7 and 134.1 ± 1.2 mg/g in lettuce and radish roots, respectively, after 10 mM Sr treatment. Translocation factor (TF) values (ratio of the Sr concentrations in aerial parts to that in roots) were inversely related to the Sr content in the hydroponic solution, and reached 1.45 ± 0.17 to 0.15 ± 0.03 and 1.06 ± 0.20 to 0.12 ± 0.004 for lettuce and radish. The variation in chlorophyll content was consistent with that in plant biomass.