Cadmium uptake in above-ground parts of lettuce (Lactuca sativa L.)

Because of its high Cd uptake and translocation, lettuce is often used in Cd contamination studies. However, there is a lack of information on Cd accumulation in the above-ground parts of lettuce during the entire growing season. In this study, a field experiment was carried out in a Cd-contaminated area. Above-ground lettuce parts were sampled, and the Cd content was measured using a flame atomic absorption spectrophotometer (AAS). The results showed that the Cd concentration in the above-ground parts of lettuce increased from 2.70 to 3.62mgkg−1 during the seedling stage, but decreased from 3.62 to 2.40mgkg−1 during organogenesis and from 2.40 to 1.64mgkg−1 during bolting. The mean Cd concentration during the seedling stage was significantly higher than that during organogenesis (a=0.05) and bolting (a=0.01). The Cd accumulation in the above-ground parts of an individual lettuce plant could be described by a sigmoidal curve. Cadmium uptake during organogenesis was highest (80% of the total), whereas that during bolting was only 4.34%. This research further reveals that for Rome lettuce: (1) the highest Cd content of above-ground parts occurred at the end of the seedling phase; (2) the best harvest time with respect to Cd phytoaccumulation is at the end of the organogenesis stage; and (3) the organogenesis stage is the most suitable time to enhance phytoaccumulation efficiency by adjusting the root:shoot ratio. •Cd uptake in lettuce above-ground parts over an entire growth stage were evaluated.•Cd content was highly related to lettuce biomass growth.•Highest Cd concentration in lettuce happened at the end of the seedling stage.•Cd accumulation of an individual lettuce plant could be described by a S curve.•Cd uptake during organogenesis was highest (80% of the total).