Photosynthetic parameters and growth of rice, lettuce, sunflower and tomato in an Entisol as affected by soil acidity and bioaccumulation of Ba, Cd, Cu, Ni and Zn

The bioaccumulation of trace elements (TEs) in crops consumed by humans can reduce food production as a consequence of photosynthetic damage in plants and cause several diseases in humans. Liming is a soil management strategy designed to alleviate soil acidity and mitigating these problems by reducing the TE bioavailability. In this study, we evaluated the effect of liming on photosynthesis, growth, and bioaccumulation of barium (Ba), cadmium (Cd), copper (Cu), nickel (Ni), or zinc (Zn) in lettuce (Lactuca sativa L.), rice (Oryza sativa L.), sunflower (Helianthus annuus L.), and tomato (Solanum lycopersicum L.) grown in a sandy Entisol. The crops were grown in either uncontaminated or contaminated Entisol, at two base saturation (BS%) ratios: 30% for all crops or 50% for rice and 70% for lettuce, sunflower, and tomato. The photosynthesis-related parameters varied depending on the metal and the crop, but in general, increasing BS% did not attenuate photosynthetic damage induced by Ba, Cd, Cu, Ni, and Zn in the crops. There was no strong correlation between the photosynthetic parameters and biomass production, which indicates that the suppression of biomass induced by Ba, Cd, Cu, Ni, or Zn is related to other metabolic disorders in addition to the impairment of CO2 assimilation or chlorophyll synthesis in the crops assayed, with the exception of Ni and Zn in lettuce. In conclusion, increasing BS% was not consistent in reducing Ba, Cd, Cu, Ni, and Zn accumulation in the edible parts of lettuce, rice, sunflower, and tomato grown in the sandy soil, which is probably related to the low capacity of this soil to control TE bioavailability.