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

Abstract

The bioaccumulation of trace elements (TEs) in crops consumed by humans can lead to a lower food production due to photosynthetic damages and several diseases in humans, but decreasing soil acidity could mitigate these problems by decreasing TEs bioavailability. Thus, we evaluate the effect of increasing soil base saturation (BS%) 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 sandy Entisol. The crops were grown in uncontaminated or contaminated Entisol, under two 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 crop, but in general, increasing BS% did not attenuate photosynthetic damages induced by Ba, Cd, Cu, Ni and Zn in the crops. There was no strong correlation between the photosynthetic parameters measured and biomass production, which suggest us that the suppression on biomass induced by Ba, Cd, Cu, Ni or Zn is related to other metabolic disorders besides the impairment on CO2 assimilation or chlorophyll synthesis in the crops assayed, with exception of Ni and Zn in lettuce. In conclusion, increasing BS% was not consistent in decreasing Ba, Cd, Cu, Ni and Zn accumulation in the edible parts of lettuce, rice, sunflower and tomato grown in the sandy soil, which probably is related to the low capacity of this soil in control TEs bioavailability.