Effects of different concentrations of lead on some biochemical and physiological parameters of rice (Oryza sativa L.)

Lead (Pb) not only negatively alters plant growth and yield but may also have potentially toxic risks to human health. In the present study, the effects of different concentrations of Pb (150 and 300 μM) on growth, physiological and biochemical attributes of rice under hydroponic conditions were investigated. The results showed that Pb treatments with negative effects on chlorophyll metabolism reduced photosynthetic pigments and, consequently, diminished the growth and biomass of rice plants. Pb stress induced oxidative stress and damage to bio-membranes by increasing the accumulation of hydrogen peroxide and methylglyoxal. The activity of antioxidant enzymes and glyoxalase cycle was upregulated in rice leaves under Pb toxicity. Pb treatments altered the levels of non-enzymatic antioxidant compounds (glutathione (GSH) and ascorbic acid (ASA)) in the leaves of rice plants by reducing the ratios of reduced ASA to oxidized ASA and reduced GSH to oxidized GSH compared to control plants. Therefore, concentrations of 150 and 300 μM Pb in the soil can induce negative effects on important physiological and metabolic processes of rice, which reduce plant growth and biomass.