Lead effects on sorghum and soybean physiology in oxisols

Lead is a persistent element in soils and has deleterious effects on living organisms. The aim of this study was to investigate the effect of different lead (Pb) concentrations on soybean and sorghum in soils. The experiment was conducted following ISO 11.269–2 guidelines, with samples of a Latossolo Vermelho-Amarelo distrófico (LVAd) and a Latossolo Vermelho distroférrico (LVdf) contaminated with Pb-acetate at increasing concentrations [sorghum (Sorghum bicolor): 0, 200, 400, 800, 1200, 1600, 2200 and 2800 mg kg−1 of dry soil; soybean (Glycine max): 0, 50, 100, 200, 400, 800, 1600, 3200 mg kg−1 of dry soil]. Different variables were measured regarding plant growth and physiological responses. The effect of high Pb concentrations on the physiology of the species studied led to a reduction of up to 80% in SDM. Data from the principal component analysis showed that starch and total soluble sugars were more negatively affected by Pb in the soil, while antioxidant system enzymes showed a significant increase. In an overall evaluation, sorghum is physiologically more resistant to Pb contamination than soybean, as observed from less severe damage in the variables concerning vegetative growth, physiological responses and carbohydrate metabolism.