Laundry detergents, a mixture of different compounds, are used as washing agents in houses and cleaning agents in institutions and industries. As a result, industrial and domestic wastewater usually contains detergent contamination in variable amount. In many developing countries, untreated municipal and industrial wastewater is used for irrigation of crops. There is a possibility that laundry detergents and their ingredients present in irrigation water may affect plant growth as reported in several plant species. However, studies on the effects of laundry detergents on important cereal crops like maize can rarely be found in literature. Therefore, the present study was conducted to evaluate the effects of two commonly used commercial laundry detergents on germination, root-shoot length, fresh biomass, leaf number, leaf width, cell viability, cell injury, light-harvesting pigments, protein contents, and ion concentration in maize (Zea mays L.) seedlings. The obtained results revealed that both the detergents in the tested concentration range (1-500 mg L-1) did not significantly affect seed germination in maize. Similarly, shoot growth, leaf number, and leaf width were not significantly affected by detergents, while in the case of root, one detergent promoted root growth while the other one inhibited it. Both the detergents caused a slight increase in total soluble proteins, and this effect was significant at the highest tested one or two concentrations of detergents (100 and 500 mg L-1). Chlorophylls a and b and total carotenoids were very sensitive to detergent stress and significantly reduced at detergent concentration above 1 or 10 mg L-1. Both the detergents caused an increased cell leakage and reduced cell viability, and in most cases, this effect was statistically significant at detergent doses above 10 mg L-1. Exposure to detergents caused an increased accumulation of Na+, K+, and Ca2+ in maize seedlings. It can be concluded that detergents present in irrigation water at higher concentrations can adversely affect maize by impairing light-harvesting pigments and cell viability.
Keywords: Cell injury; Cell viability; Chlorophyll; Laundry detergents; Maize; Phytotoxicity.