Aluminum Toxicity

Aluminum is a light metal that makes up 7% of the earth’s crust and is the third most abundant element, after oxygen and silicon, plant roots are therefore almost always exposed to aluminum in some form (Ma et al. 2001). Aluminum exists in soils in many harmless forms, including hydrous oxides, aluminosilicates, sulfates, and phosphates (Haynes and Mokolobate 2001). Aluminum inhibits plant growth by affecting plant roots and development (Delhaize et al. 1993; Ma et al. 2001), inhibiting both cell divisions in the apical root meristem and cell elongation (Blamey et al. 1983). Roots become stubby and brittle; root tips and lateral roots become thick and occasionally necrotic brown (Mossor-Pietraszewska 2001). These effects restrict the ability of the plant to take up nutrients and water, leading to nutrient and/or water stresses (Rout et al. 2001; Haynes and Mokolobate 2001). Plants in acid soil, owing to aluminum solubility at low pH, exhibit a variety of nutrient-deficiency symptoms, with a conse­quent decrease in yield. Aluminum toxicity is linked with phosphorus, calcium, magnesium, or iron deficiency syndrome (Rout et al. 2001). To overcome the lack of productivity in aluminum toxic soil, the first step is to treat acidity, which will promote better root growth and function and will allow nutrients and water to be taken up more effectively by the plant.