5-Aminolevulinic Acid (ALA) Reduces Arsenic Toxicity Stress in Wheat (Triticum aestivum L.)

Arsenic (As) is characterized as phytotoxic and belongs to the general stresses which hinder plant growth and productivity. The elimination of As accumulation in wheat grain is a major research goal and having knowledge in physiological grounds for As stress resisting will help to protect plants and human against these toxicities. 5-aminolevulinic acid (ALA) anti-stress material is one of these materials. The present investigation was designed to use ALA in reduction As toxicity of wheat plants. Data indicated that As and/or ALA at the low levels stimulated wheat growth and productivity of wheat plants grown in saline condition. At the high level of As (more than 60 mg/kg soil), toxicity symptoms of As reflected by an inhibition of growth and productivity. The addition of ALA alleviated the symptoms of As toxicity stress (60 mg/kg soil), since wheat growth and productivity had not showed significant reduction at the higher levels of As (80 and 100 mg/kg soil). It was also found that photosynthetic pigments as well as activities of Ascorbate peroxidase (APX), superoxide dismutase (SOD), and peroxidase (POD) were associated with the oxidative damage of the enzymatic defense system caused by the stresses of As toxicity. Phosphorus concentrations in the shoots were increased with an increase in As levels from control (0) till 60 mg/kg soil then decreased from 80 to 100 mg/kg soil and an additive effect was detected with ALA application. As concentration in wheat grain and straw did not exceed the maximum permissible limit for food stuffs (0.1 mg/kg) after ALA treatment, it could be concluded that wheat plants can be cultivated in the contaminated areas with As (60 mg/kg soil) without affecting productivity and yield quality. ALA as an antioxidant would be the best candidate for protection against As toxicity in wheat plants grown under saline condition. Further investigations are needed to understand the mechanisms that influenced wheat growth grown under As toxicity.