Phosphite and Phosphate Have Contrasting Effects on Nutrient Status of Plants

A comprehensive knowledge of the factors underlying the performance of plants under phosphite (Phi) nutrition is critical for its rational use in agriculture. Therefore, the effects of Phi on nutrient status of plants were evaluated by growing oat (Avena sativa) for 60 days in nutrient solutions containing three P treatments: 0.5 mmol L-1 of phosphate (Pi sufficient, Pi-S), 0.05 mmol L-1 of Pi (Pi deficient, Pi-D), and 0.5 mmol L-1 of Phi. In comparison with Pi-S, the Phi impaired plant growth in a more pronounced manner than Pi-D, suggesting toxic effects. Phi plants did not show any variation in N, P, and Ca concentrations in the shoot, but there were reductions in the concentrations of Mg and S and increased concentrations of K, B, Mn, and Zn compared with Pi-S plants. In the root, the Phi decreased the concentrations of P, Ca, Mg, S, and B but increased N, K, Fe, and Mn. In conclusion, Phi and Pi had distinct influence on nutrient status of oat, which contributes to explaining the contrasting performance of plants under Pi or Phi nutrition. These results might also suggest the need for a differential nutritional management in plants under frequent Phi applications.