Application of ²⁸Mg for characterization of Mg uptake in rice seedling under different pH conditions

Abstract

The magnesium (Mg) uptake of rice seedlings treated with different pH solutions was investigated using tracer of ²⁸Mg. The application of ²⁸Mg enabled the determination of Mg uptake amount within 15 min of the different pH treatments. The uptake amount of ²⁸Mg and its distribution in rice plants were determined by using the imaging plate. The result demonstrated that the Mg uptake amount was approximately 3 μmol/15 min per plant in 0.27 mM Mg solution at pH 5.6, and this uptake decreased by 30 % at lower pH conditions (pH 4.5). On the contrary, the pH 6.5 condition induced the Mg uptake activity to 4.4 μmol/15 min. The inverse relationship found between proton concentration in nutrient solution and the Mg uptake amount within 15 min of treatment demonstrated that the low pH condition could inhibit the Mg uptake activity as a consequence of the competition between Mg²⁺ and proton. It is concluded that under low pH conditions, regardless of other factors, there is a decrease of Mg uptake activity in rice roots.