Effects of magnesium deficiency on magnesium uptake activity of rice root, evaluated using 28 Mg as a tracer

The mechanisms underlying magnesium (Mg) uptake by plant roots remain to be fully elucidated. In particular, there is little information about the effects of Mg deficiency on Mg uptake activity. A Mg uptake kinetic study is essential for better understanding the Mg uptake system. We performed a Mg uptake tracer experiment in rice plants using (28) Mg. Mg uptake was mediated by high- and low-affinity transport systems. The K (m) value of the high-affinity transport system was approximately 70 mu M under Mg-deficient conditions. The Mg uptake activity was promoted by Mg deficiency, which in turn fell to the basal level after 5- min of Mg resupply. The induced uptake rate was inhibited by ionophore treatment, suggesting that an energy-dependent uptake system is enhanced by Mg deficiency. The Mg uptake changes rapidly with Mg conditions in rice, as revealed by a (28) Mg tracer experiment. This technique is expected to be applicable for Mg uptake analyses, particularly in mutants or other lines.