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

Aims: 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.

Methods: We performed a Mg uptake tracer experiment in rice plants using ²⁸ Mg.

Results: Mg uptake was mediated by high- and low-affinity transport systems. The K_m value of the high-affinity transport system was approximately 70 μM 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.

Conclusions: 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.