Potassium/magnesium antagonism : an investigation of its characteristics during uptake, translocation, and physiological functions
The primary cause of the global occurrence of Mg deficiency is the wide potassium (K)/magnesium (Mg) ratios in the soil solution. High K concentrations have been demonstrated to suppress the uptake of Mg. In addition, mounting evidence indicated that K can suppress the translocation and physiological functions of Mg in plants. The current models and working hypotheses do not account for all findings and contradictions regarding this nutrient interaction. Therefore, this thesis aims to investigate the characterization of the exact pattern of K/Mg interaction and evaluate foliar fertilization as an alternative application form under antagonistic conditions. According to the current model, high concentrations of K suppress the uptake of Mg, as both cations are absorbed through non-selective cation channels. The results of this study on oat and maize demonstrated that the suppressive effect of K on Mg uptake is limited. The suppressive effect diminishes with the further increase of the K/Mg ratio. These findings are supported by investigated Mg-specific uptake transporter ZmMGT10, which exhibited higher relative mRNA expression levels in response to elevated K exposure in maize plants. Despite the long-standing recognition of ZmMGT10 as a selective Mg uptake transporter under conditions of deficiency, its role in the K/Mg interaction remained unexplored prior to this study. Furthermore, this thesis on maize and oat demonstrates that elevated levels of K in the root have a synergistic rather than antagonistic effect on Mg translocation, contrary to the previous assumption by the scientific consensus. These findings are additionally supported by the investigation of a Mg-specific translocation transporter (MGR6). Under high K concentrations, this transporter exhibited higher expression levels. Due to the long-term increase in Mg translocation under such high K conditions, it can be inferred that a greater quantity of Mg is translocated via MGR6.
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