Impact of Excess Magnesium Salt Supply on Rice Yield, Physiological Response, and Grain Mineral Content

Magnesium nutrition in plants has remained largely unexplored compared to other essential elements. Although the impact of magnesium deficiency on plants has been reported from numerous studies, the responses of plants to excess magnesium salt levels have received less attention. Using five different magnesium levels (0, 500, 1000, 1500, and 2000 ppm) and two magnesium sources (MgSO4 and MgCl2), this study evaluated the effect of excess magnesium salts on rice production and associated physiological processes on a hybrid rice cultivar ‘XP 753’. Rice morphological and physiological parameters, including plant growth, biomass, root morphological features, tissue and grain mineral concentrations, membrane injury (MI), chlorophyll, malondialdehyde (MDA) concentrations, proline concentrations, as well as gas exchange parameters, were evaluated. A dose-dependent reduction in above- and below-ground shoot and root morphological features was observed under the application of magnesium salts on the soil substrate. Analysis of physiological parameters demonstrated that an inhibition in plant growth, biomass, and yield was due to the decrease in total chlorophyll content, net photosynthesis rate, and membrane stability in rice. Furthermore, this study showed that the application of magnesium salts to soil interfered with the uptake and translocation of minerals and significantly increased reactive oxygen species (ROS), malondialdehyde (MDA), and proline levels, indicating the toxic effects of excess magnesium salts on rice plants.