Foliar Magnesium supply increases the abundance of RuBisCO of Mg-deficient maize plants

Magnesium is a vital macronutrient for plants and is involved in a series of essential physiological processes, e.g., carbohydrate partitioning and photosynthesis. The latter is strictly Mg-dependent, as Mg is the central atom of chlorophyll, and is also required for the de novo synthesis of sugars; this pathway revolves around the activity of the enzyme RuBisCO. When plants are subject to Mg limiting conditions, development as well as yield is reduced. The foliar resupply of Mg, contrary to traditional resupply to the roots, has the advantage of delivering the element directly to the site of highest physiological demand. Thus, the aim of this research is to compare the effects of both resupply methods on the physiology and nutritional status of Mg-deficient plants to see whether foliar application compared to root fertilization can properly improve plant growth after Mg deficiency conditions.Maize plants were cultivated in hydroponics in order to set up a Mg deficient root environment. MgSO4 was then resupplied alternatively to the leaves or to the root. Under Mg-limiting conditions, RuBisCO abundance, as well as the total content of Mn, Zn, Fe, and Cu were severely reduced. This state was significantly ameliorated by the foliar resupply of MgSO4, although the highest increase in biomass production was observed in response to root resupply. The foliar resupply of MgSO4 upregulated the process of photosynthesis in Mg-deprived plants. In this context, the foliar MgSO4 application was able to return RuBisCO abundance to control levels in Mg-deficient plants