The importance of magnesium (Mg) for plant growth is well-documented. Silicon (Si)-mediated alleviation of mineral deficiencies has been also reported in a number of plant species; however, there is no report on the relevance of Si nutrition in plants grown in Mg-deficient condition. Therefore, in the present work, an attempt was undertaken to study the role of Si nutrition in maize plants exposed to Mg deficiency. Plants were grown either under low (0.02 mM) or normal (0.5 mM) levels of Mg, with or without Si supplement. We have shown that Mg-deficient plants treated with Si maintained their growth and increased significantly the levels of chlorophyll and soluble sugars compared to those plants which did not receive Si. In addition, the concentrations of hexose-P, and glycolytic intermediate metabolites-mainly organic acids (isocitric and glutamic acids)-were increased in response to Si nutrition, which was associated with an increase in the levels of stress amino acids such as gamma-aminobutyric-acid (GABA), serine and glycine, as well as polyamines putrescine, which overall contributed to Mg stress tolerance. In addition, Si enhanced the levels of phytohormones cytokinin iso-pentenyladenine (IP), iso-pentenyladenine riboside (IPR), jasmonic acid (JA) and its derivate l-isoleucine (JA-ILE). The increase in cytokinin maintained the growth of Mg-deficient plants, while JA and JA-IEA were induced in response to carbohydrates accumulation. Altogether, our study reveals the vital role of Si under Mg deficiency by regulating plant primary metabolite and hormonal changes.
Keywords: assimilate partitioning; hormonal regulation; mineral deficiency; primary metabolite.