Magnesium Plus Hydrogen Fertilization Enhances Mg Uptake, Growth Performance and Monoterpenoid Indole Alkaloid Biosynthesis in Catharanthus roseus

Magnesium and hydrogen fertilization have been reported to contribute to plant growth and metabolite production. Simultaneous fertilization of magnesium and hydrogen is a promising strategy for plant development and secondary metabolism, but remains unexplored in <i>Catharanthus roseus</i> (L.) G.Don, which produces varieties of monoterpenoid indole alkaloids (MIAs). This study conducted a glasshouse experiment comprising five treatments: MgO, MgSO₄, MgH₂, magnesium powder (MgP), and the control, to investigate and compare the effects of Mg fertilizers and Mg plus H₂ fertilizers on soil pH, Mg uptake, seed germination, plant growth, and MIA biosynthesis in <i>C. roseus</i>. Application of MgH₂, MgP, and MgO fertilizers significantly raised soil pH to 6.14~6.38. MgH₂ and MgP fertilization significantly increased plant weight by 60% and 29% over the control, respectively. MgH₂ and MgP produced greater increases in Mg content, chlorophyll content, plant height, and weight than MgO and MgSO₄. Four fertilizers up-regulated the expression of most MIA biosynthetic genes, especially those in the vindoline pathway. Among them, MgH₂ yielded the highest contents of catharanthine, vindoline, and ajmalicine, reaching 167%, 149% and 517% of the control, respectively. Pearson correlation analysis showed significant positive correlations among H₂ release, soil pH, and Mg uptake, as well as with plant growth and MIA content. These findings suggest that Mg plus H₂ fertilizers released H₂ and increased soil pH to promote Mg uptake, chlorophyll contents, plant growth, and MIA production in <i>C. roseus</i>, highlighting the potential of MgH₂ and Mg powder as innovative fertilizers to enhance alkaloid yields in medicinal plants.