Unveiling Sulfur Deficiency-Induced Biochemical Alterations in Medicinal Plants: A Comparative Hydroponic Study on Metabolic Responses in Ocimum citriodorum Vis. and Mentha suaveolens Ehrh.

Sulfur plays a central role in plant metabolism, participating in the formation of numerous essential compounds such as cysteine, methionine, proteins, coenzymes, vitamins, secondary metabolites, and various pigments. In this study, we examined how sulfur limitation affects two Lamiaceae species: lemon basil (Ocimum citriodorum Vis.) and apple mint (Mentha suaveolens Ehrh.). Plants were grown hydroponically under controlled greenhouse conditions and supplied with three sulfur concentrations (1.0, 0.18, and 0.06 mM) for 8 weeks. Our results revealed that sulfur deficiency caused a significant decrease in protein content (up to 80%) while soluble sugars increased by nearly 74%. We also noted a clear reduction in chlorophyll content and biomass. These findings highlight the strong effect of sulfur availability on primary metabolism and confirm its essential role in maintaining the biochemical functions that ensure the health and quality of aromatic and medicinal plants. Further studies should explore secondary metabolite profiles and recovery responses to sulfur resupply.