Environmental Control and Controlled Elicitation Strategies to Modulate Phytochemical Quality of Medicinal and Aromatic Plants in Controlled Environment Agriculture

Medicinal and aromatic plants are important sources of secondary metabolites used in pharmaceutical, cosmetic, nutraceutical, and health-related applications. However, the phytochemical and bioactive composition of plant raw materials is often highly variable because it is influenced by genotype, developmental stage, cultivation environment, and post-harvest conditions. Controlled environment agriculture (CEA) offers an opportunity to reduce this variability by regulating key aboveground and root-zone factors under reproducible cultivation conditions. This review synthesizes recent research on how environmental control in CEA can influence plant metabolism, biomass formation, phytochemical accumulation, and production value in medicinal and aromatic plants. Particular attention is given to light spectrum and quantity, UV radiation, air temperature, vapor pressure deficit, CO2 concentration, nutrient solution composition, pH, electrical conductivity, root-zone temperature, salinity, and chemical elicitors. The review distinguishes general environmental regulation from controlled elicitation: some factors primarily support growth, resource-use efficiency, and product consistency, whereas others can be applied as defined stimuli to activate stress-related or defense-related secondary metabolism. Evidence indicates that these factors can modify phenolics, flavonoids, terpenoids, alkaloids, essential-oil constituents, and other bioactive compounds. However, reported phytochemical changes should not be evaluated only by metabolite concentration but also by biomass production, resource input, technological feasibility, and batch-to-batch consistency. The review also highlights the need to move from single-factor optimization toward integrated, plant-informed control strategies that account for factor interactions, treatment timing, genotype specificity, non-destructive feedback, and realistic energy and resource constraints. Integrating plant physiology, phytochemistry, environmental control, and production technology may support the development of CEA as a framework for developing phytochemical standardization protocols and more reproducible production of high-value medicinal plant material, although further validation across batches, production cycles, and resource inputs is required.