Elicitor-Induced Modulation of Biomass, Antioxidant Enzyme Activities, and Phenolic Profiles in Adventitious Root Cultures of Gypsophila paniculata

Elicitation is a powerful strategy for increasing bioactive metabolites in plant systems. This study is among the first to integrate growth responses, antioxidant enzyme activities, and metabolite profiling in G. paniculata adventitious roots (ARs). The study aims to evaluate the effects of yeast extract (YE) and salicylic acid (SA) on biomass traits, antioxidant enzymes (peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase), and phenolic metabolite profiles. ARs were exposed to YE (0.25–2 g L−1) and SA (50–400 µM) for 28 days. Yeast extract significantly enhanced antioxidant capacity by promoting enzyme activities, phenolics, and flavonoids. In contrast, SA exhibited concentration-dependent effects. Moderate concentrations improved antioxidant activity, while higher concentrations promoted the accumulation of specific flavonoids. Maximum biomass production was achieved with 1 g L−1 YE, which also resulted in the highest metabolite productivity. Conversely, SA treatments caused a progressive reduction in biomass with increasing concentration, although they enhanced the accumulation of selected bioactive compounds. Notably, 100 µM SA resulted in the highest phenolic content and antioxidant activity, whereas 400 µM SA markedly increased flavonoids such as rutin and quercetin. HPLC analysis identified seventeen phenolic compounds, demonstrating that YE acts as a broad-spectrum elicitor, whereas SA functions as a selective metabolic modulator. The differential enzymatic responses further highlight elicitor-specific regulatory patterns in antioxidant defense and secondary metabolism. Overall, these findings demonstrate that elicitor type and concentration differentially influence the balance between growth and secondary metabolism, providing a framework for optimizing metabolite production in controlled in-vitro systems.