**4. Conclusions**

The current review deciphers the role of light as a promising elicitor in enhancing the production of key metabolites in different in vitro systems of plants. Among various abiotic elicitors, light has gained attention in enhancing secondary metabolite production due to its specified wavelengths, cost-effectiveness, and durability. A plethora of studies have reported the effect and quality of different types of light sources on enhanced secondary metabolite accumulation in several plant species in vitro. These findings pave the way for a more thorough examination of light as a plant elicitor. The fact that most studies have focused on plant growth and development, including the generation of primary metabolites, highlights the paucity of information about the different factors regulating light elicitation mechanisms. Thus, many studies still lack at depicting the mechanisms of elicitation promoting the production of pharmacologically important secondary metabolites since it may differ depending upon the type of plant species, culture conditions, and light source used.

**Author Contributions:** Conceptualization, S.A.; methodology, M.H., B.A., and S.D.; validation, C.H., B.H.A., and S.A.; formal analysis, S.A.; investigation, M.H., B.A., and S.D.; resources, C.H., B.H.A., and S.A.; data curation, C.H., B.H.A., and S.A.; writing—original draft preparation, M.H., B.A., and S.A.; writing—review and editing, C.H., B.H.A., and S.A.; supervision, C.H., B.H.A., and S.A.; project administration, S.A.; funding acquisition, C.H., B.H.A., and S.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by Cosmetosciences, a global training and research program dedicated to the cosmetic industry. Located in the heart of the Cosmetic Valley, this program led by the University of Orleans is funded by the Region Centre-Val de Loire (VALBIOCOSM and INNOCOSM).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All data are included in the present study.

**Acknowledgments:** B.H.A. and C.H. acknowledge the research fellowship of Le Studium-Institute for Advanced Studies, Loire Valley, Orléans, France. S.D. acknowledges Cosmetosciences and Région Centre Val de Loire for research fellowships. The authors would like to acknowledge networking support by Le Studium COSMENOVIC consortium and CNRS GDR3711 COSM'ACTIFS. The authors gratefully acknowledge the Région Centre Val de Loire for funding the project VALBIOCOSM and INNOCOSM. C.H. and B.H.A. gratefully acknowledge the support of Campus France through the PHC PERIDOT.

**Conflicts of Interest:** The authors declare no conflict of interest.
