Optimizing Growth, Physiology, and Saponin Production in Primula veris L. Through Tailored LED Light Spectra for Energy-Efficient Cultivation

Primula veris L. (cowslip) is a medicinal plant traditionally used for respiratory ailments, with its therapeutic properties attributed to triterpene saponins and phenolic glycosides found in the roots and the aerial parts. The present study aimed to investigate the impact of different LED light spectra (red, blue, red:blue, and white fluorescent as a control) on P. veris’s relative growth rate, physiology, and secondary metabolite production to optimize its cultivation under controlled conditions. The results demonstrate that the light quality significantly influences P. veris’s growth characteristics, physiology, and secondary metabolite production. Red light promoted leaf expansion, while the red:blue LED combination enhanced the root fresh weight and concentration of total chlorophylls and carotenoids in primrose leaves in comparison to the white fluorescent and solitary red light, respectively. Red light significantly increased the accumulation of key secondary metabolites (primeverin, primulaverin, and primulic acids) in roots during the flowering phase compared with the white inflorescent. In addition, the concentration of phenolic compounds was strongly influenced, showing a decrease between the vegetative and the flowering stage of development. Finally, this study highlights the potential of tailored LED lighting to optimize P. veris cultivation, enhancing both biomass and the production of valuable bioactive compounds, taking into account the developmental stage of the plants.