Study of different LED light impacts on growth mechanisms and secondary metabolites production in cell cultures of Matricaria chamomilla L. through analysis of H2O2 level, antioxidative responses, and cell ultrastructure

Light plays a crucial role in plant growth, development, and the biosynthesis of secondary metabolites. Due to their cost-effectiveness and spectral specificity, light-emitting diodes (LEDs) are widely used in controlled agricultural systems, including greenhouses, in vitro culture, and plant tissue and cell culture systems. In the present study, the effects of different LED light spectra on the physiological and biochemical responses of Matricaria chamomilla L. cell cultures were investigated, with particular emphasis on biomass accumulation and secondary metabolite production. Calli derived from chamomile hypocotyl explants were transferred to Murashige and Skoog (MS) liquid medium, and the resulting cell cultures were subsequently cultured on MS solid medium. After one week of culture, the cells were exposed to different LED light treatments (white, blue, red, red-blue) and darkness as the control. Samples were collected after one, two, and three weeks of exposure. The results showed that red-blue light promoted the highest biomass accumulation, followed by blue light, compared to other light treatments. The greatest activities of peroxidase (POX) and superoxide dismutase (SOD) were observed under blue light after three weeks of treatment, and the highest activity of catalase (CAT) was observed under red, white, and blue lights, respectively. Interestingly, the lowest and highest hydrogen peroxide (H 2 O 2 ) and malondialdehyde (MDA) contents across the various growth stages were measured under red-blue light and blue light, respectively. Enhanced oxidative stress under blue light was further confirmed by microscopic observations. All light treatments induced the biosynthesis of phenolic and flavonoid metabolites as well as phenylalanine ammonia lyase (PAL) activity during the three-week culture period, with the highest levels under blue light. Overall, these findings indicate that blue light has greater potential for enhancing the production of bioactive secondary metabolites, whereas red-blue light is more favorable for biomass accumulation in chamomile cell cultures.