Design Modulated Light on Physiological and Molecular Processes in Phenolic Compounds Production of Ocimum basilicum L.

Microgreens (young, edible plantlets) are a remarkable opportunity for both consumers, to benefit from health promoting compounds and for applied research, as such organisms have a very high plasticity related to environmental cues, allowing biotechnology development with low costs. Ocimum basilicum species naturally synthesize valuable, phenolic compounds, among which rosmarinic acid is most prominent. Basil plantlets were grown for 10 days under either full spectrum light (white light) or modulated blue:red:far-red:UV spectrum with an additional factorization, by applying fertilisation. Biomass accumulation reached up to 0.8 g/20 plantlets, while chlorophyll fluorescence was in the 0.75 – 0.78 range and remained uniform across treatments, indicating that no significant stress was exerted under modified light treatment. However, total phenolic contents and, in particular, rosmarinic acid contents were markedly enhanced (up to 7.5 mg/g in the red cultivar) under modulated light treatment and fertilization, compared to full spectrum light. Moreover, gene expression was enhanced, 1.3-6.3 fold for genes coding for enzymes involved in phenylpropanoid synthesis patwhays, such as phenylalanine ammonia lyase (PAL), Catechol-O-methyltransferase (COMT) and renin-angiotensin system (RAS). Overall, light modulation coupled with fertilization led to the production of basil microgreens with up to 10% more total phenolics and up to 25% more rosmarinic acid.