Nutritional value of Asian herbaceous plants under different light conditions suitable for indoor farming

Several Asian herbaceous plants with an importance for the consumption in Europe, were investigated in greenhouse and climate chambers. For further studies were selected Persicaria odorata fam. Polygonaceae and Perilla frutescens var. crispa (Thunb.) H. Deane, fam. Lamiaceae. The aim was to investigate the effect of different light conditions on yield and nutritional value of both species for indoor cultivation. The main light sources were fluorescent light tubes (FT). Daylight integral (DLI), provided by fluorescent tubes, was modified in two groups one chamber 4.68 and another 9.06 mol m^‑2 d^‑1. Whereby the daylight integral was the same by one variant and the respective control but differed between variants, that means values can just be compared between them and not between different variants. The light spectrum was adjusted for cultivation of Persicaria odorata by additional monochromatic LEDs: blue (443 nm) 11 µmol m^‑2 s^‑1, green (515 nm) 7 µmol m^‑2 s^‑1, and red (629 nm) 12 µmol m^‑2 s^‑1. In experiments with Perilla frutescens the control variant (FT) grew with two different light conditions 123.29 or 177.33 µmol m^‑2 s^‑1, by adding of LED with blue (443 nm) and red (629 nm) for the test plants (FT+bLEDs) under 125.62 or (FT+rLEDs) under 197.31 µmol m^‑2 s^‑1, respectively. The increase in light intensity correlated positively with an increase in biomass in both plants (+0.56% +1% increased light intensity for P. odorata, +1.92% for P. frutescens) and resulted in higher flavonoid levels. The levels of polyphenols and anthocyanins (detectable only in P. frutescens) decreased. Modifying the light spectrum by adding LED lighting gave different results: blue LED light increased biomass and decreased polyphenol content in both plants. Red LED light decreased biomass in P. odorata and increased flavonoid content in P. frutescens. Green LED light applied to P. odorata affected polyphenol and flavonoid contents positively (but not significantly). Study proved that Asian herbaceous plants are suitable for indoor farming. By adjusting light conditions (intensity and spectrum), significant increases of yield and nutritional value can be achieved. However, it is to consider the plant species and which of the phytonutrients is of importance, e.g., flavonoids, polyphenols or anthocyanins. Therefore, light conditions should be chosen carefully under consideration of all relevant growth or quality parameters.