Effect of different light spectra by using coloured plastic films on growth, fresh and dry matter, nutrient solution uptake and secondary metabolites of Perilla frutescens (L.) Britt

• Perilla frutescens with high polyphenol content can be produced in Europe.
• Fresh matter production was not reduced under colored plastic films.
• Under colored plastic film less nutrient solution was taken up.

Effects of two coloured plastic films (‘Half Minus Green 248’ and ‘Pale Lavender 136’)1 with different values of photosynthetically active radiation (‘Half Minus Green 248’: 120 ± 49 μmol m−2 s−1, ‘Pale Lavender 136’: 83 ± 38 μmol m−2 s−1) and light spectra on growth, fresh and dry matter, nutrient solution uptake and secondary metabolites of Perilla frutescens grown in greenhouse were compared to natural light (154 ± 57 μmol m−2 s−1 photosynthetically active radiation). Both films differed in transmission of blue, green and red light, where ‘Pale Lavender 136’ had much lower transmission (62.00% blue, 39.00% green, 71.00% red light) than ‘Half Minus Green 248’ (75.40% blue, 65.25% green, 88.00% red light). ‘Half Minus Green 248’ film had higher red: far-red (660 nm: 730 nm) ratio (0.98) than ‘Pale Lavender 136’ film (0.82), but lower blue: red (400–500 nm: 600–700 nm) ratio (0.83) than ‘Pale Lavender 136’ film (0.92). Fresh matter under the plastic films was not lower than in the control after 3 weeks of cultivation. Compared to control dry matter (15.51%), ‘Pale Lavender 136’ treatment showed no significant difference, while under ‘Half Minus Green 248’ film significantly lower dry matter (13.77%) was recorded. Use of ‘Half Minus Green 248’ film did not have significant influence on nutrient solution uptake, while ‘Pale Lavender 136’ film reduced it by 11.91% comparing to control. Plant height increased significantly by 18.60% under ‘Half Minus Green 248’ film and by 15.61% in ‘Pale Lavender 136’ treatment compared to control which average height was 34 cm. Regarding concentration of secondary metabolites, use of ‘Pale Lavender 136’ film reduced it but not significantly compared to control. Use of ‘Half Minus Green 248’ film resulted in significantly lower concentration of anthocyanins (−81.36%) and polyphenols (−55.74%), as well as in reduced antioxidant activities (−53.63%). The flavonoid concentration did not differ between the treatments. The plant yield and the concentration of secondary metabolites could not be affected positively by the use of these plastic films, but with ‘Pale Lavender 136’ the same yield could be obtained with less nutrient uptake.