The effects of supplementary short-term red leds lighting on nutritional quality of Perilla frutescens L. microgreens

Abstract

The objective of our studies was to evaluate the impact of supplementary short-term red light emitting diodes (LEDs) lighting on the antioxidant properties of Perilla frutescens (L.) microgreens. Perilla frutescens (L.) (var. crispa) Britt., red form, were grown to harvest time (about 20 days) within a greenhouse of Institute of Horticulture, Lithuanian Research Centre of Agricultural and Forestry Science in a peat substrate under daylight (daily average of 20 – 80 µmol m-2s -1) with supplementary lighting provided by high-pressure sodium lamps (HPS) (“Philips”, SON-T Agro). The generated photosynthetic photon flux density (PPFD) of HPS lamps was about 90 μmol m-2s -1. The photoperiod was 18 h, day/night temperature - 22/16°C and relative air humidity - 50-60 %. Three days before harvesting, supplementary lighting from red 638-nm LEDs (PPFD of 210 μmol m-2s -1) was applied with the total PPFD maintained at ~300 μmol m–2 s–1 . To determine effect of short-term red light, reference plants were grown under HPS with PPFD level of ~300 μmol m–2 s–1. Our results revealed that cultivating Perilla frutescens (L.) microgreens, short-term supplemental pre-harvest 638-red lighting can produce higher quality plants due to decreased nitrate content and increased the main antioxidants contents, such as total anthocyanins and ascorbic acid. Such lighting had no effect on DPPH free-radical scavenging activity and flavonols index and resulted in decreased α-tocopherol content. Increased total anthocyanins content also is important for microgreens external quality due to more intensive coloration of red P. frutescens cotyledons.