Supplemental light with different blue and red ratios in the physiology, yield and quality of Impatiens

• LED 83R:17B increased the cuttings number per Impatiens plant in winter by 35.4%. • Anthocyanin content in Impatiens leaves did not increase with the use of LED. • Impatiens mother plants did not show oxidative stress with LED use and keep quality. • The 83R:17B LED reduced plugs height Impatiens White by 21.3%, even after light off. • The 67R:33B and 83R:17B LEDs, increased average 41.0% trichomes number on leaves. The yield of many ornamental plant species decreases sharply in the fall and winter seasons due to the decrease in solar radiation and temperature. The aim of this study was to verify the response of two Impatiens hybrid hort cultivars Sunpatiens Compact Royal Magenta and Sunpatiens Compact White to LED supplemental light with different ratios of red and blue: 83% red (640-660 nm): 17% blue (460-470 nm), 75% red (640-660 nm): 25% blue (460-470 nm), 67% red (640-660 nm): 33% blue (460-470 nm), and 50% red (640-660 nm): 25% red (620-630 nm): 25% blue (460-470 nm); and control (only natural light). Plants were grown in a nursery greenhouse at Atibaia, SP, Brazil, with day and night air temperature of 28°C and 21°C, respectively. Mother plants were grown with a spacing of 12 cm x 14 cm in plastic boxes (36 cm width x 56 cm length x 14 cm height) with 50% vermiculite and 50% perlite. Lights were placed at 1 m distance from the plants base, emitting a PPFD of 150 µmol m −2 s −1 . The daily supplemental light for 12 hours (6 am to 6 pm) began after mother plants transplant and was maintained for seven months until the end of the experiment. The yield and quality of both mother plants and cuttings collected from them, as well as of the plugs developed after three weeks were evaluated regarding to biometric characteristics, pigments, antioxidant enzymes, stress indicators, photosynthetic activity and trichomes counting. Impatiens response varied according to the growing season. In the winter season, at 202 DAT, the 83R:17B LED light increased in 35.4% the number of cuttings produced per plant compared to the control. The light supplementation with different spectral proportions did not cause oxidative stress of the Impatiens mother plants, maintaining its quality. The performance of Royal Magenta cv. differed from the White cv. regarding to the use of artificial lighting, mainly due to the higher concentration of anthocyanin in leaves of the Royal Magenta cv. The supplemental light effect during the cuttings production of the White cv. continued until the final phase of the plugs production, due to more compact cuttings produced in the 83R:17B LED light treatment.