Research and application of LED lighting in the healing stage of grafted vegetable seedlings

A. Koukounaras, F. Bantis, A. Siomos, C. Dangitsis, T. Koufakis, D. Kintzonidis
In Greece, among vegetables, watermelon is exclusively cultivated with the use of grafted plants while high percentages (> 30-50%) of other vegetables (tomato, cucumber, etc.) are also grafted. The production of grafted vegetable seedlings is mainly carried out by modern nurseries and the healing of seedlings is considered as the most critical stage during their production process. Previously, beds inside the greenhouse were used for healing while nowadays they are replaced by chambers with fluorescent (FL) lamps as supplemental light. The aim of the present study was to find the efficacy of LED lamps in the healing chamber as an alternative lighting source for grafted watermelon seedling production. Apart from FL lamps (control treatment with photosynthetic photon flux density (PPFD) of 45 μmol m‑2 s‑1), LEDs employed were 12B (12% blue and 88% red), 12B+FR (12B with 5% supplemental far-red) and AP673L (wide spectra with 12% blue), all providing PPFD of 85 μmol m‑2 s‑1 over plants. The characteristics evaluated were stem length, leaf area, root and shoot weights and their ratio (R/S) as well as leaf colour. According to the results, seedlings treated with 12B and 12B+FR were taller (+11 and +14%, respectively), had larger leaves (+21 and +8%, respectively), greater shoot (+24 and +22%, respectively) and root (+111 and +89%, respectively) biomass, as well as R/S ratio (+65 and +49%, respectively) compared to those treated with FL. On the other hand, seedlings treated with AP673L had higher dry root weight (+46%) and R/S ratio (+32%) compared to those treated with FL. It is concluded that red light supplemented with 12% blue and optionally far-red is ideal for the production of high quality seedlings, while a wide spectrum slightly improved seedling quality.
Koukounaras, A., Bantis, F., Siomos, A., Dangitsis, C., Koufakis, T. and Kintzonidis, D. (2021). Research and application of LED lighting in the healing stage of grafted vegetable seedlings. Acta Hortic. 1302, 79-86
DOI: 10.17660/ActaHortic.2021.1302.11
Citrullus lanatus, nursery, healing chamber, marketable seedlings

Acta Horticulturae