Identification of Appropriate Light Intensity and Daytime Temperature for Cucumber (Cucumis sativus L.) Seedlings in a Plant Factory with Artificial Lighting for Use as Grafting Material

Abstract

In this study, an experiment was conducted to suggest optimal daytime temperature and light intensity for cucumber scion and rootstock production in a plant factory with artificial light. Plant growth of cucumber scions and rootstocks at a day/night temperature of 26/18 °C and photosynthetic photon fluxes of 50, 120, 190, 260, 330, and 400 μmol·m−2·s−1 was investigated. Plant growth under daytime temperatures of 25/18, 26/18, 27/18, and 28/18 °C at a photosynthetic photon flux of 260 μmol·m−2·s−1 was investigated. As the photosynthetic photon flux increased, hypocotyl length was shortened in cucumber scions and rootstocks, but Dickson quality index, compactness, and Seedling Health Index were improved. As the daytime temperature increased, the hypocotyl length of cucumber scions increased, but the quality of seedlings decreased. The root growth of scions decreased as the daytime temperature increased. As for the correlation between the major growth indicators, Dickson quality index, compactness, and Seedling Health Index showed a high correlation of more than 0.8 in stem diameter, leaf, and root weight. Therefore, it is judged that it is most efficient to maintain the photosynthetic photon flux at 260 μmol·m−2·s−1 throughout the year and adjust the daytime temperature to 25 to 28 °C according to the season for farms and commercial nurseries that produce cucumber seedlings by installing plant factories with artificial light.