S25 - Session O4 - Impact of increasing light intensity on plant growth, floral yield and secondary metabolites of medicinal Cannabis

Authors: Wannida Sae-Tang *, Kjell Sneeuw , Mexx Holweg, Céline C.S. Nicole, Sabrina Carvalho, Iris F. Kappers , Ep Heuvelink, Leo F.M. Marcelis

Medicinal cannabis ( Cannabis sativa L.) contains various secondary metabolites in flowers such as cannabinoids and terpenes. Cultivation in indoor farms using artificial light allows a precise control of the quality and quantity of production. A high light intensity may increase production and biosynthesis of secondary metabolites, but it comes at the expense of use energy. The aim of this study is to examine the effects of light intensity on photosynthesis, growth, floral yield and secondary metabolites of medicinal cannabis. Three different light intensities were applied during the short day phase (a 12-h photoperiod) in a cannabis cultivar with high CBD content. Light intensity was 600, 800 and 1000 µmol m -2 s -1 as provided by broad band white LED lamps with a dominant red composition. The maximum photosynthetic rate and light compensation point determined from the light response curve were higher in plants grown under high light intensity. Increasing the light intensity increased stem diameter while plant height was not different from plants grown under lower light intensities. Neither time to first visible flower buds nor flowering were influenced by light intensity. The total plant dry mass and the fraction of dry matter partitioned to the flowers increased with increasing light intensity. Both these factors made floral yield to increase with increasing light intensity. Furthermore, an allometric relationship was observed between the increase in floral yield and stem diameter. For the abundance of some cannabinoids, they increased when grown at higher light intensities.