Light intensity can be used to modify the growth and morphological characteristics of cannabis during the vegetative stage of indoor production

• Published in: Industrial crops and products Vol. 183; p. 114909
• Main Authors: Moher, Melissa, Llewellyn, David, Jones, Max, Zheng, Youbin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2022
• Subjects: Daily light integral; Growth; Light-emitting diodes; Morphology; Photosynthetic photon flux density; DLI; PAR; ST; GI; IL; Growth; APPFD; Photosynthetic photon flux density; WC; Light-emitting diodes; ΔH; Daily light integral; Morphology; FWHM; ΔNN; PPFD; LI; SLW
• ISSN: 0926-6690; 1872-633X
• DOI: 10.1016/j.indcrop.2022.114909

Although the vegetative stage of indoor cannabis (Cannabis sativa) production can be relatively short in duration, there is a high energy demand due to higher light intensities (LI) than the clonal propagation stage and longer photoperiods than the flowering stage (i.e., ≥ 16 vs. 12 h). While electric lighting is a major component of both energy consumption and overall production costs, there is a lack of scientific information to guide cultivators in selecting a LI that corresponds to their vegetative stage production strategies. To determine the vegetative plant responses to LI, clonal plants of ‘Gelato’ (indica-dominant hybrid genotype) were grown for 21 days with canopy-level photosynthetic photon flux densities (PPFD) ranging between 135 and 1430 µmol·m−2·s−1 with a 16-h photoperiod (i.e., daily light integrals of 7.8–82.4 mol·m−2·d−1). Plant height and growth index (i.e., a canopy volume metric) responded quadratically; the number of nodes, stem thickness, and aboveground dry weight increased asymptotically; and internode length and water content of aboveground tissues decreased linearly with increasing LI. Foliar attributes had varying responses to LI. Chlorophyll content index (i.e., SPAD value) increased asymptotically, leaf size decreased linearly and specific leaf weight increased linearly with increasing LI. Generally, PPFD levels of ≈ 900 µmol·m−2·s−1 produced compact, robust plants while PPFD levels of ≈ 600 µmol·m−2·s−1 promoted more open plant architecture (i.e., taller plants with longer internodes), which can increase intra-canopy airflow and may reduce development of potential foliar pests in compact (e.g., indica-dominant) genotypes. •Cannabis sativa ‘Gelato’ plants were grown under different light intensities using 16-h photoperiod per day.•Plant height and growth index responded quadratically to increasing light intensity.•Asymptotic responses for nodes, stem thickness, chlorophyll content, and aboveground dry weight as light intensity increased.•The leaf size, internode length, and water content of aboveground tissues decreased linearly with increasing light intensity.•Light intensity can be used to modify plant’s architecture during the vegetative stage.