Impacts of Commercial and Custom Substrates on Rooting and Morphology of Cannabis sativa 'Suver Haze' Stem

초록

. Commercial Cannabis sativa propagation is based primarily on asexually propagated stem cuttings to maintain consistent cannabinoid, terpene, and flower yields. Selection of appropriate substrates is critical for successful root and shoot growth during propagation. The present study investigated the effects of three commercial substrates and a custom mix on rooting and growth characteristics of C. sativa L. 'Suver Haze' stem cuttings and characterized the physical and chemical properties of the growth media. Fifty-cell plug trays (74 cm3/cell) were filled with one of four substrates: rockwool (RW), 100% coir (CO), 100% peatmoss (PM), or a custom mix of 50% peatmoss + 50% perlite (PM + PL). The experiments were performed under controlled conditions in a growth chamber. Uniform stem cuttings (apical shoot cuttings with two nodes) were rooted at 24 +/- 1 degrees C air temperature and 65 +/- 5% relative humidity, with an 18-h photoperiod and a photosynthetic photon flux density of 120 +/- 10 mmol & centerdot;m-2 & centerdot;s-1. Substrate moisture was restored to water container capacity with water [pH 7.2; electrical conductivity (EC), 0.20 dS & centerdot;m-1]. After 9 days, cuttings in the PM + PL and CO substrates exhibited higher rooting efficiency (percentage of cuttings rooted) compared with those in RW and PM substrates (41.3% and 29.3% vs. 0% and 16%, respectively). In the PM + PL substrate, root length and fresh and dry mass of cuttings showed significantly higher values (13.0 cm, 495.6 mg, and 21.1 mg, respectively) than those of the other substrates. Moreover, compared with the substrate that exhibited the lowest value for each parameter, plants rooted in PM + PL showed 20% greater stem diameter, 48% more axillary buds, and 104% higher photosynthetic rate. PM + PL presented optimal pH compared with PM (5.50 vs. 4.77) and better EC and air space compared with those in RW and CO (0.42 vs. 0.05 and 0.11 dS & centerdot;m-1, and 7.0% vs. 1.9% and 3.4%, respectively). In conclusion, substrates with physical and chemical characteristics similar to PM + PL could be more suitable for rooting cannabis crops because they are correlated with enhanced rooting efficiency, gas exchange, substrate water retention, and surface area for root development.

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