Foliar Symptomology, Nutrient Content, Yield, and Secondary Metabolite Variability of Cannabis Grown Hydroponically with Different Single-Element Nutrient Deficiencies

In controlled environment production systems, Cannabis sativa (hereafter cannabis) is a commodity with high nutrient demands due to prolific growth under optimized environmental conditions. Since nutrient deficiencies can reduce yield and quality, cultivators need tools to rapidly detect and evaluate deficiency symptoms so corrective actions can be taken quickly to minimize losses. We grew cannabis plants in solution culture with different individual nutrient elements withheld from the solutions to identify deficiency symptoms. Control plants received a complete nutrient recipe, whereas the following single elements were withheld from the respective nutrient deficiency treatments: N, P, K, Ca, Mg, S, Fe, and Mn. The nutrient treatments began when the photoperiod was switched to a 12/12 h (light/dark), and plants were grown to commercial maturity. Plants were monitored daily, and the development of visual deficiency symptoms were recorded. Photographs of each plant were taken weekly. Upon the onset of visual deficiency symptoms, both upper- and lower-canopy foliage were analyzed for nutrient element concentrations. At harvest, plants were evaluated for biomass partitioning, and the cannabinoid composition of inflorescence tissues. This manuscript describes the onset and progression of nutrient deficiency symptoms (with pictures), relates symptomology to foliar nutrient analyses, and contextualizes the relationships between nutrient deficiencies and cannabis growth, yield, and quality. Aboveground vegetative fresh weights were reduced by 73% in the -N treatment and 59% in the -P treatment, compared with the control. All deficiency treatments except for -Fe and -Mn had floral yields reduced by between 33% to 72%, compared with the control. Overall, deficiencies of individual nutrients can substantially reduce vegetative growth and inflorescence yield, although only minor effects were observed in secondary metabolite composition. The onset of individual deficiency symptoms did not always correspond with elemental analysis of foliar tissues. Cultivators should take an integrated approach in diagnosing nutrient deficiencies and take timely corrective actions to optimize productivity and minimize losses to yield and quality.

Indoor grown cannabis yield increased proportionally with light intensity, but ultraviolet radiation did not affect yield or cannabinoid content

Cannabis (Cannabis sativa) flourishes under high light intensities (LI); making it an expensive commodity to grow in controlled environments, despite its high market value. It is commonly believed that cannabis secondary metabolite levels may be enhanced both by increasing LI and exposure to ultraviolet radiation (UV). However, the sparse scientific evidence is insufficient to guide cultivators for optimizing their lighting protocols. We explored the effects of LI and UV exposure on yield and secondary metabolite composition of a high Δ⁹-tetrahydrocannabinol (THC) cannabis cultivar 'Meridian'. Plants were grown under short day conditions for 45 days under average canopy photosynthetic photon flux densities (PPFD, 400-700 nm) of 600, 800, and 1,000 μmol m^-2 s^-1, provided by light emitting diodes (LEDs). Plants exposed to UV had PPFD of 600 μmol m^-2 s^-1 plus either (1) UVA; 50 μmol m^-2 s^-1 of UVA (315-400 nm) from 385 nm peak LEDs from 06:30 to 18:30 HR for 45 days or (2) UVA + UVB; a photon flux ratio of ≈1:1 of UVA and UVB (280-315 nm) from a fluorescent source at a photon flux density of 3.0 μmol m^-2 s^-1, provided daily from 13:30 to 18:30 HR during the last 20 days of the trial. All aboveground biomass metrics were 1.3-1.5 times higher in the highest vs. lowest PPFD treatments, except inflorescence dry weight - the most economically relevant parameter - which was 1.6 times higher. Plants in the highest vs. lowest PPFD treatment also allocated relatively more biomass to inflorescence tissues with a 7% higher harvest index. There were no UV treatment effects on aboveground biomass metrics. There were also no intensity or UV treatment effects on inflorescence cannabinoid concentrations. Sugar leaves (i.e., small leaves associated with inflorescences) of plants in the UVA + UVB treatment had ≈30% higher THC concentrations; however, UV did not have any effect on the total THC in thesefoliar tissues. Overall, high PPFD levels can substantially increase cannabis yield, but we found no commercially relevant benefits of adding UV to indoor cannabis production.

Susceptibility and symptom development in Arabidopsis thaliana to Tobacco mosaic virus is influenced by virus cell-to-cell movement

To identify host factors that regulate susceptibility to Tobacco mosaic virus (TMV), 14 Arabidopsis thaliana ecotypes were screened for their ability to support TMV systemic movement. The susceptibility phenotypes observed included one ecotype that permitted rapid TMV movement accompanied by symptoms, nine ecotypes that allowed a slower intermediate rate of systemic movement without symptoms, and four ecotypes that allowed little or no systemic TMV movement. Molecular comparisons between ecotypes representing the rapid (Shahdara), intermediate (Col-1), and slow (Tsu-1) movement phenotypes revealed a positive correlation between the ability of TMV to move cell to cell and its speed of systemic movement. Additionally, protoplasts prepared from all three ecotypes supported similar levels of TMV replication, indicating that viral replication did not account for differences in systemic movement. Furthermore, induction of the pathogenesis-related genes PR-1 and PR-5 occurred only in the highly susceptible ecotype Shahdara, demonstrating that reduced local and systemic movement in Col-1 and Tsu-1 was not due to the activation of known host defense responses. Genetic analysis of F2 progeny derived from crosses made between Shahdara and Tsu-1 or Col-1 and Tsu-1 showed the faster cell-to-cell movement phenotypes of Shahdara and Col-1 segregated as single dominant genes. In addition, the Shahdara symptom phenotype segregated independently as a single recessive gene. Taken together, these findings suggest that, within Arabidopsis ecotypes, at least two genes modulate susceptibility to TMV.