Hemp Growth Research Articles

Yield potential and factor influencing yield gap in industrial hemp cultivation under nemoral climate conditions

Hemp (Cannabis sativa L.) is a productive multi-purpose crop that can be cultivated in different climatic conditions including northern latitudes. However, no comprehensive study on the hemp yield potential has been conducted, particularly in high latitude regions. This study investigates hemp development and the suitability of the AgroC model to simulate hemp growth in cool climate. Field experiments were conducted at the Lithuanian Research Centre for Agriculture and Forestry on Endogleyic Endostagnic Endocalcaric Luvisol. The AgroC model was calibrated using data sets from 2019, whereby validation was performed with 2020−2021 data sets. The model provided adequate results when simulating hemp and its individual parts biomass, leaf area index, soil water content, and development stages. The validated model was further used to provide hemp yields and water as well as temperature limited yield gaps for the historical 1990−2021 period. Simulated average hemp biomass potential reached up to 20.1 t ha−1. Average biomass yield losses due to water stress are 8.7 t ha−1 (gap 43.3 %), while reduction due to low temperatures may reach 6.4 %, but mean reduction was only 0.4 t ha−1 (gap 2.0 %). Simulated results showed water stress as the main factor defining hemp yield losses, while low temperatures are of secondary importance.

Effects of Light Spectra on Morphology, Gaseous Exchange, and Antioxidant Capacity of Industrial Hemp.

One of the most important growth factors in cannabis cultivation is light which plays a big role in its successful growth. However, understanding that how light controls the industrial hemp growth and development is poor and needs advanced research. Therefore, a pot study was conducted to investigate the effects of different colors of light, that is, white light (WL), blue light (BL), red light (RL), and 50% red with 50% blue mix light (RBL) on morphology, gaseous exchange and antioxidant capacity of industrial hemp. Compared with WL, BL significantly increase hemp growth in terms of shoot fresh biomass (15.1%), shoot dry biomass (27.0%), number of leaves per plant (13.7%), stem diameter (10.2%), root length (6.8%) and chlorophyll content (7.4%). In addition, BL promoted net photosynthesis, stomatal conductance, and transpiration, while reduces the lipid peroxidation and superoxide dismutase and peroxidase activities. However, RL and RBL significantly reduced the plant biomass, gas exchange parameters with enhanced antioxidant enzymes activities. Thus, blue light is useful for large-scale sustainable production of industrial hemp.

Phytoremediation of a pyrene-contaminated soil by Cannabis sativa L. at different initial pyrene concentrations

This study proposes the phytoremediation of a pyrene (PYR)-contaminated soil by Cannabis sativa L. The experimental campaign was conducted along a 60 days period using three different initial PYR concentrations (i.e., 50, 100 and 150 mg kg TS−1 of soil) in 300 mL volume pots under greenhouse conditions (18–25 °C and 45–55% humidity). After 60 days of hemp growth and flourishing, the highest PYR removal reached approximately 95% in planted soil, 35% higher than in the unplanted control. PYR accumulation was observed in both roots and aerial parts of the plant, with a higher PYR uptake at increasing initial PYR concentrations in soil. The initial PYR concentration affected the growth and, thus, the phytoremediation potential of C. sativa L., which was the result of different removal mechanisms. Overall, the lowest initial PYR concentration was the one that resulted in the highest PYR removal. The interaction between the plant roots and microorganisms in rhizosphere was likely associated with PYR removal in this study. The highest DHO activity of 66.26 μg INTF g−1 TS−1 was observed in the soil spiked with 50 mg PYR·kg TS−1.

The cannabinoid profile and growth of hemp (Cannabis sativa L.) is influenced by tropical daylengths and temperatures, genotype and nitrogen nutrition

Hemp (Cannabis sativa L.) has regained worldwide interest as a crop across temperate and subtropical regions. However, there is a paucity of information about the responses of hemp to environmental conditions and interactions between genotype and environment. This study compared the growth responses of a temperate hemp variety (Morphet Late) and three tropical/subtropical varieties (ECO-GH15, ECO-MC16 and ECO-YP16) to tropical daylengths (11.5 h and 12.5 h), temperatures and varying nitrogen (0, 50, 100, 150 kg ha-1 of N) rates. Three experiments under controlled environmental conditions were conducted to test the growth, and cannabinoid production responses to N. Analysis of phenological data revealed significantly different responses between varieties in terms of days to emergence, time to flowering, growth patterns and final biomass showing predominant responses to daylength or temperature depending on the variety. Two tropical/subtropical varieties (ECO-GH15, ECO-MC16) responded similarly under all conditions; the other (ECO-YP16) showed a marked response to temperature rather than daylength, although all varieties had a strong biomass response to N increase. For all varieties, except the temperate variety, the concentration of Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), and some minor cannabinoids were significantly increased by a one-hour daylength increase. This study highlights the importance of temperature, daylength, and nitrogen for growth, time to flowering, and cannabinoid concentrations of different hemp varieties grown under tropical conditions and shows the importance of selecting low THC varieties for production in tropical/subtropical environments.

Effect of zeolite and cow manure application on soil nitrogen content in ramie (Boehmeria nivea) plant growth

Ramie productivity can achieve optimum through improving soil fertility and adding cow manure and zeolite to the soil. The research was conducted in 2018 at Karangploso Research Station-ISFRI. The research design used was a completely randomized design with two factors of manure and zeolite, three replications. Cow manure treatments consisted of no cow manure (P0), 2 tons cow manure (P1), 4 tons cow manure (P2), 6 tons cow manure (P3), while zeolite treatments consisted of no zeolite (Z0) and 4 tons zeolite/ha (Z1). The results showed that the application of zeolite and cow manure affected soil properties and the growth of ramie. The combination treatment of fertilizer and zeolite gave various values of pH, N, C-organic, plant height, and the number of leaves, although there was no interaction. The best results were found in treating 6 tons/ha of cow manure and 4 tons/ha of zeolite with pH values: 6.37 and 6.26; N-Total 0.14% and 0.15%; C-Organic: 1.14% and 1.13%, respectively. Treatments of 6 tons cow manure and 4 tons zeolite gave the best hemp growth, namely plant height at 84 (Days After Planting), DAP 123.23 cm and 98.5 cm, and the number of leaves 104 80.

Hemp Pest Spectrum and Potential Relationship between Helicoverpa zea Infestation and Hemp Production in the United States in the Face of Climate Change.

Simple SummaryCultivation of industrial hemp Cannabis sativa in the United States is now being expanded due to the recent legalization of the crop. Multiple insect pests attack the crop. One of the common pests is the corn earworm Helicoverpa zea that causes extensive damage to the marketable parts of hemp. Changing global climate may lead to expansion of the geographic range of insect pests. Thus, growers of this crop in the United States have to face new and intense pest problems now and in the years to come. Here, we assess the potential relationship between corn earworm infestation and hemp production in the US in the face of climate change. We also provide an update on the arthropods associated with hemp cultivation across the US. Climate change can affect aspects of interactions between hemp and corn earworm. Temperature and photoperiod affect the development and diapause process in H. zea. Drought leads to a reduction in hemp growth. Overall, our assessment suggests the selection of varieties resistant to stresses from climate and insects. Host plant diversity may prevent populations of corn earworm from reaching outbreak levels. Ongoing research on effective management of H. zea on hemp is critical.There has been a resurgence in the cultivation of industrial hemp, Cannabis sativa L., in the United States since its recent legalization. This may facilitate increased populations of arthropods associated with the plant. Hemp pests target highly marketable parts of the plant, such as flowers, stalks, and leaves, which ultimately results in a decline in the quality. Industrial hemp can be used for several purposes including production of fiber, grain, and cannabidiol. Thus, proper management of pests is essential to achieve a substantial yield of hemp in the face of climate change. In this review, we provide updates on various arthropods associated with industrial hemp in the United States and examine the potential impact of climate change on corn earworm (CEW) Helicoverpa zea Boddie, a major hemp pest. For example, temperature and photoperiod affect the development and diapause process in CEW. Additionally, drought can lead to a reduction in hemp growth. Host plant diversity of CEW may prevent populations of the pest from reaching outbreak levels. It is suggested that hemp varieties resistant to drought, high soil salinity, cold, heat, humidity, and common pests and diseases should be selected. Ongoing research on effective management of CEW in hemp is critical.

Hemp Growth Factors and Extraction Methods Effect on Antimicrobial Activity of Hemp Seed Oil: A Systematic Review

The bioactive Hemp Seed Oil (HSO) is becoming very popular in the medical and research fields due to its antimicrobial properties against several diseases caused by bacteria and fungi. However, the effect of hemp-growing factors and extraction methods on the bioactivity of HSO does not receive adequate research attention. Therefore, this review aims to investigate the effect of growth factors and extraction methods on the antimicrobial activity of HSO. Articles were retrieved from Google Scholar and the Scopus database and screened against inclusion and exclusion criteria. The study revealed that HSO prefers warm climates and favorable humidity ranging from 20 to 39 °C and 79–100% per year, respectively, and rainfall of 324 mm daily. The multivariate linear regression shown excellent prediction (R2 = 0.94) with climates upon Zone of Growth Inhibition (ZGI) of Gram-positive bacteria. Temperature is the strongest predictor (p < 0.01) followed by humidity and rainfall (p < 0.05). Furthermore, well-drained loam soil rich in organic matter seems to stimulate the antimicrobial activity of HSO. The major constituents that influence HSO’s antimicrobial ability to Staphylococcus aureus were cannabidiol (CBD), β-caryophyllene, and limonene. The extraction methods showed less influence on the HSO bioactivity. HSO did not show significant antioxidant activity, but Hemp Seed Hull (HSH), Hemp Seed Flour (HSF), and Hydrolyzed Hemp Seed Protein (HPH), expressed promising DPPH scavenging ability.

EFFECT OF VERMICOMPOST DOSES ON CANABIS SATIVA PHOTOSYNTHESIS-RELATED PARAMETERS, GROWTH AND YIELD

Hemp, Cannabis sativa is certainly a mul­tifunctional as well as a niche crop, due to great po­ten­tial for innovative use of its different products. Aspects of hemp mineral nutrition are very important in the cultivation of these plants, in particular to make cul­ti­vation environmentally friendly by replacing synthetic fertilizers with organic ones. Among organic fertilizers, vermicompost has gained particular attention within the last decades. Explaining the role of vermicompost, this study evaluated the effects of different doses of this fer­ti­lizer on hemps in two separate field studies. In a small-scale field experiment, the effect of two doses of ver­micompost and adequate concentrations of mineral elements fertilizers the growth, physiological condition, as well as yield of hemp was compared. The effect of increasing doses of vermicompost on the physiological condition and yield of hemp was analysed in a broader field experiment. The experiments were performed at the Viļāni Scientific Centre of the Agricultural Resour­ces and Economics, in 2017 and 2018, using the Latvian hemp cultivar ‘Pūriņi’. For the experiments, certified vermicompost produced by ‘Eko Zeme’ (Latvia) was used, which was produced from composted cow manure by adding grass biomass. In field experiment, the posi­tive effect of vermicompost on hemp growth was greater than the effect of equivalent mineral fertilizer con­centra­tions. When using vermicompost in increasing doses, better hemp growth (40–60 %) was observed at 5 and 10 t ha-1, stem yield increased on average by 40 % due vermicompost, seed yield ranging from 1.00 t ha-1 in control plants, to 1.56 t ha-1 in 20 t ha-1 in plants treated with 20 t ha–1 vermicompost plants. The weight of 1000 seeds per plant in all variants (from 13.54 to 13.85 g) was relatively close to the indicated maximum level (14.59 g). A statistically significant increase in chlo­ro­phyll concentration in plant leaves was observed under the influence of vermicompost. The increase in the Per­for­mance Index of the chlorophyll a fluorescence measu­rement was only for plants in individual experimental variants; regardless of how significant the increase in stem and seed yield was due to the respective doses of vermicompost. In general, the results characterize the growth of hemp in local agroclimatic conditions and allow to expect a stable increase in yield under the in­fluence of vermicompost.

Properties of Frost-Retted Hemp Fibers for the Reinforcement of Composites

ABSTRACT Frost-retted hemp fibers were investigated to assess their suitability for composite applications. Chemical analysis of frost-retted hemp fibers highlighted a high amount of solubles (pectins) at the fibers surface and a low lignin content in the fibers that was attributed to an unfavorable synthesis of lignin in the cell wall due to the particularly cold temperature during hemp growth in the Nordic countries. The fibers tensile properties were considered at two different scales and the performances of hemp/PLA composites were assessed. Recommendations were provided for the use of frost-retted hemp fibers in the reinforcement of thermoplastic composites.

Wavelengths of LED light affect the growth and cannabidiol content in Cannabis sativa L

Given the special pharmacological value of cannabidiol (CBD), industrial hemp (hemp) has become a real “hot” crop. Though indoor farming of hemp has been widely used, the effects of red and blue light-emitting diode (LED) acting as supplementary light on the CBD synthesis in hemp remains unclear. Herein, a pot experiment with six treatments [CK, high-pressure sodium as light source, (R:B (ratio of red light to blue light) 9.30:1, PPFD (photosynthetic photon flux density) 191); LED1 (R:B 9.20:1; PPFD 129); LED2 (R:B 1.61:1; PPFD 540); LED3 (R:B 6.47:1; PPFD 28.2); LED4 (R:B 7.15:1; PPFD 41.7); LED5 (R:B 16.8:1; PPFD 252)] was carried out to study the effects of LED light quality on the growth and cannabinoid synthesis of hemp. Results showed that LED2 and LED5 could well maintain hemp growth compared with CK in terms of plant height, stem diameter, and leaf numbers. Compared with CK, the treatment of LED1, LED4, and LED3 significantly decreased the aboveground biomass, while LED2 and LED5 notably improved the aboveground biomass with an increment of 15.2 % and 55.1 %; the biomass of hemp flowers for LED2 and LED5 was markedly increased compared with that for CK with increments of 238 % and 61.5 %, respectively, but the other LED light treatments significantly reduced the flowers yield; LED2 could significantly increase the CBD content of both leaves (1.81 %) and flowers (5.83 %) compared to CK (leaves 1.38 %, flowers 4.27 %) while LED5 only notably increased the CBD content of leaves; among the LED treatments, the theoretic CBD yield for a per plant of LED2 and LED5 was 26.8 % and 9.0 % higher than that of CK. In conclusion, different red and blue LED light intensity ratios would dramatically influence the growth and cannabinoid synthesis of hemp, LED2 and LED5 can be good choices for indoor farming of hemp targeted for higher CBD yield.

Sunn hemp (Crotalaria juncea) weed suppression and allelopathy at different timings

ABSTRACT The utilisation of plant allelopathy is an important tool in a diversified weed management strategy. Allelochemicals are released by some plants, such as sunn hemp (Crotalaria juncea L.), to inhibit the growth of neighbouring plants. This species was tested for use as an allelopathic plant for weed control in cropping systems. The allelopathic properties of sunn hemp were tested under field conditions at different timings of 4, 8, 12 and 16 weeks after planting (WAP). The results showed that sunn hemp at 8, 12 and 16 WAP significantly decreased the total number of weeds compared with the control weedy check. The similar trend of decreasing weed number was observed in grass and broadleaf weeds, as well as sedge. The allelopathic activity of sunn hemp was further investigated in the soil planted with sunn hemp and water extracts on tested plants. Phytotoxicity of the soil, planted with sunn hemp at different timings, did not significantly decrease germination, shoot length, root length and dry weight of tested plants. However, the water extracts caused significantly decreased germination and plant growth, especially the shoot extracts exhibited the inhibitory effects more than the root extracts. Interestingly, the extracts from sunn hemp at 4 WAP had higher inhibitory effects than the extracts from other stages. These results suggest that sunn hemp growth stage is an important consideration for maximising biological weed control in cropping systems.

Potential of hemp (Cannabis sativa L.) for paired phytoremediation and bioenergy production

AbstractHemp (Cannabis sativa L.) is a multi‐use crop that has been investigated for its potential use in phytoremediation of heavy metals, radionuclides, and organic contaminants, and as a feedstock for bioenergy production. A review of research literature indicates that hemp is a suitable crop for phytoremediation, and a competitive option for bioenergy. Coupling phytoremediation and bioenergy production from a single hemp crop is a potential solution to overcoming the economic constraints of phytoremediation projects. The current challenge is ensuring that the extracted contaminants are not introduced into the consumer marketplace. After several decades of limited research on hemp in the United States, the purpose of this review is to identify the knowledge available for hemp applications in phytoremediation or in production of bioenergy, and if and how those two purposes have been combined. The literature shows that hemp growth has been demonstrated successfully at the field scale for phytoremediation and in several bioenergy conversion technologies. Little is known about the fate of contaminants during hemp growth or during post‐harvest processing, especially the relationships between hemp genetics, metabolomics, and contaminant partitioning. Complicating the understanding is the expectation that contaminant fate will be dependent on the contaminant type, the concentration in the material, and the processing methods. Before hemp from phytoremediation applications can be used for bioenergy, the fractionation of heavy metals, radionuclides, and/or organic compounds during transesterification, anaerobic digestion, fermentation, and/or combustion of hemp must be evaluated.

Effect of Fertilization and Weed Management on Weed Flora of Hemp Crop

Hemp is known to have a competitive advantage over weeds. Despite its suppressive ability, weed infestation remains an important issue during the early growth of the crop. The aim of this study was to determine the effect of fertilization and weed management on weed flora and hemp growth parameters during initial growth in the 2019 season. The experiment was laid out in a split-split plot design with three replicates: three hemp cultivars as main plots, three fertilization treatments as sub-plots and two sub-sub-plots (weedy, weed free). For the computation of height and biomass weight, 10 plants were randomly selected in each plot. Weed species were collected by quadrate and density and biomass weight were determined. ANOVA revealed that all factors and their interactions significantly affected plant traits. Hemp cultivars showed different competitive ability. ‘Futura 17’ reduced weed measurement traits better than ‘Uso 31’. Density and biomass of nitrophilous weeds increased with the higher N dose compared to control (up to 56% and 79% respectively), therefore negatively affecting the growth of the hemp plants. Further research is needed in order to identify useful information on interactions between weeds and hemp crop to address potential yield losses under different weed management systems.

Comparative evaluation of antioxidant activity of Cannabis sativa L. using FRAP and CUPRAP assays

Cannabis is one of the oldest plants on earth, which is known and used for medical purposes. There are many articles on hempseed oil research in the scientific databases, while the antioxidant activity of Cannabis sativa L. herb extracts has not been extensively studied yet, to our knowledge. In the present study, antioxidant properties of different Cannabis sativa L. varieties from different regions of Lithuania were examined. Spectrophotometric FRAP (ferric reducing antioxidant power) and CUPRAC (cupric reducing antioxidant capacity) methods were used for determination. It was found that Cannabis sativa L. herb extracts possess antioxidant activity. The strongest antioxidant activity was evaluated in the Futura variety and the lowest in Manoica. The obtained results showed that a statistically significant (p ˂ 0.05) higher reductive power was determined by analysing the raw material by the spectrophotometric FRAP method. According to the hemp growth location in Lithuania, the highest TEAC values were estimated in the samples from the North region.

Energy and carbon footprint assessment of production of hemp hurds for application in buildings

Construction is considered as one of the most relevant sectors in terms of environmental impacts, due to the significant use of raw materials, fossil energy consumption and the consequent Greenhouse Gases emissions. The use of unconventional and environmentally-friendly materials and technologies is worldwide recognised as a key factor to enable the decrease of material and energy consumption in buildings. Between natural/sustainable materials, those using hemp products and by-products (fibres and hurds) have rapidly widened their field of application in the building industry, mainly because of their good hygrothermal and acoustic insulation properties. Moreover, the usage of these materials allows high carbon storage due to the CO2 sequestration during the agricultural phase.This study represents an energy and environmental assessment of hemp crop cultivation in France, carried out through a Life Cycle Assessment approach, showing positive and negative contribution related to the different life cycle phases. The total CF evaluated through the IPCC, 2013 GWP 100 method (IPCC, 2013) is equal to 0.975 kgCO2eq, in view of a CO2 uptake of −1.29 kgCO2eq. So, it is understood that the total CF results therefore lower than the CO2 uptake due to the biogenic carbon captured and stored during hemp growth. The total Energy Footprint, instead, was calculated in 17.945 MJ. The Upstream phase came out as the main contributor to the impacts. A sensitivity analysis was performed to explore changes in results related to main inputs assumptions and, in particular, the environmental benefits associated with the replacement of conventional fertilisers (ammonium sulphate) with organic matter were highlighted.

The Effects of Inoculation with Three Glomus Species on Growth and Pb Uptake by Hemp (Cannabis Sativa) in a Pb-Contaminated Soil

Increasing levels of hazardous heavy metals, which enter soil and water ecosystems have had a detrimental effect on global living organisms and needs special attention. The effect of inoculation with three Glomus mycorrhizal fungi (G. mosseae, G. etunicatum and G. constrictum) on hemp growth and some biological properties was evaluated in a soil contaminated with different levels of lead (0, 600, 1200 and 1800mg·kg-1 Pb soil) in the form of Pb(NO3)2. The results show that shoot and root dry weights decreased with increasing Pb levels in soil. But Pb concentration in roots and shoots of hemp increased significantly with increasing Pb levels in soil. However the growth of mycorrhizal inoculated hemps was significantly higher than that of non-inoculated hemp. Mycorrhizal inoculation increased the concentration of Pb in the shoot and root of hemp. In this study, both translocation factor (TF) and enrichment factor (EF) were < 1 and decreased with increasing Pb concentration in soil. The TF was higher in non-inoculated hemp than inoculated hemps. It shows the inhibition effect of mycorrhiza in translocation of Pb from root to shoot. The EF of all inoculated hemps (0.18) was significantly greater than non-inoculated hemp (0.17), showing increased uptake of Pb due to inoculation with mycorrhiza. Simple linear regressions show that the diethylenetriaminepentaacetic acid (DTPA) extractable Pb is more suitable index for evaluating the toxicity effect of soil Pb than the total Pb content.

Comprehensive evaluation of sewage sludge and sewage sludge char soil amendment impact on the industrial hemp growth performance and heavy metal accumulation

Industrial hemp (Cannabis sativa L.) has emerged as a potential multipiurpose crop: fibre crop, energy crop, and phytoextractor of pollutants from the soil. However, the multipurpise grwoth of hemp was restricted as its cultivation in EU was legalized only in the past two decades. Most scientific researches of sewage sludge (SS) describe it at relatively low application levels for cultivation of different crops. Such lack of information requires a wide range of practices for fertilizing hemp with high level of sewage sludge or sewage sludge char (SSCh) doses. At this moment there are no guidelines for sewage sludge char fertilization of energetic plants, depending on soil type. The aim of the study was to analyze and compare SS and SSCh soil application effect on industrial hemp (Cannabis sativa L.) growth performance, and heavy metals accumulation to determine optimum SS or SSCh application rates for the growth of hemp. The experimental design consisted of four treatments: 1–25; 2–50; 3–100; 4–200 of sewage sludge and sewage sludge char Mg ha−1, and control soil (clay loam). It was determined that hemp ability to accumulate heavy metals depending on fertilisation intensity of sewage sludge and sewage sludge char decreased in all parts. Heavy metal distribution of hemp was selective; therefore their contents were decreasing in the following order: roots > stems > leaves. The study has confirmed the nutritional value of SS and SSCh. The potential of using the sewage sludge and its char as a source of organic matter for improvement of clay loam soil and a reasonable production of bioenergy crop like hemp without the use of inorganic fertilizers was shown.

Distribution of cell-wall polysaccharides and proteins during growth of the hemp hypocotyl.

The immuno-ultrastructural investigation localized cell-wall polysaccharides of bast fibers during hemp hypocotyl growth. Moreover, for the first time, the localization of a peroxidase and laccase is provided in textile hemp. In the hypocotyl of textile hemp, elongation and girth increase are separated in time. This organ is therefore ideal for time-course analyses. Here, we follow the ultrastructural rearrangement of cell-wall components during the development of the hemp hypocotyl. An expression analysis of genes involved in the biosynthesis of cellulose, the chief polysaccharide of bast fiber cell walls and xylan, the main hemicellulose of secondary cell walls, is also provided. The analysis shows a higher expression of cellulose and xylan-related genes at 15 and 20days after sowing, as compared to 9days. In the young hypocotyl, the cell walls of bast fibers show cellulose microfibrils that are not yet compacted to form a mature G-layer. Crystalline cellulose is detected abundantly in the S1-layer, together with unsubstituted/low-substituted xylan and, to a lesser extent, in the G-layer. The LM5 galactan epitope is confined to the walls of parenchymatic cells. LM6-specific arabinans are detected at the interface between the cytoplasm and the gelatinous cell wall of bast fibers. The class III peroxidase antibody shows localization in the G-layer only at older developmental stages. The laccase antibody shows a distinctive labelling of the G-layer region closest to the S1-layer; the signal becomes more homogeneous as the hypocotyl matures. The data provide important insights on the cell wall distribution of polysaccharide and protein components in bast fibers during the hypocotyl growth of textile hemp.

Seed germination of hemp (Cannabis sativa L.) cultivars responds differently to the stress of salt type and concentration

Industrial hemp is worldwide, but the effects of salt stress on hemp growth remain unknown, especially the tolerance of different varietal to salt stress during germination. Two important hemp cultivars in China, Yunma 5 (YM5, fiber hemp) and Bamahuoma (BM, seed hemp), were germinated under the conditions with four kinds of salts (NaCl, Na2SO4, Na2CO3, NaHCO3) at 0–300 mM for seven days to test the seed germination responses to salt stress. The germination indexes decreased with the increase of salt concentration for each salt, especially in 300 mM Na2CO3, showing the most toxic effect on germination. However, a low concentration (50 mM) of neutral salt stimulated seed germination, showing a higher germination rate and longer radicles and hypocotyls than the control. The growth of radical and hypocotyl was more salt-sensitive than seed germination. Upon transfer to distilled water, the non-germinated seeds restored germination ability and the recovery percentage increased with the increase of salt concentration. YM5 showed stronger salt tolerance than BM, with higher threshold salinity of 150 mM NaCl and Na2SO4 (100 mM NaCl and 50 mM Na2SO4 for BM), and higher critical salinity of 150 mM Na2CO3 and 250 mM NaHCO3 (100 mM Na2CO3 and 200 mM NaHCO3 for BM) for germination rate. In conclusion, the inhibition of salt stress to hemp seed germination varied with the salt type, salt concentration, and tested cultivars, and both hemp cultivars were more sensitive to alkaline salt stress.

Comparative life cycle assessment of magnesium binders as an alternative for hemp concrete

To counter the negative environmental impact, particularly greenhouse gas emission generated by the construction industry, many low-impact materials are being produced and researched having neutral CO2 emissions and low thermal conductivity. One of these materials is lime-hemp concrete, a self-bearing bio-based insulation material with low thermal conductivity and good CO2 uptake but with weak mechanical properties. In this study alternative magnesium binders are proposed to substitute the traditionally used lime binder in hemp concrete, comparing the environmental impact of these binder composites. To make the comparison, experimental mixtures with both traditionally used and alternative binder composites were produced and their mechanical and thermal properties tested. The magnesium binders showed promising results as these composites were approximately two times stronger, having similar density and thermal conductivity. Afterwards the Life Cycle Assessment (LCA) was carried out to evaluate and compare the environmental impact of all tested composites. Lime based binder composites achieved negative CO2 emissions, varying from −46.5 to −68.6 kg CO2/m3. Alternative binder, magnesium phosphate cement, demonstrated significantly greater environmental impact than all other binders due to its hardener, potassium phosphate, which is highly energy and resource intensive. Magnesium oxychloride cement showed promising results with bio-based filler, as their combined environmental impact was lower in most categories compared to lime-hemp concrete, and negative CO2 emissions of −37.38 kg CO2/m3 were achieved. These negative CO2 emissions were achieved with biogenic CO2 uptake from hemp growth and low binder content, thus achieving low thermal conductivity of 0.062 W/m2*K at 214 kg/m3 density.