Hemp (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.

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

Physio-biochemical responses of pistachio varieties including Pistacia vera L. ‘Ghazvini’ (GH), P. vera ‘Ghermez-Pesteh’ (GP) and P. atlantica subsp. mutica (M) were assessed under salt stress to understand the common mechanisms of salt tolerance in two popular Pistacia species. In the experiment, half-sib seedlings of the varieties were subjected to high (100 mM) and severe (200 mM) levels of NaCl-induced salinity for 90 days. Growth, physiological, biochemical and ionic parameters in the roots and shoots of plants were measured in the experiment. Salinity markedly declined plant growth, and increased the number of necrotic leaves (NL) and leaf abscission. In terms of physiological responses, salinity reduced the relative water content (RWC), membrane stability index (MSI) and the concentrations of photosynthetic pigments, but increased carbohydrates and proline content in the leaves. MSI of the leaves was positively correlated with the concentrations of anthocyanins and carotenoids. Salinity increased sodium content in root and shoot tissues of the plants, and decreased potassium concentration and K/Na ratio. Among the rootstocks, GH had better performance on all parameters. Despite the high concentration of Na+ and low K/Na ratio in the shoots, the lowest number of NL was found in GH under both salinity levels. The results indicated that salt tolerance in GH was most likely related to compartmentation of Na+ ions. Finally, accumulation of osmolytes and sodium compartmentation were considered to be the most important mechanisms in the salt tolerance of pistachio rootstocks.

https://www.mdpi.com/2077-0472/11/8/708/pdf

Osmolyte Accumulation and Sodium Compartmentation Has a Key Role in Salinity Tolerance of Pistachios Rootstocks

Previous studies have revealed that some wild wheat accessions respond well to water deficit treatments and have a good potential in terms of photosynthetic parameters, root system architecture, and several physiological properties. However, the biochemical responses and molecular mechanisms of antioxidant-encoding genes remain to be elucidated. Herein, we investigated the most tolerant accessions from A. crassa, Ae. tauschii, and Ae. cylindrica previously identified from a core collection in previous studies, along with a control variety of bread wheat (T. aestivum cv. Sirvan) through measuring the shoot fresh and dry biomasses; the activities of antioxidant enzymes (including ascorbate peroxidase (APX), catalase (CAT), guaiacol peroxidase (GPX), and peroxidase (POD)); and the relative expression of CAT, superoxide dismutase (MnSOD), and GPX and APX genes under control and water deficit conditions. Water deficit stress caused a significant decrease in the shoot biomasses but resulted in an increase in the activity of all antioxidant enzymes and relative expression of antioxidant enzyme-encoding genes. Principal component analysis showed a strong association between the shoot dry biomass and the activity of CAT, POD, and APX, as well as MnSOD gene expression. Thus, these traits can be used as biomarkers to screen the tolerant plant material in the early growth stage. Taken together, our findings exposed the fact that Ae. tauschii and Ae. crassa respond better to water deficit stress than Ae. cylindrica and a control variety. Furthermore, these accessions can be subjected to further molecular investigation.

https://www.mdpi.com/2077-0472/10/9/415/pdf

Wild Relatives of Wheat Respond Well to Water Deficit Stress: A Comparative Study of Antioxidant Enzyme Activities and Their Encoding Gene Expression

The accumulation of anthropogenic heavy metals in soil is a major form of pollution. Such potentially toxic elements are nonbiodegradable and persist for many years as threats to human and environmental health. Traditional forms of remediation are costly and potentially damaging to the land. An alternative strategy is phytoremediation, where plants are used to capture metals from the environment. Industrial hemp (Cannabis sativa) is a promising candidate for phytoremediation. Hemp has deep roots and is tolerant to the accumulation of different metals. In addition, the crop biomass has many potential commercial uses after harvesting is completed. Furthermore, the recent availability of an annotated genome sequence provides a powerful tool for the bioengineering of C. sativa for better phytoremediation.

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Potential of Industrial Hemp for Phytoremediation of Heavy Metals

The production and consumption of nuts are increasing in the world due to strong economic returns and the nutritional value of their products. With the increasing role and importance given to nuts (i.e., walnuts, hazelnut, pistachio, pecan, almond) in a balanced and healthy diet and their benefits to human health, breeding of the nuts species has also been stepped up. Most recent fruit breeding programs have focused on scion genetic improvement. However, the use of locally adapted grafted rootstocks also enhanced the productivity and quality of tree fruit crops. Grafting is an ancient horticultural practice used in nut crops to manipulate scion phenotype and productivity and overcome biotic and abiotic stresses. There are complex rootstock breeding objectives and physiological and molecular aspects of rootstock-scion interactions in nut crops. In this review, we provide an overview of these, considering the mechanisms involved in nutrient and water uptake, regulation of phytohormones, and rootstock influences on the scion molecular processes, including long-distance gene silencing and trans-grafting. Understanding the mechanisms resulting from rootstock × scion × environmental interactions will contribute to developing new rootstocks with resilience in the face of climate change, but also of the multitude of diseases and pests.

Advances in Rootstock Breeding of Nut Trees: Objectives and Strategies.

Industrial activities have a detrimental impact on the environment and health when high concentrations of pollutants are released. Phytoremediation is a natural method of utilizing plants to remove contaminants from the soil. The goal of this study was to investigate the ability of Cannabis sativa L. to sustainably grow and remediate abandoned coal mine land soils in Pennsylvania. In this study, six different varieties of industrial hemp (Fedora 17, Felina 32, Ferimon, Futura 75, Santhica 27, and USO 31) were grown on two different contaminated soil types and two commercial soils (Miracle-Gro Potting Mix and PRO-MIX HP Mycorrhizae High Porosity Grower Mix). Plants growing in all soil types were exposed to two environmental conditions (outside and in the greenhouse). Seed germination response and plant height indicated no significant differences among all hemp varieties grown in different soils, however on an average, the height of the plants grown in the greenhouse exceeded that of the plants grown outdoors. In addition, heavy metal analysis of Arsenic, Lead, Nickel, Mercury, and Cadmium was performed. The concentration of Nickel was 2.54 times greater in the leaves of hemp grown in mine land soil outdoors when compared to greenhouse conditions. No differences were found between expression of heavy metal transporter genes. Secondary metabolite analysis of floral buds from hemp grown in mine land soil displayed a significant increase in the total Cannabidiol content (2.16%, 2.58%) when compared to Miracle-Gro control soil (1.08%, 1.6%) for outdoors and in the greenhouse, respectively. Molecular analysis using qRT-PCR indicated an 18-fold increase in the expression of the cannabidiolic acid synthase gene in plants grown on mine land soil. The data indicates a high tolerance to heavy metals as indicated from the physiological and metabolites analysis.

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Enhanced tolerance of industrial hemp (Cannabis sativa L.) plants on abandoned mine land soil leads to overexpression of cannabinoids

Salinity substantially affects plant growth and crop productivity worldwide. Plants adopt several biochemical mechanisms including regulation of antioxidant biosynthesis to protect themselves against the toxic effects induced by the stress. One-year-old pistachio rootstock exhibiting different degrees of salinity tolerance were subjected to sodium chloride induced stress to identify genetic diversity among cultivated pistachio rootstock for their antioxidant responses, and to determine the correlation of these enzymes to salinity stress. Leaves and roots were harvested following NaCl-induced stress. The results showed that a higher concentration of NaCl treatment induced oxidative stress in the leaf tissue and to a lesser extent in the roots. Both tissues showed an increase in ascorbate peroxidase, superoxide dismutase, catalase, glutathione reductase, peroxidase, and malondialdehyde. Responses of antioxidant enzymes were cultivar dependent, as well as temporal and dependent on the salinity level. Linear and quadratic regression model analysis revealed significant correlation of enzyme activities to salinity treatment in both tissues. The variation in salinity tolerance reflected their capabilities in orchestrating antioxidant enzymes at the roots and harmonized across the cell membranes of the leaves. This study provides a better understanding of root and leaf coordination in regulating the antioxidant enzymes to NaCl induced oxidative stress.

https://www.mdpi.com/2218-273X/10/2/189/pdf

Sodium Chloride Induced Stress Responses of Antioxidative Activities in Leaves and Roots of Pistachio Rootstock.

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Rabab Husain

Papers

Enhanced tolerance of industrial hemp (Cannabis sativa L.) plants on abandoned mine land soil leads to overexpression of cannabinoids

Sodium Chloride Induced Stress Responses of Antioxidative Activities in Leaves and Roots of Pistachio Rootstock.

Sodium Chloride-Induced Salt Stress Responses of Antioxidative Activities in Leaves and Roots of Pistachio Rootstock