ABSTRACT
The 2018 Agricultural Improvement Act removed hemp from Schedule I control, creating a market for hemp products, including cannabidiol-containing products. Due to the market's rapid growth, little is known about the presence and concentration of cannabinoids in commercial products. Herein, 11 cannabinoids were quantified using liquid chromatography with diode-array detection in a non-representative sampling of 147 products labeled as containing hemp or cannabidiol. A subset of 133 products were analyzed for toxic elements using inductively coupled plasma-mass spectrometry. Cannabinoid content ranged from < LOD - 143 mg/serving, with a median of 16.7 mg/serving. Fewer than half of products surveyed contained cannabidiol concentrations within 20 % of their label declarations. The estimated exposure to lead was below the Interim Reference Level of 12.5 µg/day Pb for women of childbearing age, and most products presented concentrations of Δ9-tetrahydrocannabinol below LOQ. These findings emphasize the need for further testing and representative investigation of the cannabidiol marketplace.
ABSTRACT
Polar auxin transport (PAT) is a major determinant of plant morphology and internal anatomy with important roles in vascular patterning, tropic growth responses, apical dominance and phyllotactic arrangement. Woody plants present a highly complex system of vascular development in which isolated bundles of xylem and phloem gradually unite to form concentric rings of conductive tissue. We generated several transgenic lines of hybrid poplar (Populus tremula x alba) with the auxin-responsive DR5 promoter driving GUS expression in order to visualize an auxin response during the establishment of secondary growth. Distinct GUS expression in the cambial zone and developing xylem-side derivatives supports the current view of this tissue as a major stream of basipetal PAT. However, we also found novel sites of GUS expression in the primary xylem parenchyma lining the outer perimeter of the pith. Strands of primary xylem parenchyma depart the stem as a leaf trace, and showed GUS expression as long as the leaves to which they were connected remained attached (i.e., until just prior to leaf abscission). Tissue composed of primary xylem parenchyma strands contained measurable levels of free indole-3-acetic acid (IAA) and showed basipetal transport of radiolabeled auxin ((3)H-IAA) that was both significantly faster than diffusion and highly sensitive to the PAT inhibitor NPA. Radiolabeled auxin was also able to move between the primary xylem parenchyma in the interior of the stem and the basipetal stream in the cambial zone, an exchange that was likely mediated by ray parenchyma cells. Our results suggest that (a) channeling of leaf-derived IAA first delineates isolated strands of pre-procambial tissue but then later shifts to include basipetal transport through the rapidly expanding xylem elements, and (b) the transition from primary to secondary vascular development is gradual, with an auxin response preceding the appearance of a unified and radially-organized vascular cambium.
