As a key metabolite with high medical values in industrial hemp, cannabidiol (CBD) has been paid increasing attention. However, how nutrient supply affects the CBD content and yield of hemp remains unclear. Therefore, an aeroponic experiment with nine treatments (A1~A9) was conducted to evaluate the effects of different concentrations of nitrogen (N, at 4.0, 6.0, and 8.0 mmol L⁻¹), phosphorus (P, at 1.0, 1.5, and 2.0 mmol L⁻¹), and potassium (K, at 3.0, 4.0, and 5.0 mmol L⁻¹) on the growth, CBD content, and biomass of hemp. Results showed that at A7 (N8P1K5) (N, P, K: 8, 1, 5 mmol L⁻¹) markedly enhanced the dry weight of shoot and inflorescence with an increment of 208.7% and 435.7% respectively; the equivalent number of total CBD content in inflorescence was increased by 41.8%, and the CBD yield was increased by 7.0 times compared with A3 (N4P2K5). Correlation analysis revealed that N was positively related to the CBD yield, while P or K had a negligible effect on CBD yield. In conclusion, nutrient supply would dramatically influence the growth and CBD yield of hemp. Under the experimental conditions, A7 (N8P1K5) is the most suitable choice to cultivate hemp and achieve a higher CBD yield.

The cellulose synthase gene superfamily is vital for cell wall biogenesis during plant growth, particularly for flax fiber development. This study performed asequencing search of key CESA and CSL genes from several flax stem parts at different fiber development stages by comparing RNA-Seq. Quantitative RT-PCR was used to validate the expression of these genes. This study revealed that CESA4 genes (Lus10008225.g and Lus10008226.g), CESA6 genes (Lus10006161.g and Lus10041063.g), CESA8 genes (Lus10007296.g and Lus10029245.g), CSLD4 gene (Lus10026568.g), CSLE1 (Lus10016625.g) and CSLG genes (Lus10023056.g and Lus10023057.g) were specifically expressed in stem below the snap point where fibers is increased amounts of secondary cell wall deposition. LusCESA4 genes, LusCESA8, genes and LusCSLD4 gene were specifically expressed in fiber development stage during the fast growth period of flax plants. Based on GO and KEGG analyses, it was found that genes involved in pathways of cellulose microfibril organization, galactosyl transferase activity and galactose metabolism were specifically enriched in the stem tissue of the fiber development stage. Other genes involved in cellulose biosynthesis and cell wall development were also analyzed and discussed. The results will provide an important foundation for understanding fiber cell wall biogenesis, particularly the roles of LusCESAs and LusCSLs in the process of fiber development.

Background: The cellulose synthase gene superfamily, including the cellulose synthase (CESA) and cellulose synthase-like (CSL) gene families, is vital for cell wall construction during plant growth, particularly for fiber development of flax, which is an old and important fiber crop. Results: This study performed a sequencing search of key CESA and CSL genes from several flax stem parts at different fiber development stages by comparing RNA-Seq. Quantitative RT-PCR was used to validate the expression of these genes. This study revealed that CESA4 genes (Lus10008225.g and Lus10008226.g), CESA6 genes (Lus10006161.g and Lus10041063.g), CESA8 genes (Lus10007296.g and Lus10029245.g), CSLD4 gene (Lus10026568.g), CSLE1 (Lus10016625.g) and CSLG genes (Lus10023056.g and Lus10023057.g) were specifically expressed in stem tissue below the snap point where fibers is increased amounts of secondary cell wall deposition. LusCESA4 genes, LusCESA8, genes and LusCSLD4 gene were specifically expressed in fiber development stage during the fast growth period of flax plants. Based on GO and KEGG analyses, it was found that genes involved in pathways of cellulose microfibril organization, galactosyl transferase activity and galactose metabolism were specifically enriched in the stem tissue of the fiber development stage. Other genes involved in cellulose biosynthesis were also analyzed and discussed. Conclusion: The results of this study will provide an important foundation for understanding fiber cell wall biogenesis, particularly the roles of LusCESAs and LusCSLs in the process of fiber development.