Stem Anatomy of Hemp Strains and Physical Properties of Their Extracted Fibers
Camille Pierre Mentors: Prabha Amarasinghe and Aruna Weerasooriya College of Agriculture and Human Sciences and Cooperative Agriculture Research Center
Introduction: Texas recently legalized Hemp (Cannabis sativa). Hemp contains bast and hurd fibers, and they differ in types of cells, chemistry, physical properties, and end-usage1. Retting is a process used to extract fibers, and it can be a chemical or microbial, or enzymatic approach to dissolve specific cells and pectin surrounding the fiber bundles2. The anatomy of the hemp stem is connected to fiber quality and quantity3. This project aims to 1) test anatomical parameters of stems of hemp strains, 2) investigate mechanical properties of fibers, including thermal degradation and shear strength, and 3) determine the best method of retting. The outcomes of this research will contribute to identifying the best fiber strain of hemp for Texas and select the best fiber extraction method. Materials and methods: Strains of hemp (Bialobrzeskie, Portland, and BlueCross) were selected based on some branches and plant heights, and voucher specimens were prepared. Cell distribution of each strain was determined using cross-sections of stems stained with methyl green-Congo red4. Samples were chemically retted with 7% NaOH5. Stems were laid on grasses for dew retting3. Stems were digested with a microbial liquor from rotten vegetables and treated with commercial enzymes for enzymatic retting. Three replicates were used for each treatment. Dry weights of hurd and bast fibers of strains and methods were compared. The fiber strength and tensile stress will be measured using Instron and analyzed with ANOVA on R package6. Results: Bialobrzeskie showed the highest diameter of the cellular layer that formed bast fibers, whereas Portland showed the highest diameter of the lignified hurd fibers. The highest dry weight of bast fibers was recorded for Bialobrzeskie with the enzymatic approach, whereas the highest dry weight of hurd fibers was recorded for Portland digested using enzymes. Chemical retting was the fastest method of extracting fibers for all strains. Results of mechanical strength and heat resistance are still in progress. Conclusions: Both stem cross-sections and dry weights consistently showed that Bialobrzeskie is the best strain for bast fibers, and Portland is best for hurd fibers. Enzymatic retting can be employed if the fiber quantity is the main interest. Future studies include completing physical property testing, using more fiber strains, and identifying microbes in the microbial retting liquor.
References: [1] van den Broeck, H. C., C. Maliepaard, M. J. M. Ebskamp, M. A. J. Toonen, and A. J. Koops. 2008. Differential expression of genes involved in C1 metabolism and lignin biosynthesis in wooden core and bast tissues of fiber hemp (Cannabis sativa L.). Plant Science 174: 205–220. [2] Liu, S., L. Ge, S. Gao, L. Zhuang, Z. Zhu, and H. Wang. 2017. Activated carbon derived from biowaste hemp hurd and retted hemp hurd for CO2 adsorption. Composites Communications 5: 27–30.
6
