Introduction: Hemp (Cannabis sativa L.) is one of the most important non-wood fiber crops. In addition to its medicinal applications, it has attracted considerable attention in the textile, papermaking, bio-based composite, and other industries because of its high-quality bast fibers. Hemp is commonly classified based on cannabinoid composition, particularly the content and ratio of tetrahydrocannabinol (THC) and cannabidiol (CBD), and genetic and molecular approaches have been widely used to distinguish drug and fiber chemotypes. However, the role of anatomical and fiber biometric characteristics in differentiating these types has received far less attention. Because fiber biometric traits directly influence fiber quality and performance in various end products, understanding potential differences between drug and fiber types is important for evaluating their industrial value. Therefore, this study aimed to investigate and compare the biometric characteristics of bast and xylem fibers in type I and type III hemps and to identify the traits contributing to their differentiation.
Method: Ten C. sativa genotypes, including five Type I and five type III genotypes, were examined. Type I genotypes were THC-dominant and are generally associated with medicinal and psychoactive uses, whereas Type III genotypes were CBD-dominant and more closely resemble industrial fiber hemp in terms of cannabinoid composition. Three stems were sampled from each type. After separating the bark from the woody core, the samples were macerated using Franklin’s method. Fiber biometric traits of bast and xylem fibers, including fiber length, fiber width, lumen width, and cell wall thickness, were measured. Stem height and bark thickness were also recorded. Data were analyzed using a linear mixed-effects model (LMM), independent t-tests, and Mann–Whitney tests. Principal component analysis (PCA) was used to investigate overall patterns of trait variation, linear discriminant analysis (LDA) was employed to assess the discriminatory power of the measured traits, and Pearson correlation analysis was conducted to evaluate relationships among variables. Comparisons between bast and xylem fibers were performed using paired t-tests.
Results: Among the ten examined traits, only bast fiber width and bast fiber wall thickness differed significantly between drug and fiber hemp types. In both cases, drug types exhibited higher values than fiber types. In contrast, no significant differences were observed in bast or xylem fiber length, xylem fiber width, lumen width, xylem fiber wall thickness, stem height, or bark thickness. Principal component analysis showed that the first two principal components explained more than 52% of the total variance, and the relative separation between the two groups was primarily associated with transverse fiber characteristics. Linear discriminant analysis further revealed that cell wall thickness, fiber width, and lumen width, particularly in xylem fibers, were the most important traits contributing to the differentiation of drug and fiber hemp types. Correlation analysis indicated that bast fiber traits and xylem fiber traits were more strongly correlated within their respective tissue systems than between them. Comparisons between bast and xylem fibers showed that bast fibers were significantly longer and had thicker cell walls in both groups, whereas xylem fibers, particularly in fiber hemp types, had larger lumens.
Conclusion: The results showed that although drug-type and fiber-type hemp can be distinguished based on certain anatomical characteristics, substantial overlap exists between them, and only a limited number of fiber biometric traits differ significantly. The most important finding of this study is that transverse fiber characteristics, particularly fiber width and cell wall thickness, play a greater role in differentiating drug and fiber hemp types than fiber length, which showed no significant difference between the two groups. Furthermore, the observed differences between bast and xylem fibers reflect their distinct functional roles within the hemp stem. These findings may contribute to breeding programs, the selection of suitable genotypes for industrial applications, and a better understanding of the relationship between fiber structure and performance in hemp.