Relationship between root tensile mechanical properties and main chemical components of five herbaceous species

To explore the effect of root chemical components on the mechanical properties of five common herbaceous species in Central China, root tensile tests were conducted on their roots. The tested roots were divided into four groups with diameters ranging from 0 to 1.5 mm, and then their root chemical components such as cellulose, lignin, and hemicellulose content were measured. In addition, the holocellulose and ratio of lignin to cellulose contents were calculated. The results showed that the root tensile force and strength of the five species were in the following descending order: Vetiveria zizanioides＞Paspalum natatu＞Cynodon dactylon＞Zoysia matrella＞Setaria viridis in each diameter class. A comparison of the different species in each group revealed that the tensile properties of V. zizanioides and P. natatu were significantly higher than those of the other three species were (P0.05). Furthermore, the different diameter classes of the five species showed a significantly increased tensile force while the tensile strength decreased significantly with increasing root diameter. Both the tensile force and strength were shown to be power functions (P0.05). The analysis of the root chemical components showed that the values were in the range of 21.90%~34.57%, 12.85%~19.42%, 14.31%~19.34%, 38.52%~51.83%, and 0.37~0.83 for the cellulose, lignin, hemicellulose, holocellulose, and ratio of lignin to cellulose content, respectively. Interestingly, the root diameter of the five species was negatively correlated with the cellulose and holocellulose contents but positively correlated with the lignin and the ratio of lignin to cellulose contents. However, no significant correlation was found between the hemicellulose content and root diameter. The root tensile force was negatively correlated with the cellulose and holocellulose content, and positively correlated with the ratio of the lignin to cellulose content while the root tensile strength was positively correlated with the cellulose and holocellulose content, and negatively correlated with the lignin and the ratio of lignin to cellulose content. All the correlations were statistically significant, and the above the results indicate that cellulose, holocellulose, lignin, and the ratio of lignin to cellulose contents exhibited a good correlation with the mechanical properties of the herbaceous species roots. Therefore, this study provided useful information on the relationship between the mechanical properties, chemical components, and diameter of these plant roots.