Relationship Between Tensile Properties And Microscopic Properties Of Herbaceous Plant Roots In Benggang Area

Vegetation restoration is an important method for the management of benggang,the tensile mechanical properties of plant roots are the basis for the study of root-reinforcement,and the tensile properties are related to the microscopic properties of roots.To explore the relationship between root micro-properties and tensile mechanical properties,four herbaceous plants(Cynodon dactylon,Paspalum wettsteinii,Vetiveria zizanioides and Pennisetum sp.),which were planted in benggang area of Changting county,were chosen as study objects.Through the root tensile tests,main chemical composition analysis tests and root microstructure measurement tests,the relationship between root chemical composition,root microstructure and root mechanical properties was obtained.The main conclusions are as follows:(1)Diameter,root length and growth period were important factors affecting the tensile mechanical properties of the four herb roots,but the tensile rate had no significant effect on their tensile properties.There was a power function positive correlation between the maximum root tensile force and diameter,while root tensile strength and diameter showed a negative power function.Under different root length conditions,the maximum root tensile force and tensile strength of the four herbs all showed 30 mm>50 mm>100 mm.When the growth period was 5 months and 9 months,the average root tensile force and tensile strength of four herbs were shown as:9 months>5 months.During the two growth periods,the tensile properties of four herbaceous roots were same,and the order of average tensile force was Pennisetum sp.>Paspalum wettsteinii>Vetiveria zizanioides>Cynodon dactylon,the order of average tensile strength was Pennisetum sp.>Vetiveria zizanioides>Paspalum wettsteinii>Cynodon dactylon.(2)During the same growth period,with the increase of root diameter,root lignin content increased and cellulose content decreased.With the increase of growth period,the hemicellulose and holocellulose content in the four herb roots showed an increasing trend.The average cellulose content in Vetiveria zizanioides decreased,and the other three herbs all increased.The average content of lignin in Cynodon dactylon and Pennisetum sp.decreased,while that of Paspalum wettsteinii and Vetiveria zizanioides increased.In addition to L/C of Vetiveria zizanioides increased,the other hree herbs were basically unchanged.The maximum root tensile force(F)of Cynodon dactylon,Paspalum wettsteinii,Vetiveria zizanioides and Pennisetum sp.was most influenced by lignin content(L),the relationship between them could be expressed as:F=2.73 L-24.21(R2=0.63,P<0.01,n=24).And tensile strength(P)was most influenced by cellulose content(C),the relationship between them could be expressed as:P=2.82 C-60.73(R2=0.43,P<0.01,n=24).(3)The cross-sections of four herb roots at 5 months and 9 months of growth period,from outside to inside were consists of three basic parts of epidermis,cortex and stele,the percentage of cortex area was the largest in 7 microstructures(epidermis,cortex,pericycle,xylem,phloem,pith and stele),followed by the percentage of stele area.The root tensile mechanical properties of four gramineae herbs(Cynodon dactylon,Paspalum wettsteinii,Vetiveria zizanioides and Pennisetum sp.)were mainly affected by the area percentage of epidermis,pericycle and stele,and it was positively related to the percentage of area in pericycle and stele,and negatively correlated with the percentage of epidermis area.The functional relationship between root tensile force(F)and the area percentage of epidermis(Ep),pericycle(Pe)and vascular column(Va)was as follow:F=-2.75 Ep+13.44 Pe+0.46 Va-24.87(R2=0.99,P<0.05,n=24),and the functional relationship between tensile strength(P)and the three was:P--3.36 Ep+16.00 Pe+0.86 Va-25.01(R2=0.99,P<0.05,n=24).