Effect of root age on the biomechanics of seminal and nodal roots of barley (Hordeum vulgare L.) in contrasting soil environments

The biomechanics of root systems influence plant lodging resistance and soil structural stabilisation. Tissue age has the potential to influence root biomechanical properties through changes in cell wall chemistry, root anatomy and morphology. Within a root system the internal structures of roots are known to vary markedly within different root types. Nodal, seminal and lateral roots of Barley (Hordeum vulgare) have differing biomechanical behaviour in tension. This study examines the effects of root age on biomechanical properties of barley root types (Hordeum vulgare) under abiotic stress. Root age was determined as a function of the distance from root tip with abiotic stresses consisting of waterlogging and restriction to root elongation rate through increased soil bulk density. Linear regression analyses were performed on log-transformed tensile strength and Young's modulus data with best fits determined for single and multiple parameter models to root morphological properties. Regression co-efficients and Akaike values showed that distance from root tip (taken as a proxy of root age) was the best single variable for prediction of both root tensile strength and Young's modulus. Incorporation of both distance from root tip and root diameter and root type increased the reliability of predictions for root biomechanical properties from 47 to 57 % for tensile strength and 35 to 62 % for Young's modulus. The age effect may partly explain some scatter in both Young's modulus and tensile strength to diameter relationship, commonly cited in the literature.