Tensile properties of seminal and nodal roots and their relationship with the root diameter and planting density of maize (Zea mays)

Abstract

The tensile property of roots is an important factor for anchorage and for resistance to root lodging. In this study, a root tensile test was applied to maize (Zea mays L.) grown in the field at three planting densities, 4.5 × 104, 6.75 × 104 and 9.0 × 104 plants ha–1, to quantify the maximum tensile force (Fmax) and tensile strength (Ts) of roots at the V10 stage (tenth leaf visible) and grain-filling stage. In addition, relationships among tensile properties, diameter and turgid weight : dry weight (TW : DW) ratio of roots were investigated. The results showed that the Fmax of primary and seminal adventitious roots was lower than of nodal roots. Among nodal roots, the Fmax of roots on upper nodes was higher. Planting density significantly affected the tensile force of nodal roots of the sixth to eighth tiers; their Fmax decreased with increasing planting density. A positive linear correlation between Fmax and root diameter and a power function between Ts and root diameter was observed. In addition, there was a positive linear correlation between the TW/DW ratio and root diameter and a negative exponential correlation between Ts and TW : DW ratio. Therefore, nodal roots with a lower TW : DW ratio could have a larger Ts, because their cells are smaller and cell walls are thicker. This result suggests that nodal roots with small and thick cells benefit the tensile properties of maize.