Quantifying root deformation caused by soil radial pressure: A case study with vetiver grass (Vetiveria zizanioides)

Abstract

Roots in compacted soil experience both axial resistance and radial pressure. Axial resistance at root apex and radial pressure perpendicularly at root surface cause root deformation i.e., change in root shape. Although the effects of axial resistance are well described in literature, there is a lack of quantitative approach to examine the radial impact. In addition to morphological observation in root cross sections, this study quantified the radial impact of compacted soil on root surface and vascular cylinder by measuring root roundness (R) and flattening (F) of vetiver (Vetiveria zizanioides L.) seedlings. The plants grown in high bulk density soil (1.58 g cm-3) exhibited uneven root surface with invaginations, reduced R and increased F in root hair zone, compared with plants in low bulk density soil (1.20 g cm-3). However, soil compaction had little effect on vascular cylinder in terms of microscopic observation, the R and F values. It is concluded that the measurements of root roundness (R) and flattening (F) are consistent with microscopic observations and can be used to quantify root deformation under soil compaction.