Root anatomical traits contribute to deeper rooting of maize under compacted field conditions.

Kenneth W Loades,Dorien J Vanhees,Jonathan P Lynch,A Glyn Bengough,Sacha J Mooney,Roland Pieruschka

doi:10.1093/jxb/eraa165

Kenneth W Loades, Dorien J Vanhees + Show 4 more

Open Access

https://doi.org/10.1093/jxb/eraa165

Copy DOI

Abstract

To better understand the role of root anatomy in regulating plant adaptation to soil mechanical impedance, 12 maize lines were evaluated in two soils with and without compaction treatments under field conditions. Penetrometer resistance was 1-2 MPa greater in the surface 30 cm of the compacted plots at a water content of 17-20% (v/v). Root thickening in response to compaction varied among genotypes and was negatively associated with rooting depth at one field site under non-compacted plots. Thickening was not associated with rooting depth on compacted plots. Genotypic variation in root anatomy was related to rooting depth. Deeper-rooting plants were associated with reduced cortical cell file number in combination with greater mid cortical cell area for node 3 roots. For node 4, roots with increased aerenchyma were deeper roots. A greater influence of anatomy on rooting depth was observed for the thinner root classes. We found no evidence that root thickening is related to deeper rooting in compacted soil; however, anatomical traits are important, especially for thinner root classes.

Highlights

Mechanical impedance has important effects on root development and plant growth as it restricts soil exploration and nutrient and water capture (Yamaguchi and Tanaka, 1990; Merotto and Mundstock, 1999; Lipiec and Hatano, 2003; Batey, 2009)
All cell area traits were orthogonally oriented from the cell file number (CF), indicating no correlation between cell area and the number of cell layers.total cortical area (TCA) and root cross-sectional area (RCSA) were correlated to both dimensions and that was due to the fact that traits such as cell file layer versus IN and MID were found on different principal component (PC). cell file layer was not correlated with IN and MID, all these traits were correlated with the cortex, which in turn was related to RCSA
Kirby and Bengough (2002) observed that pea roots, grown in a sandy loam soil, can increase their diameter by 60% when grown at a mechanical impedance of 2 MPa versus 0.7 MPa.When grown in clay loam instead of sandy loam soil, root diameter increased less.Tomato root diameter increased in hard loamy sand more than in hard clay loam, illustrating the importance of soil texture (Tracy et al, 2013).The greater sand fraction and less structured soil, in combination with greater differences in penetrometer resistance between compaction and non-compaction treatment, at the Apache Root Biology Center (ARBC) field site could explain why larger diameters under non-compacted conditions are seen in both nodes versus at the Pennsylvania State University (PSU) field site

Summary

Introduction

Mechanical impedance has important effects on root development and plant growth as it restricts soil exploration and nutrient and water capture (Yamaguchi and Tanaka, 1990; Merotto and Mundstock, 1999; Lipiec and Hatano, 2003; Batey, 2009). Improved understanding of root adaptations to mechanical impedance could contribute to the development of crops with improved exploration of hard soils, commonly encountered in deep soil horizons, with improved water and nutrient acquisition (Lynch and Wojciechowski, 2015). Mechanical impedance >2 MPa reduces root elongation for most plants (Atwell, 1993). Radial thickening is thought to relieve stress from the root tip

Objectives

Methods

Results

Discussion

Conclusion