EZ-Rhizo software: the gateway to root architecture analysis

Abstract

Plants are sessile organisms that have to cope with the available nutritional resources and environmental constraints in the place where they germinate. To fully exploit their nearby resources, they have evolved a highly plastic and responsive root system. Adaptations to limited nutrients include a wide range of specific root responses, e.g., the emergence of new root types, root branching or specific growth of lateral roots. These root system architecture (RSA) features are of utmost importance when investigating the underlying mechanisms by forward, reverse or quantitative genetic approaches. The EZ-Rhizo software was developed to facilitate such root measurements in a fast, simple and accurate way. The performances of EZ-Rhizo in providing about 20 primary and derived RSA parameters were illustrated by looking at natural variability across 23 Arabidopsis accessions. The different RSA profiles obtained from plants grown in favorable condition illustrated the wide reservoir of natural genetic resources underlying specific features of root growth. This diversity was used here to correlate the RSA genetic variability with growth, development and environmental properties of accession origins.

Keywords: Arabidopsis thaliana; image analysis; natural variation; root architecture; software.

Figure 1

Schematic representation of RSA parameters measured by EZ-Rhizo. Main root (MR) primary features: path length (dashed line), vector length (grey arrow), vector angle (α), number of lateral root (LR, black dots). MR derived features: straightness (path:vector lengths), MR root depth (d), basal zone (path length between the root collar and the position of the first LR, white box on the left side), branched zone (path length between the first and the last LR position, grey box on the left side) and apical zone (path length from the position of the last LR to the root tip, black box on the left side), LR density over the MR, LR density over the branched zone. Lateral root (1^st or n order) primary features: position on the MR (or on the LRn-1), path length, vector length, vector angle, number of LRn+1 (open dots). Derived LR features: straightness (path:vector lengths). Overall root feature: total root size (sum of all root path length). LR (or LRn) are numbered according to their position on the MR (or LRn-1). LR parameters are illustrated here only for LR1.