A Novel Image-Analysis Technique for Kinematic Study of Growth and Curvature

Abstract

Kinematic analysis has provided important insights into the biology of growth by revealing the distribution of expansion within growing organs. Modern methods of kinematic analysis have made use of new image-tracking algorithms and computer-assisted evaluation, but these methods have yet to be adapted for examination of growth in a variety of plant species or for analysis of graviresponse. Therefore, a new image-analysis program, KineRoot, was developed to study spatio-temporal patterns of growth and curvature of roots. Graphite particles sprinkled on the roots create random patterns that can be followed by image analysis. KineRoot tracks the displacement of patterns created by the graphite particles over space and time using three search algorithms. Following pattern tracking, the edges of the roots are identified automatically by an edge detection algorithm that provides root diameter and root midline. Local growth rate of the root is measured by projecting the tracked points on the midline. From the shape of the root midline, root curvature is calculated. By combining curvature measurement with root diameter, the differential growth ratio between the greater and lesser curvature edges of a bending root is calculated. KineRoot is capable of analyzing a large number of images to generate local root growth and root curvature data over several hours, permitting kinematic analysis of growth and gravitropic responses for a variety of root types.

Developmentally equivalent tissue sampling based on growth kinematic profiling of Arabidopsis inflorescence stems

“…In addition to the 24 plants presented in this study, we have analyzed an additional 51 plants for immunohistochemical and transcriptome analysis (data to be published separately). Manual analysis of an image set for a single plant currently takes c. 2 h, but exciting new advances are being made in the establishment of velocity fields, based upon optical flow (Schmundt et al, 1998;Basu et al, 2007;Nagel et al, 2006). This could potentially facilitate observation of hundreds of plants within a single experiment if such automated feature tracking approaches that rely on natural features of the expanding surface can be adapted to deal with the challenges of imaging primary stems.…”

“…Primarily for this reason, assessment of REGRs from two-dimensional (2D) observation of growing roots (single-point perspective) has largely been conducted on restrictive 2D surfaces such as glass plates (Erickson & Sax, 1956;Basu et al, 2007) or Petri dishes (Hummel et al, 2007;Mullen et al, 1998;Nagel et al, 2006). These data are recognized as being informative despite ongoing * ** r e t f A e r o f e B Fig.…”

“…Measurement of the rates of displacement of carbon particles from the root tip allowed derivation of the relative elemental growth rate (REGR) for points along the root, essentially providing a growth kinematic profile (GKP). More modern approaches have utilized root tip displacement rates, also referred to as the velocity field (Gandar, 1983), as the basis for direct calculation of REGR as a percentage change in length for elements (segments) over time (Schmundt et al, 1998;Basu et al, 2007). REGR data have also been generated indirectly for a number of species (not including Arabidopsis) through a modeling approach that uses a logistic function conditioned by estimated parameters in order to substitute for the missing velocity field data (Morris & Silk, 1992).…”

Root growth ofNicotiana attenuatais decreased immediately after simulated leaf herbivore attack

“…[13][14][15] Clear responses are often seen best in young seedlings as they grow fast and as they can be cultivated in agar-filled, translucent Petri dishes allowing live imaging. Hence, it was the aim of our study to monitor defence reactions in the N. attenuata seedling system while at the same time assessing the dynamics of root growth reaction following such an attack.…”

A high throughput robot system for machine vision based plant phenotype studies

“…In the static setup described in [1], for example, the experiment involved determining the location of the root tip and manually focusing on it so the above assumptions were valid. In [15,23] the authors reduce manual effort by bringing more seedlings within the field of view.…”