title: Growth rate distribution in the forming lateral root of arabidopsis.
abstract: OBJECTIVE
  Microscopic observations of lateral roots (LRs) in Arabidopsis thaliana reveal that the cross-sectional shape of the organ changes from its basal to its apical region. The founder cells for LRs are elongated along the parent root axis, and thus from the site of initiation the base of LRs resemble an ellipse. The circumference of the apical part of LRs is usually a circle. The objective of this study was to analyse the characteristics of changes in the growth ﬁeld of LRs possessing various shapes in their basal regions.
  
  
  METHODS
  The LRs of the wild type (Col-0) and two transgenic arabidopsis lines were analysed. On the basis of measurements of the long and short diameters (DL and DS, respectively) of the ellipse-like ﬁgure representing the bases of particular LRs, their asymmetry ratios (DL/DS) were determined. Possible differences between accessions were analysed by applying statistical methods.
  
  
  RESULTS
  No significant differences between accessions were detected. Comparisons were therefore made of the maximal, minimal and mean value of the ratio of all the LRs analysed. Taking into consideration the lack of circular symmetry of the basal part, rates of growth were determined at selected points on the surface of LRs by the application of the growth tensor method, a mathematical tool previously applied only to describe organs with rotational symmetry. Maps showing the distribution of growth rates were developed for surfaces of LRs of various asymmetry ratios.
  
  
  CONCLUSIONS
  The maps of growth rates on the surfaces of LRs having various shapes of the basal part show differences in both the geometry and the manner of growth, thus indicating that the manner of growth of the LR primordium is correlated to its shape. This is the ﬁrst report of a description of growth of an asymmetric plant organ using the growth tensor method. The mathematical modelling adopted in the study provides new insights into plant organ formation and shape.
authors.affiliation: Department of Biophysics and Plant Morphogenesis, University of Silesia, Katowice, Poland jsp@us.edu.pl.
authors.forename: Joanna
authors.initials: J
authors.lastname: Szymanowska-Pułka
authors.affiliation: Department of Biophysics and Plant Morphogenesis, University of Silesia, Katowice, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Lipowczan
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000254:growth & development*; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D008962:Models, Theoretical; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000254:growth & development*; D030821:Plants, Genetically Modified
keywords: Arabidopsis thaliana; lateral root formation; plant organ morphology; rate of growth
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