title: Relationships between root diameter, root length and root branching along lateral roots in adult, field-grown maize.
abstract: OBJECTIVE
  Root diameter, especially apical diameter, plays an important role in root development and function. The variation in diameter between roots, and along roots, affects root structure and thus the root system's overall foraging performance. However, the effect of diameter variation on root elongation, branching and topological connections has not been examined systematically in a population of high-order roots, nor along the roots, especially for mature plants grown in the field.
  
  
  METHODS
  A method combining both excavation and analysis was applied to extract and quantify root architectural traits of adult, field-grown maize plants. The relationships between root diameter and other root architectural characteristics are analysed for two maize cultivars.
  
  
  RESULTS
  The basal diameter of the lateral roots (orders 1-3) was highly variable. Basal diameter was partly determined by the diameter of the bearing segment. Basal diameter defined a potential root length, but the lengths of most roots fell far short of this. This was explained partly by differences in the pattern of diameter change along roots. Diameter tended to decrease along most roots, with the steepness of the gradient of decrease depending on basal diameter. The longest roots were those that maintained (or sometimes increased) their diameters during elongation. The branching density (cm(-1)) of laterals was also determined by the diameter of the bearing segment. However, the location of this bearing segment along the mother root was also involved - intermediate positions were associated with higher densities of laterals.
  
  
  CONCLUSIONS
  The method used here allows us to obtain very detailed records of the geometry and topology of a complex root system. Basal diameter and the pattern of diameter change along a root were associated with its final length. These relationships are especially useful in simulations of root elongation and branching in source-sink models.
authors.affiliation: Key Laboratory of Arable Land Conservation (North China), Ministry of Agriculture, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wu
authors.affiliation: INRA, UR 1115 PSH, Site Agroparc, 84914 Avignon cedex 9, France and.
authors.forename: Loïc
authors.initials: L
authors.lastname: Pagès
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, Key Laboratory of Crop Cultivation and Farming System, Center of Crop Chemical Control, College of Agriculture and Biotechnology, China Agricultural University, Beijing 100193, China wujie.cau@gmail.com.
authors.forename: Jie
authors.initials: J
authors.lastname: Wu
mesh_terms: D018517:Plant Roots / Q000033:anatomy & histology* / Q000254:growth & development*; D019655:Quantitative Trait, Heritable; D003313:Zea mays / Q000033:anatomy & histology* / Q000254:growth & development*
keywords: Lateral roots; branching density; branching order; growth potential; maize.; root diameter; root length; root system architecture