title: The effect of impedance to root growth on plant architecture in wheat.
abstract: OBJECTIVE
  We were interested in the effect of impedance to root growth on root and shoot architecture of wheat. It is known thatRht-1semi-dwarfing alleles decrease the degree of leaf stunting due to root impedance. We compared commercial wheat cultivars containing differentRht-1alleles to determine whether leaf stunting caused by root impedance differed between cultivars. We investigated effects of impedance to root growth on the angular spread of roots.
  
  
  METHODS
  The wheat cultivars Avalon, Robigus and Battalion, carrying semi-dwarfing alleles ofRht-1, and cv. Cadenza, carrying the tall, wild-type allele, were grown under two levels of soil strength in a sand culture system designed to allow the mechanical impedance of the root growth environment to be adjusted independently of water and nutrient availability.
  
  
  RESULTS
  Impeded roots grew more steeply than non-impeded roots: the angular spread of roots decreased from 55° to 43° from the vertical, but the genotypic effects were weak. Root impedance reduced leaf elongation and the number of tillers. Leaf area and total root length provided a common relationship across all genotype x treatment combinations. Leaf stunting in Cadenza was more severe.
  
  
  CONCLUSIONS
  Our data support the hypothesis that the severity of leaf stunting due to root impedance is related to theRhtallele. Impeded roots had a smaller angular spread.
authors.affiliation: Department of Plant Nutrition, College of Resource and Environmental Sciences, China Agricultural University, Beijing, 100193 China ; Rothamsted Research, West Common, Harpenden St Albans, AL5 2JQ UK.
authors.forename: Kemo
authors.initials: K
authors.lastname: Jin
authors.affiliation: Department of Plant Nutrition, College of Resource and Environmental Sciences, China Agricultural University, Beijing, 100193 China.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Shen
authors.affiliation: Rothamsted Research, West Common, Harpenden St Albans, AL5 2JQ UK.
authors.forename: Rhys W
authors.initials: RW
authors.lastname: Ashton
authors.affiliation: Rothamsted Research, West Common, Harpenden St Albans, AL5 2JQ UK.
authors.forename: Rodger P
authors.initials: RP
authors.lastname: White
authors.affiliation: The Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ UK.
authors.forename: Ian C
authors.initials: IC
authors.lastname: Dodd
authors.affiliation: Rothamsted Research, West Common, Harpenden St Albans, AL5 2JQ UK.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Phillips
authors.affiliation: Rothamsted Research, West Common, Harpenden St Albans, AL5 2JQ UK.
authors.forename: Martin A J
authors.initials: MA
authors.lastname: Parry
authors.affiliation: Rothamsted Research, West Common, Harpenden St Albans, AL5 2JQ UK.
authors.forename: William R
authors.initials: WR
authors.lastname: Whalley
keywords: Leaf elongation; Rht alleles; Root growth angle; Root impedance