title: Root cortical aerenchyma inhibits radial nutrient transport in maize (Zea mays).
abstract: OBJECTIVE
  Formation of root cortical aerenchyma (RCA) can be induced by nutrient deficiency. In species adapted to aerobic soil conditions, this response is adaptive by reducing root maintenance requirements, thereby permitting greater soil exploration. One trade-off of RCA formation may be reduced radial transport of nutrients due to reduction in living cortical tissue. To test this hypothesis, radial nutrient transport in intact roots of maize (Zea mays) was investigated in two radiolabelling experiments employing genotypes with contrasting RCA.
  
  
  METHODS
  In the first experiment, time-course dynamics of phosphate loading into the xylem were measured from excised nodal roots that varied in RCA formation. In the second experiment, uptake of phosphate, calcium and sulphate was measured in seminal roots of intact young plants in which variation in RCA was induced by treatments altering ethylene action or genetic differences.
  
  
  RESULTS
  In each of three paired genotype comparisons, the rate of phosphate exudation of high-RCA genotypes was significantly less than that of low-RCA genotypes. In the second experiment, radial nutrient transport of phosphate and calcium was negatively correlated with the extent of RCA for some genotypes.
  
  
  CONCLUSIONS
  The results support the hypothesis that RCA can reduce radial transport of some nutrients in some genotypes, which could be an important trade-off of this trait.
authors.affiliation: Department of Plant Science, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Hu
authors.forename: Amelia
authors.initials: A
authors.lastname: Henry
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Brown
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Lynch
mesh_terms: D001692:Biological Transport; D002118:Calcium / Q000493:pharmacokinetics; D010710:Phosphates / Q000493:pharmacokinetics; D010761:Phosphorus Radioisotopes / Q000493:pharmacokinetics; D018517:Plant Roots / Q000033:anatomy & histology* / Q000378:metabolism* / Q000502:physiology; D013431:Sulfates / Q000493:pharmacokinetics; D052584:Xylem; D003313:Zea mays / Q000033:anatomy & histology* / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: D010710:Phosphates; D010761:Phosphorus Radioisotopes; D013431:Sulfates; D002118:Calcium
keywords: Aerenchyma; Zea mays; calcium; maize; nutrient uptake; phosphorus; radial transport; root; sulfur