title: Variation for N Uptake System in Maize: Genotypic Response to N Supply.
abstract: An understanding of the adaptations made by plants in their nitrogen (N) uptake systems in response to reduced N supply is important to the development of cereals with enhanced N uptake efficiency (NUpE). Twenty seven diverse genotypes of maize (Zea mays, L.) were grown in hydroponics for 3 weeks with limiting or adequate N supply. Genotypic response to N was assessed on the basis of biomass characteristics and the activities of the nitrate ([Formula: see text]) and ammonium ([Formula: see text]) high-affinity transport systems. Genotypes differed greatly for the ability to maintain biomass with reduced N. Although, the N response in underlying biomass and N transport related characteristics was less than that for biomass, there were clear relationships, most importantly, lines that maintained biomass at reduced N maintained net N uptake with no change in size of the root relative to the shoot. The root uptake capacity for both [Formula: see text] and [Formula: see text] increased with reduced N. Transcript levels of putative [Formula: see text] and [Formula: see text] transporter genes in the root tissue of a subset of the genotypes revealed that predominately ZmNRT2 transcript levels responded to N treatments. The correlation between the ratio of transcripts of ZmNRT2.2 between the two N levels and a genotype's ability to maintain biomass with reduced N suggests a role for these transporters in enhancing NUpE. The observed variation in the ability to capture N at low N provides scope for both improving NUpE in maize and also to better understand the N uptake system in cereals.
authors.affiliation: Australian Centre for Plant Functional Genomics, School of Agriculture Food and Wine, University of Adelaide Adelaide, SA, Australia ; School of Agriculture, Food and Wine, University of Adelaide Adelaide, SA, Australia.
authors.forename: Trevor
authors.initials: T
authors.lastname: Garnett
authors.affiliation: Australian Centre for Plant Functional Genomics, School of Agriculture Food and Wine, University of Adelaide Adelaide, SA, Australia ; School of Agriculture, Food and Wine, University of Adelaide Adelaide, SA, Australia.
authors.forename: Darren
authors.initials: D
authors.lastname: Plett
authors.affiliation: Australian Centre for Plant Functional Genomics, School of Agriculture Food and Wine, University of Adelaide Adelaide, SA, Australia ; School of Agriculture, Food and Wine, University of Adelaide Adelaide, SA, Australia.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Conn
authors.affiliation: Australian Centre for Plant Functional Genomics, School of Agriculture Food and Wine, University of Adelaide Adelaide, SA, Australia ; School of Agriculture, Food and Wine, University of Adelaide Adelaide, SA, Australia.
authors.forename: Simon
authors.initials: S
authors.lastname: Conn
authors.affiliation: Mathematics Department, Bethlehem University Bethlehem, Palestine.
authors.forename: Huwaida
authors.initials: H
authors.lastname: Rabie
authors.affiliation: DuPont Crop Genetics Wilmington, DE, USA.
authors.forename: J Antoni
authors.initials: JA
authors.lastname: Rafalski
authors.affiliation: Genetic Discovery, DuPont Pioneer Johnston, IA, USA.
authors.forename: Kanwarpal
authors.initials: K
authors.lastname: Dhugga
authors.affiliation: Australian Centre for Plant Functional Genomics, School of Agriculture Food and Wine, University of Adelaide Adelaide, SA, Australia ; School of Agriculture, Food and Wine, University of Adelaide Adelaide, SA, Australia.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Tester
authors.affiliation: School of Agriculture, Food and Wine, University of Adelaide Adelaide, SA, Australia.
authors.forename: Brent N
authors.initials: BN
authors.lastname: Kaiser
keywords: N; NUE; Zea mays; ammonium; nitrate; nitrogen use efficiency; uptake