title: Acclimation of leaf nitrogen to vertical light gradient at anthesis in wheat is a whole-plant process that scales with the size of the canopy.
abstract: Vertical leaf nitrogen (N) gradient within a canopy is classically considered as a key adaptation to the local light environment that would tend to maximize canopy photosynthesis. We studied the vertical leaf N gradient with respect to the light gradient for wheat (Triticum aestivum) canopies with the aims of quantifying its modulation by crop N status and genetic variability and analyzing its ecophysiological determinants. The vertical distribution of leaf N and light was analyzed at anthesis for 16 cultivars grown in the field in two consecutive seasons under two levels of N. The N extinction coefficient with respect to light (b) varied with N supply and cultivar. Interestingly, a scaling relationship was observed between b and the size of the canopy for all the cultivars in the different environmental conditions. The scaling coefficient of the b-green area index relationship differed among cultivars, suggesting that cultivars could be more or less adapted to low-productivity environments. We conclude that the acclimation of the leaf N gradient to the light gradient is a whole-plant process that depends on canopy size. This study demonstrates that modeling leaf N distribution and canopy expansion based on the assumption that leaf N distribution parallels that of the light is inappropriate. We provide a robust relationship accounting for vertical leaf N gradient with respect to vertical light gradient as a function of canopy size.
authors.affiliation: Unité Mixte Recherche 1095 Genetics, Diversity, and Ecophysiology of Cereals, Institut National de la Recherche Agronomique, F-63039 Clermont-Ferrand, Cedex 02, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Moreau
authors.forename: Vincent
authors.initials: V
authors.lastname: Allard
authors.forename: Oorbessy
authors.initials: O
authors.lastname: Gaju
authors.forename: Jacques
authors.initials: J
authors.lastname: Le Gouis
authors.forename: M John
authors.initials: MJ
authors.lastname: Foulkes
authors.forename: Pierre
authors.initials: P
authors.lastname: Martre
mesh_terms: D000064:Acclimatization / Q000502:physiology* / Q000528:radiation effects; D018556:Crops, Agricultural / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D016014:Linear Models; D009584:Nitrogen / Q000378:metabolism*; D009929:Organ Size / Q000528:radiation effects; D017785:Photons; D010788:Photosynthesis / Q000528:radiation effects; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000502:physiology* / Q000528:radiation effects; D014908:Triticum / Q000254:growth & development* / Q000528:radiation effects*
chemical_list: D009584:Nitrogen