title: Dynamics of light and nitrogen distribution during grain filling within wheat canopy.
abstract: In monocarpic species, during the reproductive stage the growing grains represent a strong sink for nitrogen (N) and trigger N remobilization from the vegetative organs, which decreases canopy photosynthesis and accelerates leaf senescence. The spatiotemporal distribution of N in a reproductive canopy has not been described in detail. Here, we investigated the role of the local light environment on the spatiotemporal distribution of leaf lamina N mass per unit leaf area (SLN) during grain filling of field-grown wheat (Triticum aestivum). In addition, in order to provide some insight into the coordination of N depletion between the different vegetative organs, N dynamics were studied for individual leaf laminae, leaf sheaths, internodes, and chaff of the top fertile culms. At the canopy scale, SLN distribution paralleled the light gradient below the flag leaf collar until almost the end of grain filling. On the contrary, the significant light gradient along the flag leaf lamina was not associated with a SLN gradient. Within the top fertile culms, the time course of total (alive + necrotic tissues) N concentration of the different laminae and sheaths displayed a similar pattern. Another common pattern was observed for internodes and chaff. During the period of no root N uptake, N depletion of individual laminae and sheaths followed a first-order kinetics independent of leaf age, genotype, or N nutrition. The results presented here show that during grain filling, N dynamics are integrated at the culm scale and strongly depend on the local light conditions determined by the canopy structure.
authors.affiliation: INRA, UMR 1091 Environnement et Grandes Cultures, F-78 850 Thiverval-Grignon, France.
authors.forename: Jessica
authors.initials: J
authors.lastname: Bertheloot
authors.forename: Pierre
authors.initials: P
authors.lastname: Martre
authors.forename: Bruno
authors.initials: B
authors.lastname: Andrieu
mesh_terms: D008027:Light; D009584:Nitrogen / Q000378:metabolism*; D014908:Triticum / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology
chemical_list: D009584:Nitrogen
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