title: Short-term physiological and developmental responses to nitrogen availability in hybrid poplar.
abstract: Nitrogen fertilization induces dramatic changes in the growth and development of plants, including forest trees. In this study we examined short-term responses of hybrid poplar, Populus balsamifera ssp. trichocarpa x deltoides, to N fertilization. Glasshouse-grown saplings subjected to limiting, intermediate, and luxuriant levels of ammonium nitrate over a 28 d time course demonstrated rapid changes to whole-plant architecture and biomass accumulation. Nitrogen-associated shifts in allocation occurred in temporally distinct stages. Nitrogen availability modulated parameters that affect carbon gain, including light-saturated net photosynthesis and leaf area. These parameters were affected by N-induced changes to leaf maturation and senescence. Leaf area was also affected by N-induced sylleptic branch development. Genes encoding vegetative storage proteins and starch biosynthetic enzymes exhibited contrasting patterns of expression under differential N availability. A gene encoding a previously uncharacterized putative pectin methylesterase inhibitor displayed expression patterns comparable to the starch biosynthetic genes. The results of this study illustrate the phenotypic plasticity that P. balsamifera ssp. trichocarpa x deltoides exhibits in response to differential N availability.
authors.affiliation: School of Forest Resources and Conservation, University of Florida, PO Box 110410, Gainesville FL 32611, USA. janice.cooke@ualberta.ca
authors.forename: Janice E K
authors.initials: JE
authors.lastname: Cooke
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Martin
authors.forename: John M
authors.initials: JM
authors.lastname: Davis
mesh_terms: D002244:Carbon / Q000378:metabolism; D003433:Crosses, Genetic; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism; D032107:Populus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D002244:Carbon; D009584:Nitrogen