title: N-fertilization has different effects on the growth, carbon and nitrogen physiology, and wood properties of slow- and fast-growing Populus species.
abstract: To investigate how N-fertilization affects the growth, carbon and nitrogen (N) physiology, and wood properties of poplars with contrasting growth characteristics, slow-growing (Populus popularis, Pp) and fast-growing (P. alba×P. glandulosa, Pg) poplar saplings were exposed to different N levels. Above-ground biomass, leaf area, photosynthetic rates (A), instantaneous photosynthetic nitrogen use efficiency (PNUE (i)), chlorophyll and foliar sugar concentrations were higher in Pg than in Pp. Foliar nitrate reductase (NR) activities and root glutamate synthase (GOGAT) activities were higher in Pg than in Pp as were the N amount and NUE of new shoots. Lignin contents and calorific values of Pg wood were less than that of Pp wood. N-fertilization reduced root biomass of Pg more than of Pp, but increased leaf biomass, leaf area, A, and PNUE(i) of Pg more than of Pp. Among 13 genes involved in the transport of ammonium or nitrate or in N assimilation, transcripts showed more pronounced changes to N-fertilization in Pg than in Pp. Increases in NR activities and N contents due to N-fertilization were larger in Pg than in Pp. In both species, N-fertilization resulted in lower calorific values as well as shorter and wider vessel elements/fibres. These results suggest that growth, carbon and N physiology, and wood properties are more sensitive to increasing N availability in fast-growing poplars than in slow-growing ones, which is probably due to prioritized resource allocation to the leaves and accelerated N physiological processes in fast-growing poplars under higher N levels.
authors.affiliation: Key Laboratory of Applied Entomology, College of Plant Protection, Northwest Agriculture and Forestry University, Yangling, Shaanxi, 712100,  PR China.
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Mengchun
authors.initials: M
authors.lastname: Li
authors.forename: Jie
authors.initials: J
authors.lastname: Luo
authors.forename: Xu
authors.initials: X
authors.lastname: Cao
authors.forename: Long
authors.initials: L
authors.lastname: Qu
authors.forename: Ying
authors.initials: Y
authors.lastname: Gai
authors.forename: Xiangning
authors.initials: X
authors.lastname: Jiang
authors.forename: Tongxian
authors.initials: T
authors.lastname: Liu
authors.forename: Hua
authors.initials: H
authors.lastname: Bai
authors.forename: Dennis
authors.initials: D
authors.lastname: Janz
authors.forename: Andrea
authors.initials: A
authors.lastname: Polle
authors.forename: Changhui
authors.initials: C
authors.lastname: Peng
authors.forename: Zhi-Bin
authors.initials: ZB
authors.lastname: Luo
mesh_terms: D001692:Biological Transport; D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D005970:Glutamate Synthase / Q000378:metabolism; D008031:Lignin / Q000032:analysis; D050901:Nitrate Reductase / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000502:physiology / Q000648:ultrastructure; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000502:physiology / Q000648:ultrastructure; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development / Q000502:physiology / Q000648:ultrastructure; D018547:Plant Stems / Q000235:genetics / Q000254:growth & development / Q000502:physiology / Q000648:ultrastructure; D018526:Plant Transpiration / Q000502:physiology; D032107:Populus / Q000235:genetics / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012987:Soil; D013045:Species Specificity; D014934:Wood / Q000254:growth & development*; D052584:Xylem / Q000235:genetics / Q000254:growth & development / Q000502:physiology / Q000648:ultrastructure
chemical_list: D009566:Nitrates; D010940:Plant Proteins; D000644:Quaternary Ammonium Compounds; D012987:Soil; D002244:Carbon; D008031:Lignin; D005970:Glutamate Synthase; D050901:Nitrate Reductase; D009584:Nitrogen