title: Leaf angle responds to nitrogen supply in eucalypt seedlings. Is it a photoprotective mechanism?
abstract: We examined the adjustment of leaf angle (L theta) and foliar chlorophyll and xanthophyll chemistry in Eucalyptus nitens (Deane and Maiden) Maiden seedlings maintained in various nitrogen (N)-supply treatments over a 6-month period. Adjustment of L theta toward the vertical was greatest under conditions of foliar N deficiency and became incrementally more horizontal with increasing foliar N concentration. Photochemical efficiency (Fv/Fm) and quantum yield were lower in seedlings with low foliar N (low-N seedlings) in winter, but not in autumn. Low-N seedlings generally had low area-based chlorophyll concentrations and high xanthophyll-cycle conversion ratios, particularly during months of low temperature. Under mild temperature conditions, high concentrations of zeaxanthin and antheraxanthin were associated with lower electron transport rates (ETR). Incident light, Fv/Fm, ETR and total chlorophyll concentration were negatively correlated with L theta, with horizontal leaf orientation measured as 0 degrees and vertical leaf orientation as 90 degrees . Xanthophyll conversion ratio was positively correlated with L theta. Adjustments in L theta may play a role in photoprotection of E. nitens seedlings by assisting the leaf to balance its utilization and dissipation of energy.
authors.affiliation: Cooperative Research Centre for Sustainable Production Forestry, Private Bag 12, Hobart 7001, Australia. dclose@bgpa.wa.gov.au
authors.forename: Dugald C
authors.initials: DC
authors.lastname: Close
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Beadle
mesh_terms: D000064:Acclimatization; D002734:Chlorophyll / Q000378:metabolism; D005052:Eucalyptus / Q000033:anatomy & histology / Q000378:metabolism / Q000502:physiology*; D008027:Light; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves / Q000033:anatomy & histology / Q000378:metabolism / Q000502:physiology; D012621:Seasons; D036226:Seedlings / Q000378:metabolism / Q000502:physiology*; D024341:Xanthophylls / Q000378:metabolism
chemical_list: D024341:Xanthophylls; D002734:Chlorophyll; D009584:Nitrogen