© 2006 Heron Publishing—Victoria, Canada
Leaf angle responds to nitrogen supply in eucalypt seedlings. Is it a photoprotective mechanism?
Dugald C. Close (1, 2, 3, 4) and Christopher L. Beadle (1, 5)
1. Cooperative Research Centre for Sustainable Production Forestry, Private Bag 12, Hobart 7001, Australia / 2. Schools of Agricultural and Plant Science and Zoology, University of Tasmania, Private Bag 12, Hobart 7001, Australia / 3. Botanic Gardens and Parks Authority, Science Directorate, Fraser Avenue, West Perth, Perth 6005, Australia / 4. Corresponding author (dclose@bgpa.wa.gov.au) / 5. CSIRO Forestry and Forest Products, Private Bag 12, Hobart 7001, Australia / Received June 1, 2005; accepted August 27, 2005; published online March 1, 2006
Summary
We examined the adjustment of leaf angle (Lθ) 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 Lθ 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 Lθ, with horizontal leaf orientation measured as 0° and vertical leaf orientation as 90°. Xanthophyll conversion ratio was positively
correlated with Lθ. Adjustments in Lθ may play a role in photoprotection of E. nitens seedlings by assisting the leaf to balance its utilization and dissipation of energy.
Keywords:
acclimation, heliotropic, low temperature, photochemical efficiency, photoinhibition, seasonal, sustained xanthophyll engagement.
