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Nitrogen dynamics during O 3 ‐induced accelerated senescence in hybrid poplar
Author(s) -
Bielenberg D. G.,
Lynch J. P.,
Pell E. J.
Publication year - 2002
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.2002.00828.x
Subject(s) - shoot , nitrogen , cutting , horticulture , ozone , charcoal , senescence , chemistry , allometry , nitrogen cycle , botany , biology , ecology , organic chemistry , microbiology and biotechnology
Experiments were conducted to determine the fate of nitrogen (N) remobilized as a result of ozone (O 3 )‐induced accelerated senescence in hybrid poplar subjected to declining N availability concurrent with O 3 stress. Cuttings were grown in sand culture where the supply of N to the plant could be controlled on a daily basis and reduced in half of the plants when desired. Plants all initially received 3·57 m m N daily until approximately the 20 leaf stage after which daily supply of N was reduced to 0·71 m m . Plants were grown in open‐top chambers in the field (Rock Springs, PA, USA) and received charcoal‐filtered air, half also received supplemental O 3 to a level of 0·08 µL L −1 . Allocation of newly acquired N was determined with 15 N. The specific allocation (mg labelled N mg −1 total N) of labelled N to upper, expanding leaf N was not affected by O 3 , but was strongly affected by N treatment. However, O 3 increased the relative partitioning of labelled N to the expanding leaves and the roots. The balance between partitioning of newly acquired N to the upper leaves and roots was not affected by O 3 , but was reduced by N withdrawal. Calculated net N flux was strongly negative in the lower leaves of O 3 ‐exposed, N withdrawal plants. Nitrogen uptake was not reduced by O 3 . The allometric relationships between the roots and shoots were not affected by O 3 or N availability. The relative contribution of newly acquired versus remobilized N to new growth appears to be determined by N supply. Ozone exposure alters the allocation of newly acquired N via alterations in plant size, whereas N availability exerts a strong effect upon both plant size and N allocation.