| Autor: |
Bielenberg, D. G, Lynch, J. P, Pell, E. J |
| Předmět: |
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| Zdroj: |
Plant, Cell & Environment; Apr2002, Vol. 25 Issue 4, p501-512, 12p |
| Abstrakt: |
Abstract Experiments were conducted to determine the fate of nitrogen (N) remobilized as a result of ozone (O3 )-induced accelerated senescence in hybrid poplar subjected to declining N availability concurrent with O3 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 mm N daily until approximately the 20 leaf stage after which daily supply of N was reduced to 0·71 mm. Plants were grown in open-top chambers in the field (Rock Springs, PA, USA) and received charcoal-filtered air, half also received supplemental O3 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 O3 , but was strongly affected by N treatment. However, O3 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 O3 , but was reduced by N withdrawal. Calculated net N flux was strongly negative in the lower leaves of O3 -exposed, N withdrawal plants. Nitrogen uptake was not reduced by O3 . The allometric relationships between the roots and shoots were not affected by O3 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. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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