Bielenberg, D.G.; Lynch, J.P.; Pell, E.J.


New Phytologist, Blackwell Science, Volume 151, Issue 2, UK, p.413-425 (2001)

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The effects of a decline in nitrogen (N) availability on ozone (O 3 )-induced accelerated foliar senescence during the growing season in a hybrid poplar are presented. Cuttings of Populus trichocarpa x maximowizii were grown in sand culture where N supply to the plant could be controlled on a daily basis and reduced in half of the plants when desired. All plants received charcoal-filtered air; half also received supplemental O 3 . Ozone and N withdrawal both reduced plant growth. Plants grown in both N treatments displayed leaf senescence and abscission in response to O 3 , but leaf abscission in the N-withdrawal treatment was approximately double that of the constant-N treatment. Ozone had differential effects on light-saturated net photosynthesis (A sat ) and total soluble protein in the younger and older foliage depending on N treatment. A decline in N availability increased the rate of O 3 -induced accelerated senescence and was associated with plant size and possibly continued active growth. Compensatory responses of young leaves to O 3 exposure only occurred when N availability to the plant declined and O 3 -induced accelerated senescence was most severe.