180-2 Reduced Nitrogen Fertility Accelerates the Stimulation of Senescence Caused By Chronic Ozone In Nicotiana sylvestris.

See more from this Division: Special Sessions
See more from this Session: Nitrogen-Climate Interactions and Soil Processes
Tuesday, October 23, 2012: 1:35 PM
Duke Energy Convention Center, Room 233, Level 2
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Craig Yendrek1, Courtney P. Liesner2 and Elizabeth Ainsworth1, (1)USDA-ARS Global Change and Photosynthesis Research Unit, Urbana, IL
(2)University of Illinois, Urbana, IL
Tropospheric ozone (O3) is a damaging air pollutant that has been estimated to cost U.S. growers over $1.7 to 3.8 billion per year. Growth in chronic elevated ozone leads to reductions in chlorophyll, photosynthetic capacity and leaf longevity, all of which have a negative impact on yield.  Here, we compared sequential cohorts of leaves in tobacco (Nicotiana sylvestris) that when grown in elevated O3 with limiting nitrogen (N), revealed major decreases in photosynthetic parameters for the older leaf, including a 55% decrease in CO2 assimilation, 57% decrease in stomatal conductance, 49% decrease in maximum carboxylation rate and 41% decrease in photosynthetic electron transport. Unexpectedly, an increase in shoot N content was observed in these leaves. As no change in root N content was observed between plants grown in limiting N and either ambient or elevated O3, this indicates that N recycling to young leaves was induced by O3-stimulated senescence. Up-regulation of senescence-related transcripts, as determined by qRT-PCR, confirmed that elevated O3 caused the older cohort of leaves to enter senescence sooner and had progressed through senescence at a faster rate. While sufficient N was able to prevent the onset of senescence in elevated O3, root N content was decreased, implying that N was diverted from root development in order to sustain normal metabolic rates at the leaf level. This works suggests that as O3 levels continue to increase, crops will become more sensitive in fields with poor N fertility.
See more from this Division: Special Sessions
See more from this Session: Nitrogen-Climate Interactions and Soil Processes