Journal of Experimental Botany, Vol 49, 1999-2011, Copyright © 1998 by Oxford University Press
C Reid, E Fiscus and K Burkey
Content and activity of Rubisco and concentrations of leaf nitrogen,
chlorophyll and total non-structural carbohydrates
(TNC) were determined at regular intervals during the
1993 and 1994 growing seasons to understand the effects and interactions of
[O3] and elevated [CO2] on biochemical limitations to photosynthesis during
ontogeny. Soybean (Glycine max var. Essex) was grown
in open-top field chambers in either charcoal-filtered air (CF, 20 nmol
mol-1) or non-filtered air supplemented with 1.5 x
ambient [O3] (c. 80 nmol mol-1) at ambient (AA, 360
ARTICLES
Combined effects of chronic ozone and elevated CO2 on Rubisco activity and leaf components in soybean Glycine max
Department of Crop Science, Agricultural Research Service, Box 7632, North Carolina State University, Raleigh, NC 27695, USA; US Department of Agriculture Research Service, and Department of Crops Science, North Carolina State University, 3908 Inwood Road, Raleigh, NC 27603, USA; Corresponding author e-mail: chantal@arrc.ncsu.edu
mol mol-1) or elevated
[CO2] (700 mol mol-1).
Sampling period significantly affected all the variables examined. Changes
included a decrease in the activity and content of Rubisco during seed
maturation, and increased nitrogen (N), leaf mass per
unit area (LMA) and total non-structural carbohydrates
(TNC, including starch and sucrose) through the
reproductive phases. Ontogenetic changes were most rapid in O2-treated
plants. At ambient [CO2], O3 decreased initial activity (14-64% per unit
leaf area and 14-29% per unit Rubisco) and content of Rubisco (9-53%), and
N content per unit leaf area. Ozone decreased
LMA by 17-28% of plants in CF-AA at the end of the
growing season because of a 24-41% decrease in starch and a 59-80% decrease
in sucrose. In general, elevated CO2], in CF or O3-fumigated air, reduced
the initial activity of Rubisco and activation state while having little
effect on Rubisco content, N and the chlorophyll
content, per unit leaf area. Elevated CO2 decreased Rubisco activity by
14-34% per unit leaf area and 15-25% per unit Rubisco content of plants in
grown CF-AA, nd increases LMA by 27-74% of the leaf
mass per unit area in CF-AA because of a 23-148% increase in starch.
However, the data suggest that, at elevated [CO2], increases in starch and
sucrose are not directly responsible for the deactivation of Rubisco. Also,
there was little evidence of an adjustment of Rubisco activity in response
to starch and sucrose metabolism. Significant interactions between elevated
[CO2] and [O3] on all variables examined generally resulted in alleviation
or amelioration of the O3 effects at elevated CO2. These data provide
further support to the idea that elevated atmospheric CO2 will reduce or
prevent damage from pollutant O3.Key words: O3 x CO2
interaction, carbohydrate metabolism, Rubisco, sugars, nonstructural
carbohydrates.
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