Rac. Mitchell et al., Is there scope for improving balance between RuBP-regeneration and carboxylation capacities in wheat at elevated CO2?, J EXP BOT, 51, 2000, pp. 391-397
Carboxylation and RuBP-regeneration capacities, which determine light-satur
ated photosynthetic rate, were analysed in leaves of spring wheat (Triticum
aestivum L, cv, Minaret) grown under different atmospheric CO2 partial pre
ssure (pC(a)) and N supply regimes. Capacities were estimated from a large
number of gas exchange, Rubisco and ATP-synthase content measurements, and
from these, the pC(a) at which the two capacities are equal was derived, to
allow direct comparison with growth pC(a). Acclimation of the balance betw
een the two capacities to growth at elevated pC(a) in wheat was only partia
l and appears to occur mostly in older flag leaves and at low N, However, i
n contrast to conclusions drawn from previous analyses of these data, there
was evidence of a specific effect of growth at 70 Pa pC(a), where carboxyl
ation capacity is reduced more than RuBP-regeneration capacity for a given
leaf N content. A model was used to estimate the effects of fluctuations in
PPFD and temperature in the growth environment on the optimal balance betw
een these capacities, This showed that the observed balance between carboxy
lation and RuBP-regeneration capacities in young wheat leaves could be cons
istent with adaptation to the current, or even the preindustrial pC(a).