In two subsequent years, an early maturing potato cultivar with low leaf area
index (LAI) and a late cultivar with high LAI were grown at concentrations of
350 and 700 L CO2 L–1 in
open-top chambers. The average increase of tuber dry matter yield by elevated
CO2 was 27% in 1995 and 49% in 1996.
During the first weeks after planting, elevated CO2
stimulated the light-saturated rate of photosynthesis
(Amax) of both cultivars by
80%. However, Amax under
elevated CO2 declined to the level of the
low-CO2 treatment in the course of the growing season.
In 1995 this convergence due to acclimation of photosynthesis was completed
within 6 weeks, but in 1996, acclimation proceeded until the end of the
growing season. Photosynthetic acclimation was accompanied by a reduced
Rubisco content, and was correlated more closely with accumulation of sucrose
than of starch. From fluorescence measurements it was concluded that, in
contrast to the carboxylation efficiency, the efficiency of photosynthetic
reactions centers was not affected by acclimation to elevated
CO2. The faster photosynthetic acclimation in 1995
coincided with overall lower values of
Amax, crop growth rate and growth
response to elevated CO2. It is shown that the
indeterminate growth pattern of potato with its large sink capacity does not
preclude acclimation. The effect of acclimation on yield was quantified by
computer simulations. The simulated results indicated that photosynthetic
acclimation reduced the positive effect of elevated CO2
on tuber yield by 50%.
Photosynthetic acclimation to elevated CO2 is modified by source:sink balance in three component species of chalk grassland swards grown in a free air carbon dioxide enrichment (FACE) experiment
