EFFECTS OF CO₂ CONCENTRATION ON GROWTH AND PHOTOSYNTHESIS OF YOUNG TOMATO AND CARNATION PLANTS

Growth analysis and photosynthesis experiments were carried out with young tomato and carnation plants at different levels of CO₂ enrichment.
While raising the CO₂ concentration from ambient to 1000 ppm increases photosynthesis strongly in short term experiments, long term growth increases much less, 40–50% increase in photosynthesis versus less than 15% increase in Relative Growth Rate.

Two plant adaptations seem to be responsible for this discrepancy.
At higher CO₂ concentrations leaf thickness increases, which means a decrease in Leaf Area Ratio, an important parameter for growth of young plants.
Also photosynthesis decreases after prolonged CO₂ enrichment.
For carnation maximum photosynthesis decreases about 15% while carboxylation efficiency decreases about 40% after 8 weeks at 1000 ppm CO₂. For tomato these changes were of the same order of magnitude.
As there were no after-effects found on stomatal resistance for either tomato or carnation this effect may be explained as an increase in mesophyll or carboxylation resistance.

Symposium on CO2 Enrichment

G.T. Bruggink

https://doi.org/10.17660/ActaHortic.1984.162.32