THE INFLUENCE OF CARBON DIOXIDE CONCENTRATION DURING HIGH-TEMPERATURE PERIODS ON NET PHOTOSYNTHESIS OF CUT ROSES

The aim of this study was to examine the effect of CO₂ concentration on net photosynthesis during 6-h periods of high temperatures in small stands of cut roses.
In a first experiment, net photosynthesis decreased to zero when the temperature was raised from 22°C to 32°C, when the CO₂ concentration was lowered from 800 to 380 µmol mol^-1 and photon flux density (PFD) was kept constant.
If the CO₂ concentration was held high, only a small reduction in photosynthesis took place with this temperature increase.
In a second experiment, the PFD in one plant stand was increased from 200 to 800 µmol m^-2 s^-1 and the temperature was raised from 20°C to 32°C while maintaining CO₂ at 800 µmol mol^-1. In another stand, the CO2 concentration was lowered to 380 µmol mol^-1 while the temperature was kept at 22°C — the combination of high temperature and high CO₂ concentration producing a much higher photosynthesis rate (50%) than low temperature/low CO₂. In a third experiment, three combinations of temperature and CO₂ concentration were studied during the period of high PFD. A temperature increase to 32°C, with CO₂ maintained at 800 µmol mol^-1, resulted in much higher photosynthesis rates than a temperature increase to 24°C when CO₂ concentration was decreased from 800 to 380 µmol mol^-1. On increasing the temperature to 37°C while keeping CO₂ concentration at 800 µmol mol^-1, photosynthesis rates fell between the other two treatments.
The results are discussed in relation to climate control strategies in greenhouses in order to maximize photosynthesis and light-use efficiency of roses.

V International Symposium on Artificial Lighting in Horticulture

L.M. Mortensen, H.R. Gislerod

CO₂ concentration, cut roses, net photosynthesis, photon flux density, temperature

https://doi.org/10.17660/ActaHortic.2006.711.8