CO₂ Concentration Profiles in a Plant Tissue Culture Vessel

Abstract

Carbon dioxide concentration profiles in a test tube-type tissue culture vessel containing a plantlet cultured on sugar free medium were measured during the photoperiod. The CO₂ concentration at 70 mm below the lid was higher than that at 5 mm below the lid, and it decreased linearly with increasing the distance from the lid. When the photosysnthetic photon flux density (PPFD) was set at 20, 50, 80 or 140μmol m^-2 s^-1, the CO₂ concentration at 70 mm below the lid was 263, 150, 96 or 91μmol mol^-1, respectively, under a CO₂ concentration of 360μmol mol^-1 outside the vessel and an air temperature of 25°C inside the vessel. The CO₂ concentration difference inside the vessel between at 5 and 70 mm below the lid was 70, 137, 179 or 185μmol mol^-1, respectively, under the four levels of PPFD. When the CO₂ concentration outside the vessel was maintained 130, 340, 870, 1 890 or 2 570μmol mol^-1, the CO₂ concentration at 70 mm below the lid was 91, 104, 171, 363 or 770μmol mol^-1, respectively, under a PPFD of 110μmol m^-2 s^-1 and an air temperature of 25°C inside the vessel. The CO₂ concentration difference between at 5 and 70 mm below the lid was 27, 147, 477, 1 002 and 1216μmol mol^-1, respectively, under the five levels of CO₂ concentration outside the vessel. These results show that the CO₂ diffusion resistance inside the vessel is high and thus the net photosynthetic rate of the plantlet is restricted by low CO₂ concentration near the plantlet.