The effect of elevated CO2 concentrations on leaf carbohydrate, chlorophyll contents and photosynthesis in radish

The objective of this study was to evaluate the effect of different CO, concentrations on carbohydrate, chlorophyll contents and net photosynthetic productivity in radish (Raphanus sativus L., cv. Zara) leaves. Plants were exposed to 350, 700, 1,500 and 3,000 ppm atmospheric CO2 concentrations over ten days. Day/night temperature was 24 degrees C/17 degrees C and photoperiod was 16 h. Carbohydrate (fructose, glucose, sucrose and maltose) content analysis was performed using chromatographic methods. The content of chlorophyll was evaluated spectrophotometrically. The results showed that elevated CO2 increases total carbohydrate content and changes in hexoses/sucrose ratio. A significant increase in chlorophyll content was only in 1,500 ppm treatment. Differences in photosynthetic productivity rate were within error margins. There was no effect on carbohydrate and chlorophyll contents in radish leaves seven days after returning plants to ambient CO2, though higher photosynthetic productivity rate was in radish, previously grown under 700 ppm CO2. In summary, leaf carbohydrate contents affect the intensity of photosynthetic pigment synthesis.