Effects of CO2 Enrichment on Plant Growth and Photosynthesis Properties of Paeonia ostii Cultivar ‘Feng Dan Bai’

The response of growth and the net leaf photosynthetic rate (Pn) of fouryearold pot grown plants of Paeonia ostii cultivar ‘Feng Dan Bai’ to high CO2 concentration in the topopen plastic chamber was studied by means of applying LI6400 photosynthesis system (LICOR). The results showed that the net leaf photosynthetic rate (Pn) of plants growing under (1000 ± 100)μmol/mol CO2 concentration (OTC1) and (700±100)μmol/mol CO2 concentration (OTC2) was both higher than that of the plants in the control group grown under ambient (400±50)μmol/mol CO2 concentration throughout the whole experiment period. Compared to the control, the average diurnal Pn of the plants in group OTC1 increased by 12578%, 13534%, 26110% and 23949% respectively after having been treated for 30d, 60d, 90d and 120d. The average diurnal Pn of the plants in group OTC2 increased by 7329%, 11771%, 71.01% and 73.02% compared to the control respectively after having been treated for 30d, 60d, 90d and 120d. After having been treated for 60d, the plant height, single leaf area, basal diameter, fresh weight and dry weight of the plants in group OTC1 was 8.61%, 16.68%, 2.56%, 9.48% and 9.63% higher than those of the control. After having been treated for 60d, the plant height, single leaf area, basal diameter, fresh weight and dry weight of the plants in group OTC2 was 4.12%, 6.35%, 0.64%, 5.56% and 7.08% higher than those of the control. After having been treated for 120d, the plant height, single leaf area, basal diameter, fresh weight and dry weight of the plants in group OTC1 was 8.41%, 9.64%, 2.50%, 14.76% and 9.20% higher than those of the control. After having been treated for 120d, the plant height, single leaf area, basal diameter, fresh weight and dry weight of the plants in group OTC2 was 5.88%, 12.90%, 1.87%, 10.52% and 7.78% higher than those of the control. With the increase of CO2 concentration, the stomatal conductance and transpiration rate of the Paeonia ostii cultivar ‘Feng Dan Bai’ seedlings decreased whereas the water use efficiency rose significantly.