Effects of CO2 enrichment on photosynthesis and growth in Gerbera jamesonii

• The interaction of CO2 and the physiological phenomenon “midday depression” has not been reported in Gerbera jamesonii.
• There were no significant physiological differences in plants between morning CO2 enrichment and daytime CO2 enrichment.
• CO2 enrichment improved the flower quality, mainly includes bigger and more flowers with longer stems.
• Morning CO2 enrichment exhibited greater cost savings in actual production.

Carbon dioxide (CO2) enrichment are widely reported to stimulate the plant growth. However, those relative studies in the horticultural plants are quite limited, particularly about the interaction of CO2 and the physiological phenomenon “midday depression”. Herein, daytime (T1, 7:00–19:00) and morning (T2, 7:00–12:00) CO2 enrichment treatments (800 ± 50 μmol mol−1) were conducted in open-top plastic greenhouses to investigate their effects on photosynthesis and growth in Gerbera jamesonii, compared to the atmospheric CO2 concentration (CK, approximately 400 μmol mol−1). The results showed that the leaf net photosynthetic rate (Pn) of G. jamesonii was averagely increased 52 ± 17% in T1 and 66 ± 8% in T2 by CO2 enrichment, which remarkably higher (P < 0.05) in T2 than that in T1 in the later period of the experiment (30–150 d). CO2 enrichment also significantly increased (P < 0.01) the contents of photoassimilates (soluble sugar, starch, and chlorophyll), but decreased the contents of soluble proteins (P < 0.05). The biomass determination in T1 and T2 revealed that plant dry weight was raised 40 ± 9% and 32 ± 6% on 150 days, respectively. In addition, CO2 enrichment enhanced the quantities and qualities of flowers (P < 0.05), such as augmented the flower number and size, extended the peduncle length, accumulated anthocyanin concentrations, and prolonged the flower vase life. Even though there were no significant differences between day and morning CO2 enrichment on the basis of the statistical data, the morning CO2 enrichment exhibited more favorable cost savings. According to these positive responses, we considered that the morning CO2 enrichment has a potential application in commential production of G. jamesonii.