A synthesis approach on the impact of elevated CO₂ on berry physiology and yield of Vitis vinifera

Besides the increase in global mean temperature the second main challenge of a changing climate is the increase in atmospheric carbon dioxide (CO2) in relation to physiology and yield performance of grapevines. The benefits of increasing CO2 levels under greenhouse environment or open field studies have been well investigated for various annual crops. Research under free carbon dioxide enrichment on field-grown perennial plants such as grapevines is limited to a few studies. Further, chamber and greenhouse experiments have been conducted mostly on potted vines under eCO2 conditions.

In this synthesis approach, the output of different CO2 enrichment experiments such as greenhouse and growth chamber trials will be compared to open top chamber (OTC) and Free Air Carbon dioxide Enrichment (FACE) studies. Furthermore, the regional climate in which single field studies have been conducted plays a major role in terms of up and down regulation of CO2 induced processes, whereas in open or closed chamber systems a stable but artificial microclimate exists within the chamber.

Due to higher photosynthesis rates under eCO2 mature field grown vines showed higher transport capacity and larger sinks for additional carbohydrates produced under eCO2, thus grapevines increased in vegetative and reproductive growth. During fruit ripening single berry weight, bunch architecture and bunch compactness altered similarly for vines under eCO2 within the field and to a lower extent when it comes to short-term chamber and greenhouse trials. Regarding crop yield, no or little differences occurred for all varieties for the first year of investigation. Usually, higher yield emerged under eCO2 in the following season as explained by the grapevine’s reproductive cycle. Analyses of berries and must resulted mostly in alterations of malic and tartaric acid concentrations under eCO2 and was close linked to berry size. Sugar accumulation in berries depended on climatic factors and differed if vines were grown under warm or cool climate conditions in combination with CO2 enrichment. Elevated CO2 was also des- cribed to modify some berry colour parameters like anthocyanins, but in the end both syntheses were induced – stimulation and inhabitation of anthocyanin accumulation.

Overall, eCO2 resulted in a change of vegetative, generative and qualitative parameters of grapevines compared to an atmospheric CO2 concentration without affecting wine quality in general. Nevertheless, as carbon dioxide is one of many influencing climate factors on fruit and berry development it needs to be discussed within the context of future wine quality.