Effects of Elevated CO2 on Nutritional Quality of Vegetables: A Review

Elevated atmospheric CO2 (eCO2) enhances the yield of vegetables and could also affect their nutritional quality. We conducted a meta-analysis using 57 articles consisting of 1015 observations and found that eCO2 increased the concentrations of fructose, glucose, total soluble sugar, total antioxidant capacity, total phenols, total flavonoids, ascorbic acid and calcium (Ca) in the edible part of vegetables by 14.2%, 13.2%, 17.5%, 59.0%, 8.9%, 45.5%, 9.5% and 8.2%, respectively, but decreased the concentrations of protein, nitrate, magnesium, iron and zinc by 9.5%, 18.0%, 9.2%, 16.0% and 9.4%. The concentrations of titratable acidity, total chlorophyll, carotenoids, lycopene, anthocyanins, phosphorus, potassium, sulphur, copper and manganese were not affected by eCO2. Furthermore, we propose several approaches to improve vegetable quality based on the interaction of eCO2 with factors, i.e. species, cultivars, CO2 levels, growth stages, light, O3 stress, nutrient and salinity. Finally, we give a summary of the eCO2-effect on quality of three widely-cultivated vegetables, i.e. lettuce, tomato and potato.