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 1,015 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 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, sulfur, copper, and manganese were not affected by eCO₂. Furthermore, we propose several approaches to improving vegetable quality based on the interaction of eCO₂ with various factors, including species, cultivars, CO₂ levels, growth stages, light, O₃ stress, nutrient, and salinity. Finally, we present a summary of the eCO₂ impact on the quality of three widely cultivated crops, namely, lettuce, tomato, and potato.