Table 3: Effect of increased CO₂ concentrations on physical and chemical properties of strawberry fruit.

CO2 concentrations	Observations in strawberry fruit due to increased CO2 levels	Reference
Ambient + 300 ppm Ambient + 600 ppm 353/400 to 600 ppm day/and night	Increased fruit dry matter contents by 18% with extra 300 ppm and 39% at extra 600 ppm CO2. Increased total sugar by 12% in air enriched with 300 ppm and 20% in air enriched with 600 ppm due to increased net photoassimilate production Increased sweetness due to increased sugar contents. Increased organic acids in fruits grown at ambient plus 600 ppm to 17.4% as compared to 8.4% at ambient plus 300 ppm. Reduced sourness of fruit. Enhanced levels of flavor compounds in fruit including ethyl hexanoate, ethyl butanoate and methyl hexanoate as increased sugars act as precursors for flavor compounds.	Wang and Bunce [15]
Ambient + 300 ppm Ambient + 600 ppm 353/400 to 600 ppm day/and night	Enhanced ascorbic acid content by 10% at ambient + 300 ppm and 13% at ambient + 600 ppm and decreased dehydroascorbic acid content thereby increased the AA/DHA ratio. Increased glutathione (GSH) by 171% at ambient + 600 ppm and GSH/GSSG (oxidized GSH) ratio. Yielded significantly higher anthocyanins and flavonoid, content. Increased oxygen radical absorbance activity in fruit of strawberry plants grown in the CO2 enrichment conditions.	Wang, et al. [41]
390 ppm (ambient) 560 ppm	Increased yield by 17% to 42% due to increased carbohydrate accumulation, total fresh fruit weight, and flower and fruit number per plant.	Deng and Woodward [31]
300 ppm, 450, 600, 750, and 900 ppm	Increased average fruit yield per plant by 0.7, 2.7, 3.6, and 4.1-fold, daily growth per fresh fruit by 0.4, 1.0, 1.1, and 1.3-fold, and growth rate of fruit biomass per plant by 1.0, 3.9, 5.5, and 6.9-fold. Enhanced fruit development and branch-crown and pedicel development and flower bud differentiation. Enhanced fruit productivity through increased pedicel number per plant, fruit setting per pedicel, fruit size and dry matter content of the fruits. Increased total sugar content of fruits with higher sugar/acid ratio due to decreased titratable acid content. Promoted early and prolonged flowering and fruiting period.	Chen, et al. [36-38]
400, 600, and 900 ppm	Increased yield by 15%, 20%, and 31% at 400 ppm, 600 ppm and 900 ppm respectively due to increased fruit weight with shorter fruit development time.	Lieten [33]
340 ppm 1000 ppm	Increased fruit yield by 47% due to increased fruit set per plant.	Sung and Chen [34]