Delaying the biosynthesis of aromatic secondary metabolites in postharvest strawberry fruit exposed to elevated CO2 atmosphere.

Aromatic secondary metabolites are closely related to quality attributes of postharvest fruit. In the present study, 20% CO₂ was applied to strawberry fruit to investigate the regulation of elevated CO₂ on aromatic secondary metabolites. The results showed that elevated CO₂ delayed accumulations of anthocyanins, eugenol and lignin. Phenylalanine and tyrosine, the precursors of the above secondary metabolites, were 18.90% and 35.61%, respectively, lower in CO₂-treated fruit compared with the control on day 6. Furthermore, enzyme activities and transcriptional profiles analysis showed pentose phosphate pathway and glycolysis were activated by elevated CO₂ whereas the aromatic amino acids (AAAs) pathway was inhibited. These results indicated that elevated CO₂ restricted carbon flux into aromatic secondary metabolism by inhibiting the AAAs pathway, leading to the decrease of phenylalanine and tyrosine, and thus, delayed the accumulation of aromatic secondary metabolites. In addition, the effect of elevated CO₂ was eliminated after transferred CO₂-treated fruit to air.