Carbon Dioxide as an Essential Requirement for Cultured Sycamore Cells

Carbon dioxide (optimum concentration c. 1.0%) is essential to the initiation of the growth in suspension culture or on agar plates of cultured sycamore cells. By effective flushing of the cultures with CO2‐free air it is possible to demonstrate this requirement with initial cell densities up to 50 × 103 cells ml−1. This growth‐promoting activity of carbon dioxide is not related to any effect it may have on the pH of the culture medium. The cells fix applied carbon dioxide into organic and amino acids but attempts to replace the carbon dioxide requirement by non‐toxic levels of organic or amino acids have not been successful.