A Synergistic Stimulation of Avena sativa Coleoptile Elongation by Indoleacetic Acid and Carbon Dioxide.

The ability of 0.03% CO(2) to stimulate growth has been investigated using etiolated Avena coleoptile sections maintained in buffered solution. This concentration of CO(2)-stimulated growth after a lag period of 12 to 15 minutes, and a synergistic relationship between indoleacetic acid and CO(2) in stimulating growth has been demonstrated. The response to CO(2) is inhibited by cycloheximide and is lost approximately 10 minutes after exposure to CO(2)-free air. Malate can replace CO(2) in stimulating growth. In the light of these data and recent literature on a growth response of coleoptile sections to CO(2)-saturated solutions, the existence of two mechanisms of CO(2)-simulated growth is proposed. In addition, it is suggested that growth promotion by 0.03% CO(2) is mediated by a process involving dark CO(2) fixation.