Ethylene production in habituated and auxin-requiring tobacco callus cultures. Does ethylene play a role in the habituation?

Ethylene production of habituated and auxin-requiring tobacco (Nicotiana tabacum L. cv. Xanthi) callus cultures were compared. More ethylene was produced by auxinrequiring i.e. auxin-heterotrophic cultures than by habituated ones. Treatment with 2,4-dichlorophenoxyacetic acid increased the ethylene evolution of habituated cultures over the range 10−7 to 10−4M, which suggests that the higher ethylene production of auxin-dependent callus is caused by the 2,4-D in the medium. The IAA levels depended on the age of both types of callus cultures.