Auxin-Autotrophie und Chromosomenzahl

Summary

Four strains of tobacco callus culture were investigated karyologically. These cultures were started by Gautheret. Two of them are auxin-autotrophic, the one, Tc, was induced by Agrobacterium tumefaciens to a crowngall tumor, the other, Ta, originated by habituation. The cultures of these strains were started in 1946. The two “normal” strains (Tn₁ and Tn₂) are auxinheterotrophic. They date back to 1961.

All four strains are polyploid. In each of the cultures there exist more than one level of ploidy; i.e., they are mixoploids to a greater or lesser degree.

A change in the composition of the culture medium with respect to auxin-kinetin-content alters the distribution of the different grades of ploidy in the cell-populations. However, the four cultures do not respond in the same way to a particular modification of the substrate.

The strains Tn₁ and Tn₂, which are heterotrophic for growth substances, are mainly tetraploid. The autotrophs Ta and Tc, which grow as tumors after transplantation on healthy plants, are mainly triploid.

The discussion of this result together with those of FOX renders it probable, that the correlation of the approximately triploid chromosome number to auxin-autotrophy after a prolonged culture period is a real one. According to subsequent discussions together with the findings of other workers and under consideration of regenerated plants from auxin-autotrophic cultures (to be described later) it seems more probable but not definitively proofed that triploidy is a result and not the cause of auxin-autotrophy.