RELATIONSHIP BETWEEN THE ACTIVITY OF THE ETHYLENE-FORMING ENZYME AND THE LEVEL OF INTRACELLULAR 2,4-DICHLOROPHENOXYACETIC ACID IN PEAR CELL-CULTURES INVITRO

Ethylene production by auxin-dependent pear cells cultured in vitro falls rapidly when they are deprived of 2,4-D. This phenomenon is associated with a decrease in ACC production. Readdition of 2,4-D causes a resumption of ACC production and ethylene synthesis. Ethylene-forming enzyme (EFE) activity, although never limiting, decreases sharply during 2,4-D depletion and rises again upon addition of 2,4-D. This increase in the EFE activity is not a rapid response to 2,4-D, since it requires several hours. Changes in EFE activity follow the same pattern as changes in 2,4-D concentration; the decrease in EFE activity is also concomitant with a decrease in the ability of 2,4-dinitrophenol to inhibit ethylene production. The possible role of auxins in the modulation of EFE activity is discussed. © 1991 Springer-Verlag New York Inc.