THE EFFECT OF ETHEPHON AND CHLORMEQUAT ON FLOWERING IN RHIPSALIDOPSIS GAERTNERI AND THE ZYGOCACTUS HYBRID, ‘WEIHNACHTSFREUDE’

Rooted cuttings of Rhipsalidopsis gaertneri and Zygocactus truncatus ‘Weihnachtsfreude’ were planted at the beginning of May and grown throughout the summer under long daylight conditions at a temperature of 20 °C. During the growth period, chlormequat (40 mg/plant) and ethephon (10 mg/plant) were applied to the plants.
The application was repeated when the plants were exposed to experimental conditions, on October 19th.

Ethephon restricted the increase of terminal shoots at the growth flash following the application of the growth regulators in Rhipsalidopsis, but not in Zygocactus.
Chlormequat, on the hand, increased the growth of terminals in both species of cacti but only under experimental conditions which did not promote Flower bud formation significantly.

Rhipsalidopsis plants failed to flower before Christmas under all experimental treatments.
This was also true of Zygocactus grown at 20 °C under natural short daylight conditions.
In the Zygocactus plants which did flower before Christmas, the percentage of flowering terminals was increased by chlormequat in plants exposed to 8 hour photoperiods and kept at a low temperature, but the total number of flower buds increased only at a low temperature (10 °C).

When the experiment was continued with Rhipsalidopsis, after the plants had been exposed to a temperature of 8 °C for 50 days, ethephon restricted and delayed flowering regardless of the temperature, whereas the effect of chlormequat on the percentage of flowering terminals was insignificant, though the number of buds below the terminal was increased and the number of days to flowering reduced by it under the low temperature treatment (10 °C).

Symposium on Growth Regulators in Floriculture

E. Kaukovirta

https://doi.org/10.17660/ActaHortic.1979.91.51