1985 Volume 54 Issue 1 Pages 87-93
Effects of the concentration of 2-chloroethyl-phosphonic acid (ethephon) and its application frequency on stem elongation and flower formation in chrysanthemum plants were studied. It was also investigated whether the ethephon simply inhibits the stem elongation for its active period or it induces rosette formation.
When an aqueous solution of ethephon at 1, 000ppm or higher was applied 3 times at 7 day intervals, a strong inhibition of the stem elongation and flower formation was observed.
Elongation of the plants was inhibited only for a short period when high concentration of ethephon was treated in spring and summer, and then the stems started to elongate about 15 days after the last ethephon applications. In contrast, the plants treated in September stopped elongation and remained rosette form untill the following spring.
The ethephon application in late August or earlier did not induce the rosette formation even in short day and cool conditions. The rosette formation was induced only when ethephon was applied later than early September.
It appears that ethephon or ethylene lowers the growth activity and induces the rosette formation in chrysanthemum plants which have experienced high temperature in summer.