Variation in the effects of ethephon on flowering and extension growth in chrysanthemum as a function of temperature, season, and genetics

Involvement of the ethylene response pathway in dormancy induction in chrysanthemum

“…Ethylene biosynthesis can be altered by feedback effects of reduced ethylene sensitivity in transgenic lines. So ethephon was used as an ethylene-releasing agent, because ethylene evolution by decomposition of ethephon depends only on temperature in chrysanthemums ( Sumitomo et al , 2008 ). On the day of transfer into the growth chamber, all plants received one spray treatment of ethephon (to run-off) to all aerial parts at 0, 100, or 1000 mg l −1 Ethrel-10 (Ishihara Sangyo Kaisha Ltd, Osaka, Japan) and 0.025% (v/v) Triton X-100.…”

“…Seasonal changes in extension growth and flowering of this short-day (SD) herbaceous perennial are an adaptation to a temperate climate in middle latitudes. Growth and flowering depend on the combination of growing temperature, daylength, and the environment of the previous season ( Schwabe, 1950 , 1955 ; Sumitomo et al , 2008 ; T Hisamatsu, unpublished data). Temperature is significant, and the temperature of the previous season is an important factor in determining the capacity for growth and flowering in the subsequent season.…”

“…This decrease narrows the temperature range over which extension growth and flowering are possible ( Vegis, 1964 ), and chrysanthemum plants show slower extension growth and flowering in autumn than in spring at the same growing temperature ( Sumitomo et al , 2008 ; T Hisamatsu, unpublished data). For example, at growing temperatures of 15/10 °C (light/dark), ‘Sei-marine’ plants showed rapid extension and flowering in April (spring), but showed neither late in August (autumn) after exposure to high temperatures ( Sumitomo et al , 2008 ). Plants exposed to summer heat form rosettes by a cessation of elongation, never flower, and become dormant under subsequent cool temperature (<15 °C) in late autumn.…”

“…Rosette formation is the main adaptive response, maintaining the viability of meristems under winter cold, similar to the formation of terminal buds in woody perennials. In chrysanthemum, first high temperatures and then cool temperatures are significant environmental cues for the formation of rosettes before winter ( Schwabe, 1955 ; Sumitomo et al , 2008 ; T Hisamatsu, unpublished data).…”

“…Exogenous ethylene suppresses flower initiation and internode elongation in chrysanthemum ( Tjia et al , 1969 ), as does 2-chloroethylphosphonic acid (ethephon), which is hydrolysed and releases to ethylene in plant tissues ( Warner and Leopold, 1969 ; Kher et al , 1974 ; Cockshull and Horridge, 1978 ). Ethephon has been shown to induce rosette formation in chrysanthemum ( Sumitomo et al , 2008 ). In potato ( Solanum tuberosum ), ethylene has been shown to induce bud dormancy in microtubers, and the competitive ethylene antagonist 2,5-norbornadiene has been shown to promote microtuber sprouting ( Suttle, 1998 ).…”