Maturity and temperature influence ethylene-promoted organ abscission in Camellia

The influence of temperature (1-25 degrees C) and maturity on organ absciss ion promoted by a range of ethylene concentrations (0.3-100 mu l litre(-1)) was examined on stem explants of two Camellia cultivars ('Anticipation' an d 'Donation'; C. saluenensis x C. japonica). Time to abscission of 50% of l eaf and floral buds was measured. Leaves were most responsive during stem e longation following vegetative budbreak. In contrast, ethylene-responsivene ss of floral buds gradually increased with maturity. Low temperatures (1-5 degrees C) reduced the rate of abscission response to ethylene at all conce ntrations, but with greatest effect at low concentrations (<2 mu l litre(-1 )). Floral buds of both Camellia cultivars were more sensitive to ethylene than leaves. Application of a high ethylene concentration correctly determi ned relative abscission differences for maturity effects, but inter-organ d ifferences required a range of ethylene concentrations. It is proposed that "responsiveness" be defined as differences in abscission response to a hig h ethylene concentration (e.g. 10 mu l litre(-1)), whereas differences in a bscission response Ito low ethylene concentrations (<1 mu l litre(-1)) be d efined as "sensitivity" differences.