Ethylene-insensitive floral senescence in Sandersonia aurantiaca (Hook)

We have demonstrated that the senescence of Sandersonia aurantiaca (Hook.) flowers is insensitive to ethylene. Treating detached, physiologically mature flowers with propylene (0.5%, 24 h) did not alter the patterns of colour change, fresh weight, or respiration which normally occur as the flowers senesce. Silver thiosulphate (STS, 1 mM) did not extend the vase life of the flowers. Postharvest ethylene production by flowers was negligible, regardless of whether they had been exposed to propylene and or STS. Cycloheximide treatments (1 mu M, 100 mu M) inhibited the loss of pigment or fading associated with flower senescence. This suggests that de novo protein synthesis is required for pigment degradation in senescing sandersonia flowers. However, 100 mu M cycloheximide also caused detached flowers to wilt prematurely, thereby changing the normal sequence of events that occur during senescence in this flower. Exposing flowers to actinomycin D caused a subtle change in their pattern of senescence and in vitro translation of RNA extracted from the flowers produced a pattern of translation products that differed from that of control flowers held in water. The data demonstrate that specific changes in both transcription and translation accompany the ethylene-insensitive senescence of sandersonia flowers.