Investigations on the role of ethylene in phytochrome-mediated photomorphogenesis : I. Anthocyanin Synthesis.

The etiolating, intact mustard (Sinapis alba L.) seedling exhibits a distinct temporal pattern of ethylene production. Light, operating through phytochrome, increases the rate of ethylene production without changing the pattern. Ethylene production of the isolated plant parts (segments), added together, exceed the production of the intact system even if the wound effect is taken into account. There is no significant light effect on ethylene production of the segments. Phytochrome-mediated anthocyanin synthesis in the cotyledons is inhibited by ethylene. The responsiveness towards ethylene of the anthocyanin producing metabolic chain is decreased by phytochrome. As anthocyanin synthesis is only partly inhibited under saturating ethylene concentrations in the atmosphere around the seedlings (100 μl l(-1)), a twofactor analysis becomes feasible. This analysis leads to the result that phytochrome and ethylene show multiplicative behavior, meaning that phytochrome and ethylene act on the same metabolic sequence (leading to anthocyanin) but independently of each other, and at different sites. Therefore, the hypothesis that ethylene mediates the action of phytochrome in anthocyanin synthesis and photomorphogenesis in general appears to be inapplicable.