title: An analysis of the action of light on betalain synthesis in the seedling of Amaranthus caudatus, var. viridis.
abstract: Accumulation of betalain (amaranthin) in the seedling of Amaranthus caudatus, var. viridis, is inducible by light. Since the apparent lag-phase of amaranthin accumulation after the onset of light is of the order of 3 h, light induction experiments could be performed up to 3 h after the onset of light without interference with actual synthesis. The intricate induction phenomena can be explained as follows: The inductive light operates through phytochrome and through a blue/UV photoreceptor ('cryptochrome'). A phytochrome-dependent 'High Irradiance Reaction' is of minor importance. However, there is a strong, specific interaction between the light effects mediated through phytochrome and cryptochrome in the sense that the 'extent of the reversible response' - (response obtained with a particular light treatment terminated with a saturating red light pulse) minus (response obtained with the same light treatment when terminated with a saturating 756 nm light pulse) -increases with increasing Pfr level and total fluence rate during the induction period. It is concluded that light induced amaranthin synthesis is, in fact, a convenient biochemical model system of photomorphogenesis in the case when phytochrome and cryptochrome operate simultaneously in mediating photomorphogenesis.
authors.affiliation: Biologisches Institut II der Universität, Schänzlestraße 1, D-7800, Freiburg, Germany.
authors.forename: V K
authors.initials: VK
authors.lastname: Kochhar
authors.forename: S
authors.initials: S
authors.lastname: Kochhar
authors.forename: H
authors.initials: H
authors.lastname: Mohr