NO REGULATION OF (45)CALCIUM-UPTAKE OR RELEASE BY PHYTOCHROME AS AN ESSENTIAL STEP IN THE TRANSDUCTION CHAIN

Induction of germination in spores of Dryopteris paleacea and in turio ns of Spirodela polyrhiza is phytochrome mediated. The presence of Ca2 + in the culture medium is required in both cases during a defined per iod after red light (R). To understand the role of Ca2+ in the phytoch rome-mediated response Ca-45-uptake into cells (R-irradiated or non-ir radiated) was investigated. Ca-45-uptake into turions occurred under a ll conditions tested, but was not significantly altered by R. Moreover , the release of Ca-45 from turions into a Ca2+-free medium was not af fected by R. Corresponding results were found in case of the single-ce lled spores. Furthermore, the Ca2+-antagonists La3+ and Co2+ reduced t he Ca-45-uptake into spores strongly. The results indicate that uptake as well as release of Ca2+ depend on the Ca2+-gradient established on both sides of the plasmalemma. It is concluded that calcium uptake or release is not an essential step within the phytochrome-induced chain of events, rather calcium has to be considered as a prerequisite (per missive factor) in both, spores of D. paleacea (Pteridophyta) and turi ons of S. polyrhiza (Angiospermae).