Light-induced fern-spore germination: Effect of spore age on responsivity to light

Developmental Physiology Apparent Dark Decay of Phytochrome Pfr in Fern Spores

“…The light sources are given in Haupt and Filler (1986), the interference filters with their characteristics in Haupt et al (1988). All irradiations were 2 min with 11 to 18 Wm-2 ; by means of suitable experiments, it was confirmed that these irradiations were saturating.…”

“…Spores of Dryopteris filix-mas and D. paleacea were harvested in South Sweden, summer 1983, and in the Botanical Garden at Erlangen, summer 1984, respectively, and stored at 6°C until used for the experiments (winter 1985/86). They were sown on 0.70/0 agar with mineral salts as reported earlier (Haupt, 1985;Haupt et al, 1988) and kept in darkness, except for the experimental irradiations, which were preceded and followed by short exposures to dim green safelight during the necessary manipulations (1.3 mWm-2 ; cf. also Haupt, 1985).…”

“…All irradiations were 2 min with 11 to 18 Wm-2 ; by means of suitable experiments, it was confirmed that these irradiations were saturating. The <jJ values (Prr/Plot in photoequilibrium) thus obtained with these filters were 0.86; 0.73; 0.54; 0.26, respectively, based on measurements with 124 kDa Avena phytochrome (Haupt et al, 1988). The percentage of germination was counted 7 and 6 days after sowing for D.filix-mas and D. paleacea, respectively.…”

“…Indeed, for fern-spore germination, Haupt et al (1988) have shown that PCr> established by red irradiation as early as 30 min after sowing, undergoes an apparent PCr decay, the time constants of which depend on the spore age after harvesting. Moreover, the inducing effect of a given pulse of red light is the lower, the faster the PCr decay has been found.…”

“…In the present paper it will be asked how this apparent PCr decay depends on the temperature. To date, it could not be decided yet whether the apparent PCr decay is based on dark reversion (P C r Prj, with the total phytochrome (P tot) remaining constant, or on dark destruction, with no compensation for the loss of Pcr-If the former is assumed, the half-life is in the range of 15 to 40 hours, but for the latter, 4 to 15 hours have been estimated (Haupt et al, 1988). In order to decide between these possible interpretations, it might be helpful to analyse additional factors that affect the apparent PCr decay.…”