The effect of red and far-red light in the high irradiance reaction of phytochrome (hypocotyl growth in dark-grown Sinapis alba L.) |
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Authors: | BRIGITTE HEIM EBERHARD SCHÄFER |
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Institution: | Biologisches Institut der Universität, Schänzlestrasse I, D-7800 Freiburg, Federal Republic of Germany |
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Abstract: | Abstract. Fluence-rate response curves were determined for the inhibition of hypocotyl growth in 54-h-old dark-grown Sinapis alba L. seedlings by continuous or hourly 5 min far-red light irradiation (24 h). Just as in red light ( Heim & Schäfer, 1982 ), a fluence-rate dependence was observed for both kinds of irradiations, even if only 35% of the continuous light effect could be substituted for by hourly far-red pulses. The same total fluence was used for the two different light regimes. Measurements of Pfr and Pfr/Ptot showed a strong fluence-rate dependence under continuous light which only partially paralleled the fluence-rate response curves for the inhibition of the hypocotyl growth. It was concluded that neither spectrophotometrically determined levels of Pfr nor Pfr/Ptot can be the only light-dependent factor controlling hypocotyl lengthening under continuous irradiation. |
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Keywords: | Sinapis alba L Brassicaceae white mustard high irradiance response hypocotyl growth photoequilibrium (-stationary state) photomorphogenesis phytochrome |
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