Temporal separation of two components of phytochrome action |
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Authors: | G C WHITELAM C B JOHNSON |
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Institution: | Department of Botany, Plant Science Laboratories, University of Reading, Whiteknights, Reading, RG6 2AS, Berkshire, U.K. |
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Abstract: | Abstract In germinating seedlings of Sinapis alba nitrate reductase activity as assayed in vivo becomes accessible to phytochrome control between 15 and 17 h after sowing. Phytochrome operates via the high irradiance reaction to control nitrate reductase activity in the period 15 to 20 h after sowing. Both continuous red light and far-red light elicit this response with a strong fluence rate dependency being apparent in each case. The induction of nitrate reductase activity by light pulses at 20 h after sowing is greatly influenced by red light pre-treatments (operating through phytochrome) given between 0 and 15 h after sowing. Low fluence rate pre-treatments reduce the effectiveness of a subsequent pulse to below the level of a dark control whilst high fluence rate pre-treatments greatly increase the effectiveness of a subsequent pulse. |
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Keywords: | Sinapis alba Cruciferae white mustard phytochrome photomorphgenesis nitrate reductase |
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