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PHYTOCHROME

PHYTOCHROME. Pr. Pfr. Pr. Pfr. Pr. Real spectra!. The Score So Far:. Light is a hormone. s. s. Phytochrome is a photoreceptor. Photoswitchable between Red and Far red absorbing forms. s. s. Complex absoprtion spectra. The Bunsen Roscoe Reciprocity Law.

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PHYTOCHROME

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  1. PHYTOCHROME

  2. Pr Pfr Pr Pfr Pr

  3. Real spectra!

  4. The Score So Far: Light is a hormone s s Phytochrome is a photoreceptor Photoswitchable between Red and Far red absorbing forms s s Complex absoprtion spectra

  5. The Bunsen Roscoe Reciprocity Law Fluence rate x time = Response magnitude

  6. The Bunsen Roscoe Reciprocity Law Fluence rate x time = Response magnitude (µmol m-2 s-1) x s = µmol m-2

  7. 1st internode length, mm

  8. [Pfr] 1st internode length, mm

  9. 1/10 firefly flash

  10. RED hn Pr Pfr FAR RED hn

  11. What happens after a ligand binds to a recepor?

  12. Membrane Cell Pr Cytoplasm Nucleus

  13. Where might phytochrome be? ? Pr ? Nucleus

  14. Phytochrome Holoprotein = Apoprotein + Chromophore Phytochromobilin

  15. “Two-Component” regulation Phospho-transfer Origin of plant phytochrome

  16. Actually, there is more than one receptor PHYA PHYBPHYCPHYDPHYE ...

  17. GENETICS To the rescue... White light The hy phenotype wt, mutant, mutant

  18. GENETICS To the rescue... White light The hy phenotype phya = phya phya found with a far-red light screen, not with white-light screen: WHY??? hy3 = phyb wt, mutant, mutant

  19. WHITE LIGHT GROWN Wild type phyAphyBphyBDEphyABEphyABDE http://www.photobiology.info/Franklin-PM.html

  20. Etiolated seedlings Lots of phytochrome Light labile Light-grown seedlings Scant phytochrome Light stable (plants) “TYPE II” “TYPE I”

  21. Etiolated, FR Light, R

  22. Leaves are green

  23. PHYTOCHROME PART III

  24. 730 nm 660 nm

  25. RED hn Pr Pfr FAR RED hn

  26. Estimated Phytochrome Photoequilibrium Pfr/Ptotal R:FR ratio After Figure 2 of Smith 1982. Ann Rev Plant Physiol 33: 481-518.

  27. Pr Daylight spectrum R:FR 1.05-1.25 Pfr

  28. Pr Canopy spectrum (green) R:FR < 1 Pfr

  29. Estimated Phytochrome Photoequilibrium Pfr/Ptotal R:FR ratio After Figure 2 of Smith 1982. Ann Rev Plant Physiol 33: 481-518.

  30. Above leaf Below Leaf

  31. Shade avoidance response Sun Shade Sun Shade

  32. Shade ... ... Sun

  33. Life in a crowd

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