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Action spectrum of photosynthesis Fig 39.3 Fig 39.12 Seedling germination may depend on light Fig 39.15 Phytochrome: a reversible receptor http://www.mcdb.ucla.edu/Research/Tobin/research.html Hey, want to swap some pollen? I don’t have any flowers. I guess I will have to find another plant. I hate when that happens. You give really good pollen. Plants use day length to synchronize flowering Fig 39.13 The critical period is actually night length Fig 39.13 Phytochrome regulates flowering time Fig 39.14 Plants use night length to determine the season. What about daily time... the circadian clock Circadian Rhythms: daily patterns set by light (northern flying squirrel) Phytochrome sets the circadian clock http://www.mcdb.ucla.edu/Research/Tobin/research.html http://plantsinmotion.bio.indiana.edu/plantmotion/movements/leafmovements/clocks.html (oxalis) http://plantsinmotion.bio.indiana.edu/plantmotion/movements/tropism/tropisms.html (sunflower tracking) The molecular identity of the circadian clock is unknown http://www.ou.edu/wanglab/Circadian.html CCA1 is a transcription factor that regulates some photosynthetic genes. 25 28 31 34 37 40 43 46 49 52 55 57 http://www.mcdb.ucla.edu/Research/Tobin/research.html Overexpression of CCA1 in transgenic Arabidopsis plants abolished the circadian rhythms of several genes with dramatically different phases. http://www.mcdb.ucla.edu /Research/Tobin/research. html Plants were created that lack a functional CCA1 gene http://www.mcdb.u cla.edu/Research/T obin/research.html With no CCA1 protein, phytochrome induction of Lhcb RNA is reduced to 60% of the normal level. http://www.mcdb.ucl a.edu/Research/Tobin /research.html http://www.mcdb.ucla.edu/Research/Tobin/research.html http://www.mcdb.ucla.edu/Research/Tobin/research.html Plants overexpressing CCA1 had delayed flowering. Furthermore, leaf movement rhythms were abolished CCA1 is part of the oscillator, but it is not THE oscillator/clock. http://www.ou.edu/wanglab/Circadian.html Enjoy your break...