photoperiodismguralnl/gural/330photoperiodism.pdfdual day length plants • long- short day plants:...
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![Page 1: Photoperiodismguralnl/gural/330Photoperiodism.pdfDual Day length plants • Long- Short day plants: long days followed by short days • Kalanchoe • Short – Long day plants: sequence](https://reader033.vdocuments.site/reader033/viewer/2022060906/60a0e4a165b1a409ce6b4f9f/html5/thumbnails/1.jpg)
Photoperiodism• History• Photoperiodism and
flowering• Flowering response• Flower initiation• Biological clock
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History
• Demonstrated in 1920, Maryland mammoth tobacco mutant for flowering
• Daylength cause
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Daylength
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Photoperiodism and flowering
• Regulation of development by length of day
• Changes as you move from equator
• More predictable than climate: ie first frost
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Long day and Short day plants
• Long day plants• flower when
daylength exceeds a critical duration
• short day plants• flower when
daylength is less than a critical duration
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Dual Day length plants• Long- Short day plants: long days followed by short
days• Kalanchoe
• Short – Long day plants: sequence of short days followed by long days
• Trifolium (white clover)
• Day neutral plants:• no seasonality • depends on developmental status of plant
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Patterns
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Flowering response
• # of induction cycles • critical daylength vs
critical night length • light interruption
experiment • red light/far red light • photoreverisible• phytochrome
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Phytochrome response
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Variations • ripeness to respond • from cotyledon stage to
30 or 40 years of age • qualitative vs quantitative:
absolute or just longer or shorter days
• # of inductive cycles to flower: one to many
• mixed photoperiods: long to short, short to long
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Vernalization
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Flowering locus gene
40 days cold no cold FLC mutation, no cold
FLC mRNA
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Flower initiation
• perception • leaf data • grafting experiments • substance: "florigen", • role of gibberellins in
LD plants • floral meristem
changes
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Perception
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Treatment
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Floral Stimulus
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Steps to flowering
• Phytochrome• Blue light receptor
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Grafting experiments
• Transmissible substance• Source sink movement• Possible in phloem?• Substance?
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Four Pathways
0 h 18 h 42 h 5 d
Shift from SD --- LDIncrease in expression of AGL20