Phytochrome and flowering . When is the right time to flower?
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Phytochrome and flowering. When is the right time to flower? • Unreliable indicators of time of year – Temperature – Moisture – Light levels • Reliable: length of day/night – Varies with season – Varies with latitude • Detected by phytochrome
description
Phytochrome and flowering . When is the right time to flower?. Unreliable indicators of time of year Temperature Moisture Light levels Reliable: length of day/night Varies with season Varies with latitude Detected by phytochrome. Sunlight. Mostly red A little far red. P r. P r. - PowerPoint PPT Presentation
Transcript of Phytochrome and flowering . When is the right time to flower?
Phytochrome and flowering.When is the right time to flower?
• Unreliable indicators of time of year– Temperature – Moisture – Light levels
• Reliable: length of day/night – Varies with season– Varies with latitude
• Detected by phytochrome
Sunlight
Mostly red
A little far red
Pr
Pfr
In sunlight
Pfr
PrPr
Pr
Pr
Pr
Pr
Pr
Pr
Pr
Pfr
Pfr
Pfr
Pfr
Pfr
PfrPfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pr
Pfr
Pfr
In sunlight most P gets converted to Pfr form.
Pr
Pfr
Start of night
Pfr
PrPr
Pr
Pr
Pr
Pr
Pr
Pr
Pr
Pfr
Pfr
Pfr
Pfr
Pfr
PfrPfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pr
Pfr
Pfr
Most P in Pfr form.
Pfr
In the dark
Pfr
PrPr
Pr
Pr
Pr
Pr
Pr
Pr
Pr
Pfr
Pfr
Pfr
Pfr
Pfr
PfrPfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
PfrPr
Pfr
Pfr
Pfr form changes gradually to Pr form.
Pr
Pr
Pr
Pr
Pfr
After a short night
Pfr
PrPr
Pr
Pr
Pr
Pr
Pr
Pr
Pr
Pfr
Pfr
Pfr
Pfr
Pfr
PfrPfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
PfrPr
Pfr
Pfr
much Pfr still remains.
Pr
Pr
Pr
Pr
Pfr
Later in the night
Pfr
PrPr
Pr
Pr
Pr
Pr
Pr
Pr
Pr
Pfr
Pfr
PfrPfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pr
Pfr
Pfr
more Pfr changes to Pr.
Pr
Pr
Pr
Pr
Pfr
After a long night
Pfr
PrPr
Pr
Pr
Pr
Pr
Pr
Pr
Pr
Pfr
Pfr
Pfr
Pfr
Pfr
PfrPfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
PfrPr
Pfr
Pfr
all the Pfr is gone.
Pr
Pr
Pr
Pr
Pr
Pr
Pr
Pr
Pr
Pr
PrPr
Pr
PrPr
Pr
Pr
Pr
Pfr
Next day
Pfr
PrPr
Pr
Pr
Pr
Pr
Pr
Pr
Pr
Pfr
Pfr
Pfr
Pfr
Pfr
PfrPfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pfr
Pr
Pfr
Pfr
Most P gets converted to Pfr form again.
Long day plant = Short night plants
• Needs short night to flower• Needs Pfr still present at end of night• Pfr promotes flowering for LDPs
Short day plant = Long night plant
• Needs long night to flower• Needs Pfr gone at end of night• Pfr inhibits flowering for SDPs
Can trick a SDP into not flowering with a brief flash of red light during the long night, this resets much of its phytochrome to Pfr form.
LDP SDP
Long day: Pfr remains at end of short night.
Pfr promotes flowering for LDPs.
Pfr inhibits flowering for SDPs.
Short day: Pfr gone at end of long night.
Lack of Pfr promotes flowering for LDPs.
Lack of Pfr inhibits flowering for SDPs.
Blue light responses, chapter 18
1. Phototropism
2. Stomatal opening
3. Chlorophyll and carotenoid synthesis
4. Inhibition of hypocotyl elongation
5. Altered gene expression
Phototropism - directional growthtoward light.
Most evident indark-grown seedlings.
Characteristic blue-light action spectrum Fig. 18.1
“”three finger” pattern
Figure 18.2
How does bending toward light happen?
Mechanically, what’s going on?
1. Collapse of cells on near side
2. Increased growth on far side, no change on near side.
3. Reduced growth on near side, no change on far side.
Wild type
Mutant
Blue light response causes differentialgrowth by slowingcell expansion on near side.
Blue light responseis very rapid.
Fig. 18.6 Blue light depolarizesthe plasmamembranebefore reducinggrowth rate
Blue light andstomatal opening
The blue lighteffect is not due to increasedphotosynthesis
Fig. 18.11. Action spectrum for blue lightstimulated stomatal opening in red light background.
Blue light stimulates guard cell H+ pumps.
Blue light stimulates a proton pump on guard cell plasmamembrane
Blue light regulates osmotic relations of guard cells:1. H+, K+, Cl- fluxes at plasmamembrane2. Malate synthesis increases3. Sucrose synthesis increases4. K+, Cl-, malate, and sucrose accumulate in vacuole
