Plant Carotenoids: Pigments for Photoprotection, Visual Attraction, and Human Health
Photoprotection in plants
-
Upload
andrew-slater -
Category
Documents
-
view
53 -
download
1
description
Transcript of Photoprotection in plants
![Page 1: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/1.jpg)
Photoprotection in plants
Plant Physiology
Biology UNI PP11
![Page 2: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/2.jpg)
Plant job description
light
H2O
CO2
sugar
O2
The good stuff? The good stuff?
![Page 3: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/3.jpg)
Balanced photosynthesis
Photo Synthesis
High energy compounds
Harvests light energy
Uses harvested energy
Real time
![Page 4: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/4.jpg)
Unbalanced photosynthesis
Photo Synthesis
High energy compounds
bright light produces lots of energy
low-capacity biochemical pathways
use it slowly
Real time
Potential for destruction.
![Page 5: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/5.jpg)
Photosynthetic electron flow
ADP+ Pi ATP
H+
H+
H+
3 H+
NADPH
PS II PS I
H2O split
H2O
O2
Water splitting complex
Cytochrome complex
Thylakoid membrane
Coupling factor
e-
e-
e-
e-
![Page 6: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/6.jpg)
Too much energy in
• Biochemistry can’t use it
• Electrons pile up, high [O2]
• Nasty compounds– O2
-, 1 O2* (singlet oxygen)
– H2O2, .OH
• Oxidize chlorophyll (bleach)
• Oxidize lipids
• Can kill cells
![Page 7: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/7.jpg)
Photoprotection
• Broadest sense• Avoidance of excess energy into leaf
– Plant & leaf angles– Reduce absorbtion
• Doing something harmless with the energy • Unavoidable damage
![Page 8: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/8.jpg)
Plant and leaf angles
• Most plants have characteristic angles
• Upright– Desert– High latitude trees– Crowded plants
• Prostrate– Cold– Icy winds
![Page 9: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/9.jpg)
Leaves that move
• Adjust light interception (+/-)
![Page 10: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/10.jpg)
Examples of avoidance
![Page 11: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/11.jpg)
Light meets leaf
Reflected
Absorbed
Transmitted
All of the light is reflected, absorbed or transmitted.
![Page 12: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/12.jpg)
Increasing reflection
• White top surface– Hair– Wax– Air layers
• White bottom surface– Reflect externally– Reflect internally
![Page 13: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/13.jpg)
Increase transmittance
• Move and turn chloroplasts
![Page 14: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/14.jpg)
Photosystem geometryLight harvesting complex
Reaction center
![Page 15: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/15.jpg)
Shade and sun plants
Sun plantShade plant
Genetic control (capacity) and developmental control.
May not be able to adjust later.
![Page 16: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/16.jpg)
Where the energy can go
• Phytochemistry (synthesis half)
• Dissipated– Fluorescence of chlorophyll (red)– Transferred to carotenoids or xanthophylls
• Yellow pigments– Most carotenoids (constituitive)– Xanthophylls (“cycle” or seasonal)
• Can go on to make harmful O2 species
![Page 17: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/17.jpg)
Chlorophyll fluorescence
![Page 18: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/18.jpg)
Carotenoids
• Grab excitation energy from chlorophyll• Turns down the “volume” on chl excitation• Beta-carotene
– Always found with chlorophyll– Split in half to make Vitamin A
• Lutein– Retinal protection
• Xanthophylls
![Page 19: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/19.jpg)
Xanthophylls
• 3 kinds– Violaxanthin (nonprotective)– Antheroxanthin (protective)– Zeaxanthin (protective)
• Interconvert– Photoprotective forms in high light– Violaxanthin in low light– Proportional, constantly adjusted – Cycles (shuttles) back & forth
![Page 20: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/20.jpg)
Out in nature
• Conifers in winter– High light, low chemistry– High levels of photoprotective forms
• Sun plants– Shuttle back and forth, day to night
• Shade plants– May make & keep for day after sunfleck
• Pool sizes vary
![Page 21: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/21.jpg)
Visualizing xanthophyll action
• Light curve• High light plant• Photo-limited part• Synthesis-limited
part• Saturation• Reduction at high
light• Time scale: minutes
Xanthophylls or damage?
![Page 22: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/22.jpg)
Failure to protect• PS II rxn center vulnerable
• O2 generated
• No other protection• D1 protein degraded in light
– Part of light harvesting complex (LHC)– Disassemble (LHC), trade proteins, reassemble– Always happening in light – More light, more degradation
• Can’t keep up? Capacity for photosynthesis drops
![Page 23: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/23.jpg)
Problem solving at every level
• Plant orientation
• Leaf orientation
• Leaf spectral characteristics
• Protective pigments– Constituitive– Induced
• Repair
• Sometimes it still fails
![Page 24: Photoprotection in plants](https://reader035.fdocuments.in/reader035/viewer/2022062408/56813623550346895d9d9a85/html5/thumbnails/24.jpg)
Too much of a good thing
light
H2O
CO2
sugar
O2