Transcript Photosynthesis or “You light up my life”

Light & Photosynthesis
or
“You light up my life”
A/H 100G
J.G. Mexal
CO2 capture
Basic Photosynthetic Reaction
• CO2 + H2O
• 1.47 lb 0.60 lb
λ
CH2O + O2
1.00 lb
1.07 lb
Photosynthesis
Action Spectra of Lights vs Chl a & b Absorption
Cool white
fluorescent light
Incandescent light
Chlorophyll A & B
Photosynthesis
Light Compensation and Saturation Points
Net Ps (mgCO2/cm2/h)
S.P.
C.P.
2000
4000
6000
Light Intensity (fc)
Photosynthesis
Sun vs Shade Leaves
Sun
Shade
Epidermis
Palisade
Mesophyll
Spongy
Mesophyll
Epidermis
Stomata
Photosynthesis
Pathways for Photosynthesis
• C-3
• C-4
• CAM
= most crops
= arid shrubs, grasses, pineapple
= succulents
– (crassulacean acid metabolism)
Photosynthesis
C3, C4, and CAM Plants
C3 Plants
C4 Plants
CAM Plants
Spinach
Corn
Agave
Beans
Bermuda grass Jade plant
Bentgrass
Russian thistle Pineapple
Mulberry
4-wing
saltbush
Pigweed
Chile
Sansevieria
Cacti
Photosynthesis
Characteristics of C3 and C4 Plants
Characteristic
C3 Plants
C4 Plants
Tissue w/ chloroplasts
Mesophyll
Transpiration
High
Mesophyll &
bundle sheaths
Low
Optimum T
15-25C
30-40C
Light intensity (saturation) 3,000 fc
6,000+ fc
Photorespiration
Measurable
Not measurable
Compensation point
30-70 ppm CO2 0-10 ppmCO2
Ps pathways
1
2
Ps @ hi T & hi light
Low
High
Photosynthesis
Simplified C3 Pathway
Photosynthesis
C3 Leaf Structure
Epidermis
Palisade mesophyll
Vein
Vein
Spongy mesophyll
Photosynthesis
Light Compensation and Saturation Points
Photosynthesis
Interaction between CO2 and Light Intensity
Photosynthesis Rate
1,300 ppm CO2
1600 ppm CO2
360 ppm CO2
Light Intensity
Photosynthesis
Simplified C4 Pathway
Spatial Separation
Photosynthesis
Simplified C4 Pathway
Photosynthesis
C4 Leaf Structure
Bundle sheath
cells
Vein
Mesophyll
Photosynthesis
Distribution of C4 Plants/ Oecologia 23:1-12:1978
Percent of Grass Taxa
Percent of Dicot Taxa
Photosynthesis
C3 & C4 Response to Light Intensity
Photosynthesis
Sugarcane- C4
Clover- C3
Tobacco- C3
Philodendron-C3
Light Intensity
Photosynthesis
Simplified CAM Pathway
Temporal Separation
3-carbon
compound
Photosynthesis
Simplified CAM Pathway
Photosynthesis
What is this?????
Things to Know
• What happens to all the
light striking the earth’s
surface
• Light attributes
– Quality
– Quantity
– Duration
• Plant pigments
– Imp. Wavelengths
– Actions
• Photoperiod response
–
–
–
–
Long-day
Short-day
Day-neutral
Important dates (why?)
• Ps Reaction
– Basic
– C3, C4, CAM
Quiz Questions
• Give the basic photosynthesis reaction and where does it
take place?
• Describe the characteristics of C-3 and C-4 plants. Give
examples of a C-3 and C-4 plant.
• Describe the differences between a C-4 and CAM plant.
Give an example of a CAM plant.
• What is a ‘short-day plant’? ‘long-day plant’? ‘day-neutral
plant’?
• How do plant ‘tell time’? What’s the reaction?
• Why do C-4 plants have a higher rate of photosynthesis.
Describe leaf morphology of both.
Light and Photobiology
Electromagnetic Spectrum
Energy (kcal/cm
80
60
40
-0.9376
y = 19176x
R2 = 0.99
20
0
300
400
500
600
Wavelength (nm)
700
800
900
Photosynthesis
Leaf Tissues & Function
• Tissue
– Epidermis
– Guard cells & stomates
– Chlorophyllcontaining cells
– Veins
• Primary Functions
– Protective cells (keep
water within leaf)
– Allow CO2 & O2
diffusion for Ps & Rs
– Manufacture ATP &
glucose
– Translocate H2O and
nutrient to, and CHO
& AA away from, the
leaves