I. Photosynthesis
Algal Physiology
I. Photosynthesis in algae
II. Characteristics to distinguish algal
divisions
“PSU” : Photosynthetic
Unit = Antennae + rxn
center
Light reactions: solar energy
is harvested and transferred
into the chemical bonds of
ATP and NADPH
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Chloroplasts
Thylakoid – flattened vesicles or sacks; thylakoid membrane is
where the pigments are
Stroma - space between inner membrane and thylakoids
Granum (pl: grana) – stacks of thylakoids
Pyrenoid – holds enzyme ribulose bisphospate carboxylase
(Rubisco) used in Calvin cycle
Calvin Cycle: C fixation from
CO2 to sugar using energy
from ATP and NADPH
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Pigment Location
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What light can be used for photosynthesis?
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Pigments: Primary
What light can be used for photosynthesis?
PAR = photosynthetically active radiation = 400-700 nm
1. Chlorophylls – green pigments, embedded in thylakoid
membrane. Chl a is the main player: used in all algae and land
plants.
Chl a absorbs light primarily in
the blue and far-red regions
Reflects green  why most
plants appear green
Must also deal with UV light (280-320 nm); damage DNA, proteins
- B-carotene, aromatic amino acids absorb UVB
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What’s wrong with this picture?
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What’s wrong with this picture?
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Algae have accessory pigments: Allow harvesting of light
Algae have accessory pigments: Allow harvesting of light
at “middle” wavelengths, then channel energy to Chl a
at “middle” wavelengths, then channel energy to Chl a
“PSU” : Photosynthetic
Unit = Antennae + rxn
center
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How we measure photosynthetic rates (primary
productivity):
Algal accessory pigments:
• Measure Oxygen release
• With electrodes using O2meter or Chemical titration
• Use Light and Dark Bottles
• Dark Bottles measure Respiration
• Light Bottles measure Ps - Rs = Net photosynthesis
• Light Bottle O2 + Dark Bottle O2 = Gross photosynthesis
2. Carotenoids – brown, yellow, or red pigments.
Hydrocarbons with or without an oxygen molecule
= carotenes and xanthophylls.
3. Phycobilins – red or blue pigments. Water soluble.
Located on the surface of thylakoids in red algae,
associated with proteins to form phycobilisomes
• Photosynthetic Rate measured as O2 /g/hr
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How we study photosynthesis: The P-E curve
P= photosynthesis= oxygen evolved or carbon fixed
E= irradiance= measure of the amount of energy falling
on a flat surface
P-E curve= useful to compare the physiology of light
harvesting pigments
Photosynthetic Rate
O2 /g/hr
O2 /g/hr
Photosynthetic Rate
P
How we study photosynthesis:
P-E curve formally known as the Ps/I curve
Light Intensity
Light Intensity
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1.
How we study photosynthesis: The P-E curve
2.
O2 /g/hr
+
0
-
1.
Light Intensity
Ec = Compensation point: When photosynthesis equals respiration
1.
2.
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Photosynthetic Rate
O2 /g/hr
Photosynthetic Rate
How we study photosynthesis: The P-E curve
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2.
+
0
-
1.
2.
Light Intensity
Ic = Compensation point: When photosynthesis equals respiration
Pmax = Maximum production
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1.
2.
3.
How we study photosynthesis: The P-E curve
2.
2.
3.
O2 /g/hr
+
0
-
1.
Photosynthetic Rate
O2 /g/hr
Photosynthetic Rate
How we study photosynthesis: The P-E curve
Light Intensity
Ic = Compensation point: When photosynthesis equals respiration
Pmax = Maximum production
Photoinhibition = Damage to photosystems due to high irradiance
1.
2.
3.
4.
2.
2.
3.
4.
+
0
-
1.
Light Intensity
Ic = Compensation point: When photosynthesis equals respiration
Pmax = Maximum production
Photoinhibition = Damage to photosystems due to high irradianc
Initial slope (alpha) = Indicative of photosynthetic efficiency
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1.
2.
3.
4.
5.
How we study photosynthesis: The P-E curve
2.
2.
3.
4.
+
0
-
1.
O2 /g/hr
5.
Light Intensity
Ic = Compensation point: When photosynthesis equals respiration
Pmax = Maximum production
Photoinhibition = Damage to photosystems due to high irradianc
Initial slope (alpha) = Indicative of photosynthetic efficiency
Ek= Saturating irradiance
1.
2.
3.
4.
5.
6.
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Photosynthetic Rate
O2 /g/hr
Photosynthetic Rate
How we study photosynthesis: The P-E curve
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2.
2.
3.
4.
+
0
-
1.
6.
5.
Light Intensity
Ic = Compensation point: When photosynthesis equals respiration
Pmax = Maximum production
Photoinhibition = Damage to photosystems due to high irradianc
Initial slope (alpha) = Indicative of photosynthetic efficiency
Ik= Saturating irradiance
Gross photosynthesis = Total production
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1.
2.
3.
4.
5.
6.
7.
How we study photosynthesis: The P-E curve
2.
2.
3.
4.
+
0
-
1.
6.
O2 /g/hr
7.
Light Intensity
Ic = Compensation point: When photosynthesis equals respiration
Pmax = Maximum production
Photoinhibition = Damage to photosystems due to high irradianc
Initial slope (alpha) = Indicative of photosynthetic efficiency
Ik= Saturating irradiance
Gross photosynthesis = Total production
Net photosynthesis = Gross production – Respiration
1.
2.
3.
4.
5.
6.
7.
Photosynthetic Rate
O2 /g/hr
Photosynthetic Rate
How we study photosynthesis: The P-E curve
2.
2.
3.
4.
+
0
-
1.
6.
5.
7.
Light Intensity
Ec = Compensation point: When photosynthesis equals respiration
Pmax = Maximum production
Photoinhibition = Damage to photosystems due to high irradiance
Initial slope (alpha) = Indicative of photosynthetic efficiency
Ek= Saturating irradiance
Gross photosynthesis = Total production
Net photosynthesis = Gross production – Respiration
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How we measure photosynthetic rates (primary
productivity):
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II. Algal characteristics for distinguishing divisions:
• Important Considerations:
• Temperature
• Saturating Light?
• Background gasses – run blanks
• Ambient primary productivity by phytoplankton when using
seawater
• Nutrients
1. Pigments
2. Storage products
3 C
3.
Cellular/plastid
llul r/pl stid structure
structur
• Other methods
• CO2 measurement (by pH)
• C14 isotope tracers
• Infrared gas analysis
4. Motility (e.g. +/- flagella)
5. Life history
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Pigments
Algal pigments:
Chlorophyta:
- Chl:
- Carotenoids:
1. Chlorophylls – green pigments, embedded in
thylakoid membrane. Chl a is the main player:
used in all algae and land plants.
- Phycobilins:
2. Carotenoids – brown, yellow, or red pigments.
Ochrophyta:
- Chl:
- Carotenoids:
- Phycobilins:
Hydrocarbons
y
with or without an oxygen
yg molecule
= carotenes and xanthophylls.
3. Phycobilins – red or blue pigments. Water soluble.
Located on the surface of thylakoids in red algae,
associated with proteins to form phycobilisomes
Rhodophyta:
- Chl:
- Carotenoids:
- Phycobilins:
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2 forms:
II. Algal characteristics for distinguishing divisions:
Storage products
alpha 1,4 linked = starches (Chlorophyta, Rhodophyta)
1. Pigments
2. Storage products
(e.g. floridean,
amylopectin, amylose
starches)
3. Cellular/plastid structure
beta 1,3 linked = sugars (Ochrophyta)
4. Motility (e.g. +/- flagella)
5. Life history
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(e.g. laminarin,
chrysolaminarin,
mannitol)
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Storage Products:
II. Algal characteristics for distinguishing divisions:
Chlorophyta:
Starches:
1. Pigments
2. Storage products
Ochrophyta:
Sugars:
3. Chloroplast structure
4. Motility (e.g. +/- flagella)
Rhodophyta:
Starches:
5. Life history
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Chloroplast structure
Chlorophyta:
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Chloroplast Structure:
Ochrophyta:
Chlorophyta:
Membranes:
Thylakoids:
Ochrophyta:
Membranes:
Rhodophyta:
Thylakoids:
Rhodophyta:
Membranes:
Thylakoids:
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To have or not to have…………….
II. Algal characteristics for distinguishing divisions:
Chlorophyta:
Ochrophyta:
1. Pigments
2. Storage products
3 C
3.
Cellular/plastid
llul r/pl stid structure
structur
Rhodophyta:
4. Motility (e.g. +/- flagella)
5. Life history
…….flagella
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Flagella:
II. Algal characteristics for distinguishing divisions:
Chlorophyta:
1. Pigments
2. Storage products
Ochrophyta:
3 C
3.
Cellular/plastid
llul r/pl stid structure
structur
4. Motility (e.g. +/- flagella)
5. Life history
Rhodophyta:
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Algal life histories : Terminology to know and love
Algal life histories vary
Spore (mitospore, meiospore):
Fertilization
Gamete:
Sporophyte:
Mitosis
Gametophyte:
Vegetative
Reproduction
Haplontic:
Meiosis
Diplontic:
Alternation of Generations:
Heteromorphic:
Diplohaplontic
Haplodiplontic
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Algal Life Cycles
Isomorphic:
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Algal Life Cycles
Three main patterns:
Three main patterns:
1) Haplontic
2) Diplontic
3) Alternation of Generations
• Isomorphic
• Heteromorphic
1) Haplontic
2) Diplontic
3) Alternation of Generations
• Isomorphic
• Heteromorphic
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“animal-like” life history
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Algal Life Cycles
Algal Life Cycles
Three main patterns:
Three main patterns:
1) Haplontic
2) Diplontic
3) Alternation of Generations
• Isomorphic
• Heteromorphic
1) Haplontic
2) Diplontic
3) Alternation of Generations
• Isomorphic
• Heteromorphic
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Algal Life Cycles
“haplodiplontic”
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Life cycles:
Three main patterns:
Chlorophyta:
1) Haplontic
2) Diplontic
3) Alternation of Generations
• Isomorphic
• Heteromorphic
Ochrophyta:
Rhodophyta:
“diplohaplontic”
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Example: Fucus
Example: Ulva
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Example: Nereocystis
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