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 study photosynthesis: The Ps/I curve
Algal accessory pigments:
1.
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
1.
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Pmax = Maximum production
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How we study photosynthesis: The Ps/I curve
How we study photosynthesis: The Ps/I curve
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Pmax = Maximum production
Ik = Saturating irradiance (where initial slope meets Pmax)
1. Pmax = Maximum production
2. Ik = Saturating irradiance
3. Gross photosynthesis = Total production
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How we study photosynthesis: The Ps/I curve
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How we study photosynthesis: The Ps/I curve
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3.
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5.
1. Pmax = Maximum production
2. Ik = Saturating irradiance
3. Gross photosynthesis = Total production
4. Net photosynthesis = Gross production – Respiration
4.
2.
1. Pmax = Maximum production
2. Ik = Saturating irradiance
3. Gross photosynthesis = Total production
4. Net photosynthesis = Gross production – Respiration
5. Ic = Compensation point: When photosynthesis equals respiration
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How we study photosynthesis: The Ps/I curve
How we study photosynthesis: The Ps/I curve
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1.
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1. Pmax = Maximum production
2. Ik = Saturating irradiance
3. Gross photosynthesis = Total production
4. Net photosynthesis = Gross production – Respiration
5. Ic = Compensation point: When photosynthesis equals respiration
6. Initial slope (alpha) = Indicative of photosynthetic efficiency
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Pmax = Maximum production
Ik = Saturating irradiance
Gross photosynthesis = Total production
Net photosynthesis = Gross production – Respiration
Ic = Compensation point: When photosynthesis equals respiration
Initial slope (alpha) = Indicative of photosynthetic efficiency
Photoinhibition = Damage to photosystems due to high irradiance
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How we study photosynthesis: The Ps/I curve
How we measure photosynthetic rates (primary
productivity):
1.
• Measure Oxygen release (Biological Oxygen Demand –
BOD):
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• With electrodes using O2 = O2 meter 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
4.
• Photosynthetic Rate measured as O2 /g/hr
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2.
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How we measure photosynthetic rates (primary
productivity):
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. Cellular/plastid structure
• 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.
Heterokontophyta:
- Chl:
- Carotenoids:
- Phycobilins:
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
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 (Heterokontophyta)
4. Motility (e.g. +/- flagella)
5. Life history
(e.g. laminarin,
chrysolaminarin,
mannitol)
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Storage Products:
II. Algal characteristics for distinguishing divisions:
Chlorophyta:
Starches:
1. Pigments
2. Storage products
Heterokontophyta:
Sugars:
3. Chloroplast structure
4. Motility (e.g. +/- flagella)
Rhodophyta:
Starches:
5. Life history
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Chloroplast structure
Chlorophyta:
Chloroplast Structure:
Heterokontophyta:
Chlorophyta:
Membranes:
Thylakoids:
Heterokontophyta:
Membranes:
Rhodophyta:
Thylakoids:
Rhodophyta:
Membranes:
Thylakoids:
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To have or not to have…………….
II. Algal characteristics for distinguishing divisions:
Chlorophyta:
Heterokontophyta:
1. Pigments
2. Storage products
3. Cellular/plastid structure
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
Heterokontophyta:
3. Cellular/plastid structure
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:
Diplontic:
Meiosis
Alternation of Generations:
Heteromorphic:
Diplohaplontic
Haplodiplontic
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Isomorphic:
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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
“animal-like” life history
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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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“haplodiplontic”
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Algal Life Cycles
Life cycles:
Three main patterns:
Chlorophyta:
1) Haplontic
2) Diplontic
3) Alternation of Generations
• Isomorphic
• Heteromorphic
Heterokontophyta:
Rhodophyta:
“diplohaplontic”
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Example: Fucus
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Example: Ulva
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Example: Nereocystis
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