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1
Algal Physiology
I. Photosynthesis in algaeII. Characteristics to distinguish algal
divisions
1
I. Photosynthesis
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3
Light reactions: solar energy is harvested and transferred into the chemical bonds of ATP and NADPH
“PSU” : Photosynthetic Unit = Antennae + rxn center
4
2
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Calvin Cycle: C fixation from CO2 to sugar using energy from ATP and NADPH
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
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Pigment Location
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What light can be used for photosynthesis?
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3
What light can be used for photosynthesis?PAR = photosynthetically active radiation = 400-700 nm
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Must also deal with UV light (280-320 nm); damage DNA, proteins- B-carotene, aromatic amino acids absorb UVB
Pigments: Primary
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
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Chl a absorbs light primarily in the blue and far-red regions
Reflects green why most plants appear green
What’s wrong with this picture?
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What’s wrong with this picture?
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4
Algae have accessory pigments: Allow harvesting of light at “middle” wavelengths, then channel energy to Chl a
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Algae have accessory pigments: Allow harvesting of light at “middle” wavelengths, then channel energy to Chl a
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“PSU” : Photosynthetic Unit = Antennae + rxn center
2. Carotenoids – brown, yellow, or red pigments. Hydrocarbons with or without an oxygen molecule = carotenes and xanthophylls.
Algal accessory pigments:
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3. Phycobilins – red or blue pigments. Water soluble. Located on the surface of thylakoids in red algae, associated with proteins to form phycobilisomes
How we measure photosynthetic rates (primary productivity):
• 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 O + Dark Bottle O = Gross photosynthesis
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• Light Bottle O2 + Dark Bottle O2 = Gross photosynthesis
• Photosynthetic Rate measured as O2 /g/hr
5
How we study photosynthesis: P-E curve formally known as the Ps/I curve
P= photosynthesis= oxygen evolved or carbon fixedE= irradiance= measure of the amount of energy falling
on a flat surfaceP-E curve= useful to compare the physiology of light
harvesting pigments
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O2 /g/hr
Light Intensity
Ph
oto
syn
the
tic R
ate
How we study photosynthesis: The P-E curve
O2 /g/hr
Ph
oto
syn
the
tic R
ate
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Light Intensity
P
How we study photosynthesis: The P-E curve
2.
O2 /g/hr
ho
tosy
nth
etic
Ra
te
+0
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1. Ec = Compensation point: When photosynthesis equals respiration
1. Light Intensity
P 0-
How we study photosynthesis: The P-E curve
2.
O2 /g/hr
ho
tosy
nth
etic
Ra
te
+0
2.
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1. Ic = Compensation point: When photosynthesis equals respiration2. Pmax = Maximum production
1. Light Intensity
P 0-
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How we study photosynthesis: The P-E curve
2.
O2 /g/hr
ho
tosy
nth
etic
Ra
te
+0
2.
3.
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1. Ic = Compensation point: When photosynthesis equals respiration2. Pmax = Maximum production3. Photoinhibition = Damage to photosystems due to high irradiance
1. Light Intensity
P 0-
How we study photosynthesis: The P-E curve
2.
O2 /g/hr
ho
tosy
nth
etic
Ra
te
+0
2.
3.4.
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1. Ic = Compensation point: When photosynthesis equals respiration2. Pmax = Maximum production3. Photoinhibition = Damage to photosystems due to high irradianc4. Initial slope (alpha) = Indicative of photosynthetic efficiency
1. Light Intensity
P 0-
How we study photosynthesis: The P-E curve
2.
O2 /g/hr
ho
tosy
nth
etic
Ra
te
+0
2.
3.4.
23
1. Ic = Compensation point: When photosynthesis equals respiration2. Pmax = Maximum production3. Photoinhibition = Damage to photosystems due to high irradianc4. Initial slope (alpha) = Indicative of photosynthetic efficiency5. Ek= Saturating irradiance
1. Light Intensity
P 0-
5.
How we study photosynthesis: The P-E curve
2.
O2 /g/hr
ho
tosy
nth
etic
Ra
te
+0
2.
3.4. 6.
24
1. Ic = Compensation point: When photosynthesis equals respiration2. Pmax = Maximum production3. Photoinhibition = Damage to photosystems due to high irradianc4. Initial slope (alpha) = Indicative of photosynthetic efficiency5. Ik= Saturating irradiance6. Gross photosynthesis = Total production
1. Light Intensity
P 0-
5.
7
How we study photosynthesis: The P-E curve
2.
O2 /g/hr
ho
tosy
nth
etic
Ra
te
+0
2.
3.4. 6. 7.
25
1. Ic = Compensation point: When photosynthesis equals respiration2. Pmax = Maximum production3. Photoinhibition = Damage to photosystems due to high irradianc4. Initial slope (alpha) = Indicative of photosynthetic efficiency5. Ik= Saturating irradiance6. Gross photosynthesis = Total production7. Net photosynthesis = Gross production – Respiration
1. Light Intensity
P 0-
How we study photosynthesis: The P-E curve
2.
O2 /g/hr
ho
tosy
nth
etic
Ra
te
+0
2.
3.4. 6. 7.
26
1. Ec = Compensation point: When photosynthesis equals respiration2. Pmax = Maximum production3. Photoinhibition = Damage to photosystems due to high irradiance 4. Initial slope (alpha) = Indicative of photosynthetic efficiency5. Ek= Saturating irradiance6. Gross photosynthesis = Total production7. Net photosynthesis = Gross production – Respiration
1. Light Intensity
P 0-
5.
How we measure photosynthetic rates (primary productivity):
• Important Considerations:• Temperature• Saturating Light? • Background gasses – run blanks• Ambient primary productivity by phytoplankton when using seawater• Nutrients
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• Nutrients
• Other methods• CO2 measurement (by pH)• C14 isotope tracers• Infrared gas analysis
II. Algal characteristics for distinguishing divisions:
1. Pigments
2. Storage products
3 C llul r/pl stid structur
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3. Cellular/plastid structure
4. Motility (e.g. +/- flagella)
5. Life history
8
1. Chlorophylls – green pigments, embedded in thylakoid membrane. Chl a is the main player: used in all algae and land plants.
2. Carotenoids – brown, yellow, or red pigments. Hydrocarbons with or without an oxygen molecule
Algal pigments:
29
y yg= 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
Chlorophyta:- Chl: - Carotenoids: - Phycobilins:
Ochrophyta:- Chl:
Pigments
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Chl: - Carotenoids:- Phycobilins:
Rhodophyta:- Chl: - Carotenoids:- Phycobilins:
II. Algal characteristics for distinguishing divisions:
1. Pigments
2. Storage products
3. Cellular/plastid structure
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4. Motility (e.g. +/- flagella)
5. Life history
Storage products2 forms:alpha 1,4 linked = starches (Chlorophyta, Rhodophyta)
(e.g. floridean,amylopectin, amylosestarches)
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beta 1,3 linked = sugars (Ochrophyta)
(e.g. laminarin, chrysolaminarin, mannitol)
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Chlorophyta:Starches:
Ochrophyta:
Storage Products:
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Ochrophyta:Sugars:
Rhodophyta:Starches:
II. Algal characteristics for distinguishing divisions:
1. Pigments
2. Storage products
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3. Chloroplast structure
4. Motility (e.g. +/- flagella)
5. Life history
Chloroplast structure
Ochrophyta:Chlorophyta:
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Rhodophyta:
Chlorophyta:Membranes:
Thylakoids:
Ochrophyta:
Chloroplast Structure:
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Ochrophyta:Membranes:
Thylakoids:
Rhodophyta:Membranes:
Thylakoids:
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II. Algal characteristics for distinguishing divisions:
1. Pigments
2. Storage products
3 C llul r/pl stid structur
37
3. Cellular/plastid structure
4. Motility (e.g. +/- flagella)
5. Life history
To have or not to have…………….
Ochrophyta:Chlorophyta:
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Rhodophyta:
…….flagella
Chlorophyta:
Ochrophyta:
Flagella:
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Rhodophyta:
II. Algal characteristics for distinguishing divisions:
1. Pigments
2. Storage products
3 C llul r/pl stid structur
40
3. Cellular/plastid structure
4. Motility (e.g. +/- flagella)
5. Life history
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Algal life histories vary
Fertilization
Vegetative
Mitosis
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Reproduction
Meiosis
Algal life histories : Terminology to know and love
Spore (mitospore, meiospore):
Gamete:
Sporophyte:
Gametophyte:
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Haplontic:
Diplontic:
Alternation of Generations:Heteromorphic:
DiplohaplonticHaplodiplontic
Isomorphic:
Algal Life CyclesThree main patterns:1) Haplontic2) Diplontic3) Alternation of Generations
• Isomorphic• Heteromorphic
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Three main patterns:1) Haplontic2) Diplontic3) Alternation of Generations
• Isomorphic• Heteromorphic
Algal Life Cycles
44“animal-like” life history
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Algal Life CyclesThree main patterns:1) Haplontic2) Diplontic3) Alternation of Generations
• Isomorphic• Heteromorphic
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Algal Life CyclesThree main patterns:1) Haplontic2) Diplontic3) Alternation of Generations
• Isomorphic• Heteromorphic
46“haplodiplontic”
Algal Life CyclesThree main patterns:1) Haplontic2) Diplontic3) Alternation of Generations
• Isomorphic• Heteromorphic
47“diplohaplontic”
Chlorophyta:
Ochrophyta:
Life cycles:
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Rhodophyta:
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Example: Fucus
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Example: Ulva
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Example: Nereocystis
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