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Algal Physiology

I. Photosynthesis in algaeII. Characteristics to distinguish algal

divisions

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I. Photosynthesis

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Light reactions: solar energy is harvested and transferred into the chemical bonds of ATP and NADPH

“PSU” : Photosynthetic Unit = Antennae + rxn center

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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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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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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

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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

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tic R

ate

How we study photosynthesis: The P-E curve

O2 /g/hr

Ph

oto

syn

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tic R

ate

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Light Intensity

P

How we study photosynthesis: The P-E curve

2.

O2 /g/hr

ho

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nth

etic

Ra

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+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.

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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 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.

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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 efficiency5. Ik= Saturating irradiance6. Gross photosynthesis = Total production

1. Light Intensity

P 0-

5.

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How we study photosynthesis: The P-E curve

2.

O2 /g/hr

ho

tosy

nth

etic

Ra

te

+0

2.

3.4. 6. 7.

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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 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.

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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

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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:

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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

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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

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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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