1

1

Algal Physiology

I. Photosynthesis in algae II. Characteristics to distinguish algal

divisions

2

I. Photosynthesis

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

5

Calvin Cycle: C fixation from CO2 to sugar using energy from ATP and NADPH

6

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

7

Pigment Location

8

What light can be used for photosynthesis?

3

9

What light can be used for photosynthesis? PAR = photosynthetically active radiation = 400-700 nm

Must also deal with UV light (280-320 nm); damage DNA, proteins - B-carotene, aromatic amino acids absorb UVB

10

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 the blue and far-red regions

Reflects green why most plants appear green

11

What’s wrong with this picture?

12

What’s wrong with this picture?

4

13

Algae have accessory pigments: Allow harvesting of light at “middle” wavelengths, then channel energy to Chl a

14

Algae have accessory pigments: Allow harvesting of light at “middle” wavelengths, then channel energy to Chl a

“PSU” : Photosynthetic Unit = Antennae + rxn center

15

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

Algal accessory pigments:

16

How we study photosynthesis: The Ps/I curve

1. Pmax = Maximum production

1.

5

17

How we study photosynthesis: The Ps/I curve

1. Pmax = Maximum production 2. Ik= Saturating irradiance (where initial slope meets Pmax)

1.

2.

18

How we study photosynthesis: The Ps/I curve

1. Pmax = Maximum production 2. Ik= Saturating irradiance 3. Gross photosynthesis = Total production

1.

3.

2.

19

How we study photosynthesis: The Ps/I curve

1. Pmax = Maximum production 2. Ik= Saturating irradiance 3. Gross photosynthesis = Total production 4. Net photosynthesis = Gross production – Respiration

4.

1.

3.

2.

20

How we study photosynthesis: The Ps/I curve

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

4.

1.

3.

2. 5.

6

21

How we study photosynthesis: The Ps/I curve

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

4.

1.

3.

2. 5.

6.

22

How we study photosynthesis: The Ps/I curve

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 7. Photoinhibition = Damage to photosystems due to high irradiance

4.

1.

3.

2. 5.

6.

7.

23

How we study photosynthesis: The Ps/I curve

1.

4.3.

2.5.

6.

7.

1.

4.3.

2.5.

6.

7.

4.3.

2.5.

6.

7.

24

How we measure photosynthetic rates (primary productivity):

• Measure Oxygen release (Biological Oxygen Demand – BOD):

• 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

• Photosynthetic Rate measured as O2 /g/hr

7

25

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

• Other methods • CO2 measurement (by pH) • C14 isotope tracers • Infrared gas analysis

26

II. Algal characteristics for distinguishing divisions: 1. Pigments 2. Storage products 3. Cellular/plastid structure 4. Motility (e.g. +/- flagella) 5. Life history

27

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 = 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

Algal pigments:

28

Chlorophyta: - Chl: - Carotenoids: - Phycobilins: Heterokontophyta: - Chl: - Carotenoids: - Phycobilins: Rhodophyta: - Chl: - Carotenoids: - Phycobilins:

Pigments

8

29

II. Algal characteristics for distinguishing divisions: 1. Pigments 2. Storage products 3. Cellular/plastid structure 4. Motility (e.g. +/- flagella) 5. Life history

30

Storage products 2 forms: alpha 1,4 linked = starches (Chlorophyta, Rhodophyta) beta 1,3 linked = sugars (Heterokontophyta)

(e.g. floridean, amylopectin, amylose starches)

(e.g. laminarin, chrysolaminarin, mannitol)

31

Chlorophyta: Starches: Heterokontophyta: Sugars: Rhodophyta: Starches:

Storage Products:

32

II. Algal characteristics for distinguishing divisions: 1. Pigments 2. Storage products 3. Chloroplast structure 4. Motility (e.g. +/- flagella) 5. Life history

9

33

Chloroplast structure

Rhodophyta:

Heterokontophyta: Chlorophyta:

34

Chlorophyta: Membranes: Thylakoids: Heterokontophyta: Membranes: Thylakoids: Rhodophyta: Membranes: Thylakoids:

Chloroplast Structure:

35

II. Algal characteristics for distinguishing divisions: 1. Pigments 2. Storage products 3. Cellular/plastid structure 4. Motility (e.g. +/- flagella) 5. Life history

36

To have or not to have…………….

Rhodophyta:

Heterokontophyta: Chlorophyta:

…….flagella

10

37

Chlorophyta: Heterokontophyta: Rhodophyta:

Flagella:

38

II. Algal characteristics for distinguishing divisions: 1. Pigments 2. Storage products 3. Cellular/plastid structure 4. Motility (e.g. +/- flagella) 5. Life history

39

Algal life histories vary

Fertilization

Vegetative

Reproduction

Meiosis

Mitosis

40

Algal life histories : Terminology to know and love

Spore (mitospore, meiospore): Gamete: Sporophyte: Gametophyte: Haplontic: Diplontic: Alternation of Generations: Heteromorphic: Diplohaplontic Haplodiplontic Isomorphic:

11

41

Algal Life Cycles Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations

• Isomorphic • Heteromorphic

42

Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations

• Isomorphic • Heteromorphic

“animal-like” life history

Algal Life Cycles

43

Algal Life Cycles Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations

• Isomorphic • Heteromorphic

44 “haplodiplontic”

Algal Life Cycles Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations

• Isomorphic • Heteromorphic

12

45 “diplohaplontic”

Algal Life Cycles Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations

• Isomorphic • Heteromorphic

46

Chlorophyta: Heterokontophyta: Rhodophyta:

Life cycles:

47

Example: Fucus

48

Example: Ulva

13

49

Example: Nereocystis