Algal Physiology I. Photosynthesis in algae II. Characteristics to distinguish algal divisions 1 I. Photosynthesis 2 1
PSU : Photosynthetic Unit = Antennae + rxn center Light reactions: solar energy is harvested and transferred into the chemical bonds of ATP and NADPH 3 4 2
Calvin Cycle: C fixation from CO 2 to sugar using energy from ATP and NADPH 5 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 6 3
Pigment Location 7 What light can be used for photosynthesis? 8 4
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 9 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 10 5
What s wrong with this picture? 11 What s wrong with this picture? 12 6
Algae have accessory pigments: Allow harvesting of light at middle wavelengths, then channel energy to Chl a 13 Algae have accessory pigments: Allow harvesting of light at middle wavelengths, then channel energy to Chl a PSU : Photosynthetic Unit = Antennae + rxn center 14 7
Algal accessory pigments: 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 15 How we study photosynthesis: The Ps/I curve 1. 1. Pmax = Maximum production 16 8
How we study photosynthesis: The Ps/I curve 1. 2. 1. Pmax = Maximum production 2. I k = Saturating irradiance (where initial slope meets Pmax) 17 How we study photosynthesis: The Ps/I curve 1. 3. 2. 1. Pmax = Maximum production 2. I k = Saturating irradiance 3. Gross photosynthesis = Total production 18 9
How we study photosynthesis: The Ps/I curve 1. 3. 4. 2. 1. Pmax = Maximum production 2. I k = Saturating irradiance 3. Gross photosynthesis = Total production 4. Net photosynthesis = Gross production Respiration 19 How we study photosynthesis: The Ps/I curve 1. 3. 4. 5. 2. 1. Pmax = Maximum production 2. I k = Saturating irradiance 3. Gross photosynthesis = Total production 4. Net photosynthesis = Gross production Respiration 5. I c = Compensation point: When photosynthesis equals respiration 20 10
How we study photosynthesis: The Ps/I curve 1. 6. 3. 4. 5. 2. 1. Pmax = Maximum production 2. I k = Saturating irradiance 3. Gross photosynthesis = Total production 4. Net photosynthesis = Gross production Respiration 5. I c = Compensation point: When photosynthesis equals respiration 6. Initial slope (alpha) = Indicative of photosynthetic efficiency 21 How we study photosynthesis: The Ps/I curve 1. 7. 6. 3. 4. 5. 2. 1. Pmax = Maximum production 2. I k = Saturating irradiance 3. Gross photosynthesis = Total production 4. Net photosynthesis = Gross production Respiration 5. I c = Compensation point: When photosynthesis equals respiration 6. Initial slope (alpha) = Indicative of photosynthetic efficiency 7. Photoinhibition = Damage to photosystems due to high irradiance 22 11
How we study photosynthesis: The Ps/I curve 1. 7. 6. 3. 4. 5. 2. 23 How we measure photosynthetic rates (primary productivity): Measure Oxygen release (Biological Oxygen Demand BOD): With electrodes using O 2 = O 2 meter or Chemical titration Use Light and Dark Bottles Dark Bottles measure Respiration Light Bottles measure Ps - Rs = Net photosynthesis Light Bottle O 2 + Dark Bottle O 2 = Gross photosynthesis Photosynthetic Rate measured as O 2 /g/hr 24 12
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 CO 2 measurement (by ph) C 14 isotope tracers Infrared gas analysis 25 II. Algal characteristics for distinguishing divisions: 1. Pigments 2. Storage products 3. Cellular/plastid structure 4. Motility (e.g. +/- flagella) 5. Life history 26 13
Algal pigments: 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 27 Pigments Chlorophyta: - Chl: - Carotenoids: - Phycobilins: Heterokontophyta: - Chl: - Carotenoids: - Phycobilins: Rhodophyta: - Chl: - Carotenoids: - Phycobilins: 28 14
II. Algal characteristics for distinguishing divisions: 1. Pigments 2. Storage products 3. Cellular/plastid structure 4. Motility (e.g. +/- flagella) 5. Life history 29 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) 30 15
Storage Products: Chlorophyta: Starches: Heterokontophyta: Sugars: Rhodophyta: Starches: 31 II. Algal characteristics for distinguishing divisions: 1. Pigments 2. Storage products 3. Chloroplast structure 4. Motility (e.g. +/- flagella) 5. Life history 32 16
Chloroplast structure Chlorophyta: Heterokontophyta: Rhodophyta: 33 Chloroplast Structure: Chlorophyta: Membranes: Thylakoids: Heterokontophyta: Membranes: Thylakoids: Rhodophyta: Membranes: Thylakoids: 34 17
II. Algal characteristics for distinguishing divisions: 1. Pigments 2. Storage products 3. Cellular/plastid structure 4. Motility (e.g. +/- flagella) 5. Life history 35 To have or not to have. Chlorophyta: Heterokontophyta: Rhodophyta:.flagella 36 18
Flagella: Chlorophyta: Heterokontophyta: Rhodophyta: 37 II. Algal characteristics for distinguishing divisions: 1. Pigments 2. Storage products 3. Cellular/plastid structure 4. Motility (e.g. +/- flagella) 5. Life history 38 19
Algal life histories vary Fertilization Mitosis Vegetative Reproduction Meiosis 39 Algal life histories : Terminology to know and love Spore (mitospore, meiospore): Gamete: Sporophyte: Gametophyte: Haplontic: Diplontic: Alternation of Generations: Heteromorphic: Diplohaplontic Haplodiplontic Isomorphic: 40 20
Algal Life Cycles Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations Isomorphic Heteromorphic 41 Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations Isomorphic Heteromorphic Algal Life Cycles animal-like life history 42 21
Algal Life Cycles Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations Isomorphic Heteromorphic 43 Algal Life Cycles Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations Isomorphic Heteromorphic haplodiplontic 44 22
Algal Life Cycles Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations Isomorphic Heteromorphic diplohaplontic 45 Life cycles: Chlorophyta: Heterokontophyta: Rhodophyta: 46 23
Example: Fucus 47 Example: Ulva 48 24
Example: Nereocystis 49 25