Algal Physiology I. Photosynthesis I. Photosynthesis in algae II. Characteristics to distinguish algal divisions 1 2 PSU : Photosynthetic Unit = Antennae + rxn center Light reactions: solar energy is harvested and transferred into the chemical bonds of ATP and NADPH 3 4 1
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 5 6 Pigment Location What light can be used for photosynthesis? 7 8 2
What light can be used for photosynthesis? PAR = photosynthetically active radiation = 400-700 nm Pigments: Primary 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 Must also deal with UV light (280-320 nm); damage DNA, proteins - B-carotene, aromatic amino acids absorb UVB 9 Reflects green why most plants appear green 10 What s wrong with this picture? What s wrong with this picture? 11 12 3
Algae have accessory pigments: Allow harvesting of light at middle wavelengths, then channel energy to Chl a Algae have accessory pigments: Allow harvesting of light at middle wavelengths, then channel energy to Chl a PSU : Photosynthetic Unit = Antennae + rxn center 13 14 Algal accessory pigments: How we study photosynthesis: The Ps/I curve 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 Pmax = Maximum production 15 16 4
How we study photosynthesis: The Ps/I curve How we study photosynthesis: The Ps/I curve 3. Pmax = Maximum production Ik= Saturating irradiance (where initial slope meets Pmax) Pmax = Maximum production Ik= Saturating irradiance 3. Gross photosynthesis = Total production 17 18 How we study photosynthesis: The Ps/I curve How we study photosynthesis: The Ps/I curve 3. 4. 3. 4. 5. Pmax = Maximum production Ik= Saturating irradiance 3. Gross photosynthesis = Total production 4. Net photosynthesis = Gross production Respiration Pmax = Maximum production Ik= Saturating irradiance 3. Gross photosynthesis = Total production 4. Net photosynthesis = Gross production Respiration 5. Ic = Compensation point: When photosynthesis equals respiration 19 20 5
How we study photosynthesis: The Ps/I curve How we study photosynthesis: The Ps/I curve 7. 6. 3. 4. 6. 3. 4. 5. 5. Pmax = Maximum production 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 Pmax = Maximum production 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 21 22 How we study photosynthesis: The Ps/I curve How we measure photosynthetic rates (primary productivity): 6. 3. 4. 7. 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 5. 23 24 6
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 II. Algal characteristics for distinguishing divisions: Pigments Storage products 3. Cellular/plastid structure 4. Motility (e.g. +/- flagella) 5. Life history 25 26 Algal pigments: Chlorophylls green pigments, embedded in thylakoid membrane. Chl a is the main player: used in all algae and land plants. Pigments Chlorophyta: - Chl: - Carotenoids: - Phycobilins: 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 - Chl: - Carotenoids: - Phycobilins: - Chl: - Carotenoids: - Phycobilins: 27 28 7
II. Algal characteristics for distinguishing divisions: Pigments Storage products 3. Cellular/plastid structure 4. Motility (e.g. +/- flagella) Storage products 2 forms: alpha 1,4 linked = starches (Chlorophyta, Rhodophyta) beta 1,3 linked = sugars (Heterokontophyta) (e.g. floridean, amylopectin, amylose starches) 5. Life history 29 (e.g. laminarin, chrysolaminarin, mannitol) 30 Storage Products: Chlorophyta: Starches: II. Algal characteristics for distinguishing divisions: Pigments Sugars: Storage products 3. Chloroplast structure 4. Motility (e.g. +/- flagella) Starches: 5. Life history 31 32 8
Chlorophyta: Chloroplast structure Chloroplast Structure: Chlorophyta: Membranes: Thylakoids: Membranes: Thylakoids: Membranes: Thylakoids: 33 34 II. Algal characteristics for distinguishing divisions: To have or not to have. Chlorophyta: Pigments Storage products 3. Cellular/plastid structure 4. Motility (e.g. +/- flagella) 5. Life history.flagella 35 36 9
Flagella: Chlorophyta: II. Algal characteristics for distinguishing divisions: Pigments Storage products 3. Cellular/plastid structure 4. Motility (e.g. +/- flagella) 5. Life history 37 38 Algal life histories vary Fertilization Algal life histories : Terminology to know and love Spore (mitospore, meiospore): Gamete: Mitosis Sporophyte: Vegetative Reproduction Gametophyte: Haplontic: Meiosis Diplontic: Alternation of Generations: Heteromorphic: Diplohaplontic Haplodiplontic 39 Isomorphic: 40 10
Algal Life Cycles Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations Isomorphic Heteromorphic Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations Isomorphic Heteromorphic Algal Life Cycles 41 animal-like life history 42 Algal Life Cycles Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations Isomorphic Heteromorphic Algal Life Cycles Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations Isomorphic Heteromorphic 43 haplodiplontic 44 11
Algal Life Cycles Three main patterns: 1) Haplontic 2) Diplontic 3) Alternation of Generations Isomorphic Heteromorphic Chlorophyta: Life cycles: diplohaplontic 45 46 Example: Fucus Example: Ulva 47 48 12
Example: Nereocystis 49 13