Lecture 6 and 7

Lecture 6 and 7 - Reminder from last Lecture Reminder The...

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Unformatted text preview: Reminder from last Lecture Reminder The structure/function of Chl adominated PS I and PSII reaction centers is the same in all phytoplankton groups. However, outer LHCs associated with However, these PS I and PS II antenna vary depending upon taxonomic group and give phytoplankto their characteristic colors. Eg. Red Tide Dinoflagellates colors. = LHCs Alexandrium Dinoflagellates in Dinoflagellates coastal Red Tide coastal 2 LHCs = some Chl a-Chl c- protein complexes Chl Lots of Peridinin-Chl a- protein complexes Lots Peridinin-Chl Photosynthesis Light-Dependent Reactions and Bio-optical Measures of Primary Production Predictive Modeling is based upon Mechanistic Understanding Stroma (fluid outside the thylakoids but inside the chloroplast) but NADPH2 H+ NADPH = e Light-Harvesting Pigment-protein Pigment-protein Complexes (LHCs) For PS II PS II Chemical Chemical electron acceptor acceptor INTERMEDIATE ELECTRON CARRIERS (IECs) Chemical Chemical electron acceptor acceptor IEC Ejects electron e IEC Ejects electron PS I LHCs For For PSI PSI 680 e IEC e 4e Lumen ( fluid in fully enclosed Lumen space inside the thylakoids) space 4e e 2H2O H2O splitting complex For every 8 photons absorbed, 1 O2 molecule + O2 + 4H “evolved” 4H Phytoplankton pigmentation evolved to absorb different types of UWL fields. Phytoplankton Measure of Spectral Irradiance, QPAR(λ )z = PFD= how many photons available for PS Measure Phyto absorption spectrum, aph(λ ) = what kinds of photons can be absorbed (cDOM) QPAR(λ )z x aph(λ ) = QPHAR(λ ), photosynthetically absorbed radiation (particles) = number of photons absorbed to drive photosynthesis QPHAR(λ ) 8 = maximum number of O2 molecules that could be evolved = maximum quantum efficiency for photosynthesis (φ max) aph(λ ) QPAR(λ ) For each photon of QPHAR(λ ), 1/8th or 0.125 molecules of O2 will be evolved 0.125 QPHAR(λ ) Bio-optical estimation of rates of primary production based upon optical measures only Bio-optical Rate of Primary Production = PP (umoles O2 evolved/mg Chl/hr), used to get phyto plankton specific rates = PP (umoles O2 evolved/m3/hr), used to get volume specific rates = PP (umoles O2 evolved/m2/hr), used to get integrated water column rates Upper limit of PP z,t = QPAR(λ )z,t x aph(λ z,t) x Where max = 0.125 φ max z,t Caveat: in situ φ at depth z and time t = operational φ is often much less than 0.125 and highly variable depending upon environmental and cellular conditions. z,t Today’s great challenge: Hunt for methods to measure/predict in situ φ Underwater gliders Optical moorings z,t Satellite: MODIS-AQUA Satellite: Absorption Products (APS) (APS) Photosynthesis Light-Dependent Reactions and Bio-optical Measures of Primary Production Stroma (fluid outside the thylakoids but inside the chloroplast) but NADPH H+ NADP = e Light-Harvesting Pigment-protein Pigment-protein Complexes (LHCs) For PS II PS II Chemical Chemical electron acceptor acceptor INTERMEDIATE ELECTRON CARRIERS (IECs) Chemical Chemical electron acceptor acceptor IEC Ejects electron e IEC Ejects electron 680 PS I LHCs For For PSI PSI e IEC e 4e Lumen ( fluid in fully enclosed Lumen space inside the thylakoids) space 4e e 2H2O H2O splitting complex For every 8 photons absorbed, 1 O2 molecule + O2 + 4H “evolved” 4H Chemical energy 2 PO4 PO4 ADP Pi =PO4 photophosphorylation H+ H+ PO4 3 PO4 Reducing Power NADPH H+ NADP ATP PO4 = e Chemical Chemical electron acceptor acceptor IEC e IEC Ejects electron PS I LHCs LHCs For For PSI PSI e IEC e H + H + O2 H+ H+ H+ H+ Photosynthesis (PS) Light reactions = Light dependent reactions Dark reactions = Light-independent reactions Optional review/details www.steve.gb.com/science/photosynthesis.html www.steve.gb.com/science/photosynthesis.html Generally 1 O2 molecule is evolved for 1 CO2 molecule fixed Gross Photosynthesis Respiration Gross Photosynthesis - Respiration = Net Photosynthesis (growth potential) Measuring Gas Exchange to estimate Photosynthetic rates and Primary Production. Whe photosynthe rate fromse ral e rim nts areplotte against light inte n sis s ve xpe e d nsity, the re is a photosynthe light re sult sis sponsecurve re O2 evolution (PSII) C02 uptake/fixation (Calvin cycle) P -I (photosynthesis-irradiance) curve = P-E (photosynthesis -energy) curve Why do all P-I curves first increase in proportion to increasing irradiance and Why then level off to an upper limit = maximum rate of photosynthesis? then ...
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