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BIO409H5 (1)

BIO409 lecture 1.docx

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University of Toronto Mississauga
Angela B Lange

BIO409 lecture 1 -Must get book (other book has 2 chapters online) Grading 2 tests: 30% Participation: 11% Labs (quizzes, reports and assignments): 59% Are Plant-environment-interactions important? -GEP (Gross ___ photosynthesis) -photosynthesis goes up during those months(may-oct) -this is photosynthesis of the entire forest Winter cease of photosynthetic CO upt2ke in the northern hemisphere causes seasonal change in atmospheric [CO ] 2 -annual cycle -CO decrease in increase, decrease during winter 2 -minimum in October, maximum in May -Sawtooth cycle -shows thats plant have responses to the environment Tropical Mopane: Seasonal downregulation of photosynthesis in response to drought Geographical Adaptation at the Leaf level: an evolutionary pattern Why does Photosynthesis change in response to environmental change? The concept of photostasis -the sigma lots of chlorophyll to absorb lots of energy -t rate of consumption -photostasis homeostasis for plants -imbalance created by increasing sources or sink capacities -Ek= irradiance where max. quantum yield equals photosynthetic capacity -sigma psIII = effective absorption cross section of PSII Photostasis: photosynthesis acclimates to balance the flow of energy from source to sink -downrate photosynthesis to match a decrease in consumption (winter) "-source" -increase of photosynthesis to match an incease in consumption of metabolic sinks "+sink" The First step in photosynthesis- absorption of light energy -two option after the light energy hits, either refelected off the leaf or light is allowed in -light is let in and Chlorphyll then has 3 options -photochemical processes with a final product of ATP and NADPH -Heat (nonphotochemical quenching) dissipating heat -florescence (680-700) -these are ways of getting rid of excess of energy Where it all takes place Protein complexes, including photosystems I and II are embedded in the thylakoid membrane of the chloroplast -stroma surrounds thylakoid -anything inside is lumen Chlorophylls and carotenoids vary in absorption spectra -chlorophyll and carotenoids vary in absorption spectra -* see where the peaks are and what color they absorb Funneling of excitation from the antenna system toward the reaction center Light and carbon reaction of photosynthesis occur in chloroplast -photostasis: electrons provided through source reactions (light-dep. reactions) need to be balanced by consumption of electrons though metabolic sink (calvin cycle) -generation of ATP and NADPH fuel the calvin cycle -NADP+ and ADP are required as electron and proton acceptors by the light reactions -CO fixed by rubisco and then is used to make carbohyrdates 2 -production of NADPH and ATP of light reactions must equal the capacity and use of NADPH and ATP in the dark reactions The Calvin Cycle takes place in the stroma and reduces inorganic carbon (CO ) and generates 2 carbohydrates Electrons link light dep. and Calcin cycle reactions -photostasis: electrons provided through source reactions (light-dep. reactions) need to be balanced by consumption of electrons through metabolic sink (calvin cycle) Light environment is diverse and variable -the distribution of sunlight at the top of a canopy and under the canopy -example: -total irradi
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