EXAM THREE - SUMMER 2013LECTURE 11 OBJECTIVES - PHOTOSYNTHESISPHOTOSYNTHESISROUTE BY WHICH VIRTUALLY ALL ENERGY ENTERS THE BIOSPHERE3CO2 + 6H2O ---> C3H6O3 + 3O2 +3H2O (IN THE PRESENCE OF LIGHT)1ST EVOLVED IN BACTERIACYANOBACTERIA: MODERN DAY PHOTOSYNTHETIC BACTERIAOXYGENIC PHOTOSYNTHESIS: EVOLVED 2.5 BILLION YRS AGOPRECEDED BY PHOTOSYNTHETIC BACTERIA USE ELECTRON DONORSOTHER THAN WATEREX. PURPLE SULFUR BACTERIA: USE H2S, ELEMENTAL SULFURIS BYPRODUCT RATHER THAN OXYGENOCCURS IN 2 SEPARATE RXNSLIGHT RXNTAKES PLACE ON THYLAKOID MEMBRANES OF THE CHLOROPLASTLIGHT CAPTURED BY CHLOROPHYLL LEADS TO ELECTRON TRANSPORT& FORMATION OF ATP & REDUCTION OF NADP --> NADPHABSORPTION SPECTRUM: LIGHT ABSORPTION PATTERN OF A PIGMENTACTION SPECTRUM: RANGE OF LIGHT THAT SPECIFIC LIGHT REQUIRINGPROCESS OCCURS DRIVEN BY RED & BLUE LIGHTPHOTOSYNTHETIC PIGMENTSCHLOROPHYLLA: CYANOBACTERIA & ALL PHOTOSYNTHETIC EUKARY.B: ACCESSORY PIGMENT, NOT DIRECTLY INVOLVED INENERGY TRANSDUCTION, SERVES TO BROADENRANGE OF LIGHT USEDCAROTENOIDSPROTECT CHLOROPLAST FROM PHOTOBLEACHINGANTIOXIDANTNEITHER CHLOROPHYLL B OR CAROTENOIDS CAN REPLACE CHLOROPHYLL A IN PHOTOSYSTEMSEMBEDDED IN THYLAKOID MEMBRANES: PHOTOSYSTEMSANTENNA COMPLEX: PERIPHERY, CAPTURES PHOTONSRXN CENTER: CENTER, SPLIT H202 PHOTOSYSTEMS2: WATER SPLIT TO O2 & 2H+1: REDUCES NADP TO NADPHATP IS MADE BETWEEN BOTH PHOTOSYSTEMSCALVIN CYCLE/DARK RXNTAKES PLACE IN THE STROMA OF THE CHLOROPLASTFLUID FILLED SPACEFIXES CO2 INTO CARBS USING ATP & NADPH FROM LIGHT RXNRUBISCO CARRIES OUT CO2 FIXATION & IS AN ENZYMECONVERTS A 5 CARBON SUGAR(RuBP) --> 2, 3 CARBON SUGAR(PGA) 6 TURNS ON CYCLE --> 1 GLUCOSEEXCESS GLUCOSE IS STORED AS STARCHPHOTORESPIRATIONRuBP + CO2 + H2ORubisco2 PGACO2 IS LOW, RUBISCO BINDS 02 & BREAKS DOWN RuBP TOGLYCOLATE & EVENTUALLY TO CO2REDUCES PHOTOSYNTHETIC EFFICIENCY BY 30-40%RUBISCO HAS DUAL ACTIVITY: CARBOXYLASE & OXYGENASEOXYGENASE --> PHOTORESPIRATION (UNWANTED)OCCURS IN PEROXISOME & MITOCHONDRIAWHEN TEMPERATURE IS HIGH, C3 PLANTS SUFFER FROM THISEX. WHEAT, OATS, RICEC4 PLANTSSOLUTION TO PHOTORESPIRATION PROBLEMEX. SUGAR CANE, MAIZE, TROPICAL PLANTSFIX CO2 --> 4 CARBON COMPOUND (MALATE)SPATIAL SEPARATION OF CO2 FIXATION & CALVIN CYCLEMESOPHYLL CELLS: SITE OF CO2 FIXATIONBUNDLE SHEATH CELLS: SITE OF CALVIN CYCLEMORE EFFICIENT THAN C3 AT HIGH TEMPS & MODERATELY DRY CONDITIONSCAM PLANTSC4 MODIFICATIONTEMPORAL SEPARATION OF CO2 FIXATION & CALVIN CYCLECO2 FIXATION: NIGHT, STOMATA OPENCALVIN CYCLE: DAY, STOMATA CLOSEDUSE MALATE TO FIX CO2EX. PINEAPPLE, CACTUSSAVE H20, DRY & HOT AREASLECTURE 12 OBJECTIVES - WATER & NUTRIENT TRANSPORTTRANSPIRATION:DEFINITION: water loss in plantsINEVITABLE ASPECT OF PHOTOSYNTHESIS IN LAND PLANTS: gaseous CO2 must go into solution in water in the plant cell wall prior to entering the cells, &evaporation occurs when air hits the water MAIN ORGAN OF WATER LOSS: leaves through the stomata (pores on the epidermis)AIDS PHOTOSYNTHESIS: by cooling plants, lowers tissue temperature (which increases efficiency for C3 plants)WATER MOVES THROUGH XYLEM: stacked vessels for high volume water transportCOHESION-TENSION THEORYTHEORY OF HOW THE FLUID MOVES IN THE XYLEMEVAPORATION & TRANSPIRATION: evaporation at the plant's surface produces a pull/tension that's transmitted to the roots by the cohesiveness of watermoleculesDRIVING FORCE: difference in relative humidity between the inside of the leaf &outside airHYDROGEN BOND INTERACTION: in water molecules, creates the constant waterstream to be pulled up the plantHUMIDITY: water moves from high potential to lower potentialex. if the leaves have a higher humidity, water leaves the leaves & watermoves up from the roots --> leavesEVIDENCE FOR THIS THEORY:1. NEGATIVE PRESSURES IN THE TRUNK & LEAVES CAN BE MEASURED2. STEM DIAMETERS SHRINK DURING THE DAY & INCREASE AT NIGHT: diameter shrinks at upper trunk slightly before lower trunk because the pull is coming from the topTRANSPIRATION STREAMDEFINITION: flow of water through the xylemWATER IS AVALIABLE THROUGH THE ROOTS, WATER IS ABSORBED PASSIVELY BY ROOTSMINERALS ALSO TRANSPORTED: ion uptake linked to transpiration & photosynthesisACTIVE: during the dayPASSIVE: during the nightSTREAM CAN BE BROKENCAVITATION(RUPTURE) OF WATER COLUMN PRODUCES AN EMBOLISM( AIR BUBBLE): can't move waterVESSELS: have perforation plates"open system"embolisms can spread TRACHEID:restricted to one tracheid; no perforation plateswater passes through bordered pit pairsair is prevented from spreading to adjacent tracheid by surface tensionof air-water meniscus spanning pores in pit membraneMAXIMUM HEIGHT OF TREES IS 350 FT: with more height there is a increasein tension --> increase in bubble chance ex. redwoodsTRANSPIRATION MUST BE REGULATEDTURGOR PRESSURE: maintains rigidity & keeps plant erectOPEN/CLOSE STOMATA:RESPOND TO..lightCO2 concentrationwaterOPENING OCCURS WHEN SOLUTES ARE ACTIVELY ACCUMULATEDIN GUARD CELLS THAT SURROUND STOMATAINCREASE IONS: water goes in, turgid guard cells &stoma openDECREASE IONS: water goes out, flaccid guard cells &stoma closedK+ AND CL- CHANNELS INVOLVEDGUARD CELLS:INNER(VENTRAL) WALL IS THICKER & MORE RIGID THAN OUTSIDE(DORSAL)RADIALLY-ORIENTED CELLULOSE MICROFIBRILS IN WALL:prevent lateral expansionINCREASE IN TURGOR PRESSURE CAUSES OUTER WALLS TO MOVE OUTWARD RELATIVE TO INNER WALL---> PORE OPENSDECREASE IN TURGOR PRESSURE --> PORES CLOSEFACTORS AFFECTING RATE OF TRANSPIRATIONHUMIDITYTEMPERATUREWINDSURFACE AREASTOMATES OPEN OR CLOSEDLEAF ADAPTATIONSEPIDERMIS LIMITS WATER LOSSCUTICLE:LAYER OF CUTIN(waxy substance), on outer wall of epidermal cellsIMPERVIOUS TO WATER & CARBON DIOXIDEPHOTOSYNTHETIC STEMSSUCCULENT LEAVESLEAVES REDUCED TO SPINESHAIRY LEAVES - TRICHOMESXEROPHYTE:PLANTS ADAPTED TO GROW IN DRY, ARID ENVIRONMENTMULTIPLE LAYER EPIDERMISSTOMATA ON UNDERSIDE SUNKEN IN W/ TRICHOME(root hairs)CUTICLEC4 & CAM PLANTS:SPECIAL ADAPTATIONS TO MAINTAIN PHOTOSYNTHESIS WHILE LIMITING TRANSPIRATIONhave opposite stomata openings than other plants MOVEMENT OF SUGARSVIA PHLOEMSOURCE (leaves/storage structures) --> SINKS (fruits or storage structures)SUCROSE IS TRANSPORTED SUGAR IN MOST PLANTSMAIN SINKSVEGETATIVE - GROWING TISSUEREPRODUCTIVE - FRUITAPHIDS:EVIDENCE OF SUGAR MOVEMENTPHLOEM FEEDERSPATHWAY:MESOPHYLL CELLS --> SIEVE TUBES THROUGH PLASMODESMATA & CELL WALLSREQUIRES ENERGYACTIVE TRANSPORT:VIA SUCROSE-PROTON CO-TRANSPORTTRANSPORT OF PROTONS OUT OF CYTOPLASM OF CELLS GIVES ENERGYFOR SUCROSE MOVEMENTSPRESSURE FLOW
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