Processes affected by CO 2 1) Pathways that consume CO 2 2) pathways that release CO 2

Processes affected by CO2

1) Pathways that consume CO2

2) pathways that release CO2

3) transpiration & stomatal number

C4 and CAM photosynthesisAdaptations that reduce PR & water lossBoth fix CO2 with a different enzyme

C4 and CAM photosynthesisAdaptations that reduce PR & water lossBoth fix CO2 with a different enzymelater release CO2 to be fixed by rubiscouse energy to increase [CO2] at rubisco

C4 and CAM photosynthesisAdaptations that reduce PR & water lossBoth fix CO2 with a different enzymelater release CO2 to be fixed by rubisco

use energy to increase [CO2] at rubiscoC4 isolates rubisco spatially (e.g. corn)

C4 and CAM photosynthesisAdaptations that reduce PR & water lossBoth fix CO2 with a different enzymelater release CO2 to be fixed by rubiscouse energy to increase [CO2] at rubiscoC4 isolates rubisco spatially (e.g. corn)CAM isolates rubisco temporally (e.g. cacti)

C4 and CAM photosynthesisC4 isolates rubisco spatially (e.g. corn)CAM isolates rubisco temporally (e.g. cacti)Advantages: 1) increases [CO2] at rubisco

C4 and CAM photosynthesisAdvantages: 1) increases [CO2] at rubisco

reduces PRprevents CO2 from escaping


reduces PRCO2 compensation point where CO2 uptake by PS = CO2 loss by “dark” respiration is 20-100 ppm in C3

C4 and CAM photosynthesisCO2 compensation point where CO2 uptake by PS = CO2 loss by “dark” respiration is 20-100 ppm in C3 0-5 ppm in C4 & CAM

C4 and CAM photosynthesisCO2 compensation point where CO2 uptake by PS = CO2 loss by “dark” respiration is 20-100 ppm in C3 0-5 ppm in C4 & CAMC4 and CAM also get saturated at lower pCO2


2) reduces water loss

C4 and CAM photosynthesisreduces water loss: don't need to open stomata as wideC3 plants lose 500 -1000 H2O/CO2 fixed

C4 plants lose 200 - 350CAM plants lose 50 - 100

C4 photosynthesis = spatial isolationC4 plants have Kranz anatomyMesophyll cells fix CO2 with PEP carboxylase

Bundle sheath cells make CH20 by Calvin cycle

C4 photosynthesis = spatial isolationC4 plants have Krantz anatomyMesophyll fix CO2 with PEP carboxylase

Send 4C product to B-S cell

C4 photosynthesis = spatial isolationB-S cells convert 4C to pyruvate releasing CO2 Calvin cycle fixes itChange pyruvate to PEP in mesophyll

C4 photosynthesis = spatial isolationB-S cells convert 4C to pyruvate releasing CO2 Calvin cycle fixes itChange pyruvate to PEP in mesophyllHas evolved independently>50 times!

C4 photosynthesis = spatial isolationHas evolved independently >50 times!Found in 18 families: both monocots & dicotsSome have C3 and C4 spp!

C4 photosynthesis = spatial isolationHas evolved independently>50 times!Found in 18 families:both monocots & dicotsSome have C3 and C4 spp!3 ways to shuttle C!

C4 photosynthesis = spatial isolation3 ways to shuttle C!All generate C4 acid inMesophyll & release CO2

in BS, but details vary

C4 photosynthesis = spatial isolationHas evolved independently >50 times!3 ways to shuttle C!Can occur w/in same cell! 3 diff spp do it 3 diff ways!

C4 photosynthesis = spatial isolationBenefits over C3

1) no PR2) less water loss



DisadvantageC4 use 30 ATP/ glucose; C3 use 18 ATP



DisadvantageC4 use 30 ATP/ glucoseC3 use 18 ATPLower Quantum efficiency

C4 photosynthesis = spatial isolationC4 use 30 ATP/ glucose; C3 use 18 ATP

At high T C4 grow betterAt high CO2 C3 grow betterBoth T and CO2 are going up!Hard to predict whichwill do better!

Crassulacean acid metabolism (CAM) Also uses C3 & C4 pathwaysUses C4 pathway at night: open stomata, let CO2 in

Close stomata & use C3 pathway during day

Crassulacean acid metabolism (CAM) At night open stomata, let CO2 in

Fix with PEP carboxylasebuild up C4 acidsall nightstored invacuole

Crassulacean acid metabolism (CAM) During day

close stomatadecarboxylate stored C4 acids fix CO2 using Calvin cycle

Crassulacean acid metabolism (CAM) advantages 1) no PR

2) minimal water loss3) photosynthesize when have lots of energy

Crassulacean acid metabolism (CAM) advantages 1) no PR

2) minimal water loss3) photosynthesize when have lots of energy

disadvantages1) can’t store much C4 acid2) uses lots of energy

Crassulacean acid metabolism (CAM) CAM is mainly used in dry environmentsSome aquatic plants do CAM

Crassulacean acid metabolism (CAM) Some aquatic plants do CAMTake up CO2 at night when concentration is higher: can be very low during the day!also some in tropical rainforests! >20,000 CAM spp!

Crassulacean acid metabolism (CAM) CAM is mainly used in dry environmentsFacultative CAM induce CAM during drought, do C3 when humid

Crassulacean acid metabolism (CAM) CAM is mainly used in dry environmentsFacultative CAM induce CAM during drought, do C3 when humidInactivate PEPC & openstomatanormally

Crassulacean acid metabolism (CAM) CAM is mainly used in dry environmentsFacultative CAM induce CAM during drought, do C3 when humidInactivate PEPC & openstomatanormallyCan tell by 13C

Crassulacean acid metabolism (CAM) Can tell by 13C• rubisco discriminates against 13C, so C3 plants have 13C of -280/00 if it can choose

• CAM & C4 have 13C of -140/00 because 13C diffuses more slowly


• CAM & C4 have 13C of -140/00 because 13C diffuses more slowly•Can tell if sugar came from C3 or C4/CAM by 13C


• CAM & C4 have 13C of -140/00 because although use up most CO2 in leaf 13C diffuses more slowly

•Can tell if sugar came from C3 or C4/CAM by 13C• Also tells about stomatal opening &water use efficiency

Processes affected by [Sugar]

Energy BiosynthesisStorageStructureOsmotic regulation

Signaling molecules

Processes affected by [Sugar]

Processes affected by [Sugar]1) Flowering: adding sucrose promotes early flowering

Processes affected by [Sugar]1)Flowering: adding sucrose promotes early flowering•[Sucrose] @apex in induction

Processes affected by [Sugar]1)Flowering: adding sucrose promotes early flowering•[Sucrose] @apex in induction•affects FT & LFY expression,also mir399

Processes affected by [Sugar]1)Flowering2)Photosynthesis

Processes affected by [Sugar]Photosynthesis

• Sugar turns downlight & dark rxns


• Sugar turns downlight & dark rxns• Represses rbcS & CAB genes


• Sugar turns down light & dark rxns• Sensed by hexokinase: acts as both an enzyme and a

sensor• Catalytically-inactive mutants still sense glucose!• Form complex in nucleus with subunits of the

proteasome and of the vacuolar H+ pump!

HXK1/GIN2 Flavonoid synthesis

Cell wall synthesis

Cytokinin signaling Auxin signaling Light signaling Ca2+ signaling

ROS scavenging / Detoxification Antioxidant protection

Sucrose metabolismStarch biosynthesisRespiration

Nitrogen metabolism

Fatty acid synthesis &mobilization

Defense

PhotosynthesisPhotorespiration

AtHXK1-Dependent Gene Expression

WT vs. gin2

Processes affected by [Sugar]Photosynthesis• Sugar turns down light & dark rxns• Affects partitioning inside cells• 1 in 6 G3P becomes (CH2O)n • either becomes starch in cp (to store in cell)

Processes affected by [Sugar]Photosynthesis• Sugar turns down light & dark rxns• Affects partitioning inside cells• 1 in 6 G3P becomes (CH2O)n • either becomes starch in cp (to store in cell)• or is converted to

DHAP & exported to cytoplasm to make sucrose

Processes affected by [Sugar]Photosynthesis• Sugar turns down light & dark rxns• Affects partitioning inside cells• 1 in 6 G3P becomes (CH2O)n • either becomes starch in cp (to store in cell)• or is converted to

DHAP & exported to cytoplasm to make sucrose•Pi/triosePO4 antiporter only trades triosePO4 for Pi:mechanism to regulate PS


• Sugar turns down light & dark rxns• Affects starch accumulation


• Sugar turns down light & dark rxns• Affects starch accumulation & degradation

Processes affected by CO 2 1) Pathways that consume CO 2 2) pathways that release CO 2

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