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6.10 PHOTOSYNTHESIS
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DEFINITION
Photosynthesis is a process carriedout by green plants to synthesizeorganic compound (carbohydrates)from raw inorganicsubstances(carbon dioxide andwater) in the presence of sunlight
and chlorophyll.
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DEVELOPMENT OFPHOTOSYNTHESIS.ARISTOTLE
Soil had ability
to CONVERTdead ORGANICMATTER into
NUTRIENT.
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1640 - Jean Baptiste vanHelmount
Conduct experiment toinvestigate plant growth
Result: He conclude thatplant need WATER togrew NOT the SOIL.
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1640 - Jean Baptiste vanHelmount
WRONG ASSUMPTION
material that madeup the bark, wood,
roots and leavescame from thewater he had addedover the five years!
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1772 Joseph Priestley
Discover OXYGEN.
Green plant couldRESTORE OXYGEN.
And also capable ofSUPPORTINGcombustion andrespiration.
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1779 - Jan Ingenhousz
Discover that plants onlyRELEASE OXYGEN in thepresence of SUNLIGHT.
Only GREEN PLANTcould release oxygen.
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1779 - Jan Ingenhousz
He placed plantsunderwater in atransparent container.
undersides of their
leaves made bubblesin sunlight.
The same plants wereplaced in darkness,
NO BUBBLES form.
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Further development ofphotosynthesis
1780s - Jean Senebier
Carbon dioxide taken inby plant duringphotosynthesis.
1804 de Saussure
Showed water is requiredby photosynthesis.
1845 Robert Mayer
Plant convert SOLARENERGY into CHEMICALENERGY duringphotosynthesis.
1905 Blackman
Photosynthesis involves
2 principle reactions lightreaction & dark reaction.
1937 Robert Hill
Isolated chloroplast in awater + oxidizing agent
can release oxygen.
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PHOTOSYNTHESIS
SUBSTANCES REQUIRED
CARBON DIOXIDE
WATER
SUNLIGHT
SUBSTANCESPRODUCED
CARBOHYDRATE
OXYGEN
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LEAF STRUCTURE
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B. Leaf StructuresCuticle: waxy
layer; covers
upper surface Prevent excessive
water loss.
Cuticle + epidermalcell = upper epidermis
allows sunlight topenetrate leaf into thechloroplast
Veins:Lead downthe leaf, sideveins support
lamina.
2Guard
CellsSurround
eachStoma
Mesop
hy
ll
(Opening)
Leaf Cross-Section
Veins
Cuticle
Stoma
Stoma- singular
Stomata-plural
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Palisade Mesophyll:
cells actively carry outphotosynthesisbecause they containChloroplasts.
Spongy mesophyll Cells carry outphotosynthesis
Air spaces allowdiffusion of waterand air.
Vascular bundle
-made of xylem & floem.
-xylem transport
water&minerals.-floem transportcarbohydrate.
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Guard Cells
Guard cells:
cells that control openand close the stoma
Stomata: tiny pore, openings in
leafs surface.
When open:
GASEXCHANGE:
Allows CO2 in &
O2 out of leaf
TRANSPIRATION
: Allows excess
H2O out of leaf
Stoma
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Slide # 9
Stoma Open Stoma Closed
Guard Cells
Stoma
Function of Stomata
Guard Cells
CO2
O2 H2O
What
goes
in?
Whatgoes
out?
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ADAPTATION OF LEAVES
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Leaf mosaic manner
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ADAPTATION OF PLANT
IN LAND
1.NORMAL CONDITION(water is available)
- Upper epidermis has NONE/LITTLE STOMATA.
- Most STOMATA on lower epidermis.- Mesophyll cells contain a lot of chloroplast.
- MESOPHYTES
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IN LAND
2. DRY CONDITION
- LEAVES reduce to
NEEDLE SHAPE, FEWSTOMATA.
- SUNKEN STOMATA
- CHLOROPLAST inthe STEM.
- XEROPHYTES
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IN WATER
1.FLOATING
- STOMATA on UPPER
epidermis.- CHLOROPLASTconcentrated on uppermesophyll cells.
- leaves and stemshave air-filled cavities.
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2. SUBMERGE
- thin, small leavewithout waxy
cuticle.- chloroplast in bothleaves and stem.
- leaves and stemhave air-filledcavity.
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MECHANISM OF
PHOTOSYNTHESIS
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PHOTOSYNTHESIS
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2 STAGES: LIGHT REACTIONAND DARK REACTION
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STRUCTURE OFCHLOROPLAST
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LIGHT REACTION
Required light.
Taken place atgrana.
Involves photolyticreaction.
Produce ATP andhydrogen atoms.
End product =oxygen and water.
Raw material used =water
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DARK REACTION
NOT required light.
Taken place at stroma.
Involved biochemicalreaction.
Used ATP and hydrogenatom from light cycle.
End product = glucose +water.
Raw material used =carbon dioxide.
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PHOTOSYNTHESISEQUATIONS
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FACTORS AFFECTING
PHOTOSYNTHESIS
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FACTORS AFFECTING THERATE OF PHOTOSYNTHESIS
LIGHT INTENSITY.
CONCENTRATION OF CARBONDIOXIDE.
TEMPERATURE.
WATER.
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Lets look at this simulation.
http://www.saddleworth.oldham.sch.uk/
http://www.saddleworth.oldham.sch.uk/science/simulations/waterweed.htmhttp://www.saddleworth.oldham.sch.uk/science/simulations/waterweed.htm -
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LIGHT INTENSITY
Rate of photosynthesis is directlyproportional to light intensityupto a certain point.
WHY???
Limiting factors are
Concentration of carbon dioxide.
Temperature.
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LIGHT INTENSITY
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CONCENTRATION OFCARBON DIOXIDE
An increase in the concentration ofcarbon dioxide results in an increasein the rate of photosynthesis.
Limiting factors are
Light intensity
Temperature.
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CONCENTRATION OFCARBON DIOXIDE
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TEMPERATURE
Dark Reaction involved ENZYMES inbiochemical reactions.
Change in temperature effect theenzyme action.
Indirectly it will effect the rate ofphotosynthesis.
Increment of 10C, the rate ofphotosynthesis will double
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TEMPERATURE
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TEMPERATURE
Increment of 10C, the rate ofphotosynthesis double.
Optimum temperature 25C 30C.Max rate.
Further increase after optimumtemperature, rate of photosynthesis
decreased. WHY???
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WATER
Required in light reaction.
Insufficient of water, stomata closed.
Preventing the diffusion of carbondioxide into leaves.
Rate of photosynthesis decreased.
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THE DIFFERENCE IN THERATE OF
PHOTOSYNTHESIS INPLANTS THROUGHOUT
THE DAY
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Rate of photosynthesis increases andreaches max at noon.
Light intensity and temperature are
higher. From noon to midnight, rate of
photosynthesis decreased until it
becomes ZERO.
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INCREASING THEPRODUCTIVITY OF CROPSBASED ON THE FACTORS
AFFECTINGPHOTOSYNTHESIS..
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TROPICAL CLIMATE
Characteristic
Moderately high temperature.
Abundant rainfall.
Sunshine all year round.
Ideal for plant growth for all yearround.
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TEMPERATE CLIMATE
Characteristic
4 seasons a year.
Rate of photosynthesis high during summer.
Rate of photosynthesis low during winter.
To ensure year round crops supply, plant isgrown in GREENHOUSES where the lightintensity, temperature and water supply are
artificially control.
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GREENHOUSE
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