6.9 photosynthesis

8/6/2019 6.9 Photosynthesis

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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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6.9 photosynthesis

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