Transcript light

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Did you know…
Chameleons often have tongues longer than
their bodies.
A worm is both male and female at the same
time (a hermaphrodite.)
“Why do leaves change color in the fall?” Article
1. What are annuals?
2. What are perennials?
3. What is the difference btwn deciduous trees &
evergreen trees? Give 1 example of each.
4. How do plants function during the summer?
5. What is the abscission layer of a leaf?
6. How does the abscission layer change in Fall?
7. List 4 types of pigments & tell which color we
see them as.
8. What causes leaves to change color in the fall?
1.
2.
3.
Annuals complete their life cycle in 1 growing
season. They “die” during winter, but seeds last
through the cold & sprout in the spring.
Perennials have life cycles of more than 2 yrs.
During winter, herbaceous parts (leaves/stems)
above ground die, but stored food
(wood/roots/bulbs) remains alive.
Deciduous trees (elms, oaks, & maples) shed
their leaves in fall. Evergreen/coniferous trees
(holly, pines, & firs) keep their waxy
needles/leaves through winter.
4.
5.
6.
During summer, leaves over-produce
glucose & store to prepare for winter.
Abscission layer of leaf: separation layer at
base of each leaf. Contains small tubes
carrying water to leaf & food from leaf to
other plant parts.
In fall, abscission layer swells & turns into
cork substance that blocks small carrier
tubes.
7.
8.
Carotene pigment appears orange.
Xanthophyll pigment appears yellow.
Anthocyanin pigment appears red & purple.
Chlorophyll pigment appears green.
When abscission layer swells, glucose/waste
become trapped in leaf. No new water can
reach leaf, causing chlorophyll to disappear.
As chlorophyll disappears, other pigments
already present in leaf become visible.
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To make glucose from light
◦ “photo-”: light
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+
“synthesis”: to make
Chem equation:
6CO2 + 6H2O
–light
C6H12O6 + 6O2
carbon dioxide+water —light glucose+oxygen
(reactants)
--reaction (products)
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Belgian physician (1643)
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Test: do plants grow by
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Results:
absorbing soil?
◦ Soil mass didn’t change
◦ Less water mass
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Conclusion: plants gain mass from water
http://www.youtube.com/watch?v=pdgkuT1
2e14
 English minister (1771)
 Test: how plants’ byproducts
affect other objects (candle)
 Results:
◦ Candle by itself = burned out
◦ Candle + mint leaf = didn’t burn out
 Conclusion: plants release invisible product
called oxygen (O2)
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Dutch scientist (1779)
Tested: how plants’ byproduct
changes when in light & dark
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Results: candle stayed lit only when plant
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Conclusion: light is necessary for oxygen to
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in sunlight
be produced
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Energy from sun
“White” light: mixture of ALL light
wavelengths/colors
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Absorb certain light wavelengths/energy
Reflect other wavelengths/energy
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Pigments in chloroplasts
Chlorophyll a & b absorb
blue-violet & red wavelengths
Green light is not absorbed
Green light is reflected =
plants look green
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http://www.youtube.com/watch?v=C1_uez5
WX1o
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1.
2.
Photosystems:
pigments absorb light
energy
Thylakoids: flattened sacs filled w/
photosystems
◦ Light-DEPENDENT rxns
2
5: Outer
3.
Granum: stack of
thylakoids
5: Inner
4.
5.
3
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Stroma: clear gel filling chloroplast
◦ Light-INDEPENDENT rxns
Bilayer: double-layered membrane
1.
Light-Dependent Rxn:
◦ Requires light
◦ Requires energy carriers (ATP & NADPH)
 Sun’s energy excites/heats e Electron carriers/“oven mitts” transport
excited/“hot” e◦ Occurs in photosystems/thylakoids
◦ Overall reactants: light/energy, H2O, ADP
◦ Overall products: O2, ATP
2.
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Light-Independent Rxn:
aka Calvin Cycle or “Dark” Rxn
Does NOT require light (light-independent)
Uses ATP (short-term energy) from lightdependent rxns to produce sugars (longterm energy)
Occurs in stroma
Overall reactants: CO2, ATP
Overall products: energy molecules (glucose
sugar), ADP
Water
1.
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Temp
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Enzymes work best btwn 0-35°C
Intensity & wavelength
of light:
3.
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More water = more PS
More intensity = more PS
Red & blue = more PS
PS incr until max rate
is reached