Light

1
Light

• The Source of all Biological Energy
• Trapped in Photosynthesis
• Used to determine Seasons

2
Light An Energy Waveform With Particle
Properties Too
wavelength
violet
blue
green
yellow
orange
red
400 500 600
700 nm
wavelength (nm)
10-9 meter
0.000000001 meter!
3
Light An Energy Waveform With Particle
Properties Too
wavelength
visible spectrum
400 500 600
700 nm
wavelength (nm)
10-9 meter
0.000000001 meter!
4
White light all the colors humans can see at once
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Which side of our brains are we using?
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White Light
Green is reflected!
Leaf Pigments Absorb Most Colors
7
Light An Energy Waveform With Particle
Properties Too
amplitude brightness intensity
Many metric units for different purposes We will
use an easy-to-remember English unit foot-candle
0 fc darkness 100 fc living room 1,000 fc
CT winter day 10,000 fc June 21, noon, equator,
0 humidity
8
Photomorphogenesis
light
form
origin
process
Growth in Dark Etiolated
Growth in Light Normal
Short Stocky Green Expanded leaves Usereserves
Tall Thin White/Yellow Unexpanded leaves Preserve
reserves
How deeply buried am I?
Make Hay!Gravity!
http//botit.botany.wisc.edu16080/images/130/Trop
isms/Etiolation/Etiolated_-_light_beans_MC_.jpg
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Phototropism
Darwin 1860s
light growth toward act
Went IAA
transduction by IAA differential transport
perception by zeaxanthin
growth response

http//www.ppdl.purdue.edu/ppdl/images/coleoptile3
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10
Photosynthesis Review and Expansion
We have been hiding considerable truth from
you! Not 1 stepmore like 50!
light
CO2 H2O
O2 CH2O
chlorophyll
Light Reactions perhaps 25 steps
light
H2O
ATP
NADP
ADP P
NADPH2
O2
chlorophyll
Interdependent!
Calvin Cycle Reactions perhaps 25 steps
AKA Dark Reactions
CO2
CH2O
NADPH2
NADP
ATP
ADP P
light
In sum
CO2 H2O
O2 CH2O
chlorophyll
The light and Calvin cycle reactions are
interdependentno dark reactions!
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What wavelengths of light drive photosynthesis?
Action Spectrum
green light reflected
some still drives photosynthesis
visible spectrum
400 500 600
700 nm
wavelength (nm)
Light beyond 700 nm has insufficient energy to
drive photosynthesis
12
What intensities of light drive photosynthesis?
Photosynthesis
add to reserve grow reproduce
Respiration
Using reserves and may die
compensation point
The example plant shown here breaks even at an
intensity we have in our homesa house plant!
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What intensities of light drive photosynthesis?
Photosynthesis A
Photosynthesis B
Respiration
Shade tolerant plant dies in intense light!
compensation points
The second example plant shown here cannot
survive in our homesit is a sun-loving crop
plant!
14
Where in a CT landscape is the light intensity
the brightestthe longest?
Ferns Hosta Impatiens
MOD. MOIST
COOL MOIST
Shade all Day!
AM Cool Shade PM Hot Sun
AM Cool Sun PM Warm Shade
Sun all Day!
HOT DRY!
MOD. DRY!
Daisies
Roses Petunias
15
Where in the house is the light intensity the
brightestthe longest?
Too Dark!
Shade Lovers
Sun Lovers
African Violets Ferns Philodendrons
General Houseplants
Greenhouse Effect!
General Houseplants if Sheer Drapes
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USDA Hardiness Zones of Lower 48 States
Note Willimantic is Zone 6
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Where should plants be placed in a CT landscape
for winter hardiness?
Exposed MORE UNIFORM COLD
ZONE 4-5
WINDWARD INSULATED
Shade all Day!
ZONE 5-6
AM Cool Shade PM Hot Sun
AM Cool Sun PM Warm Shade
ZONE 6-7
ZONE 2-3
Sun all Day!
ExposedFREEZE DRY
LEEWARD INSULATED
18
Photoperiodism-Sensing Seasons by Daylength
Noctoperiodism?
Long Night Plant?
Short Night Plant?
Plants measure the length of the nightnot the
length of the day.
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Photoperiodism-Does Light Wavelength Matter?
Short Day Plant
Long Day Plant
660 nm
Plants use Phytochrome to sense Night Light
Status.

Pr
Pfr
Pfr present for significant time in night blocks
flowers.
730 nm
20
Photoperiod Applications
Chrysanthemum Story Poinsettia Story LDP Lettuce
Problem Equinoxes LDP Onions Bermuda11 Sweet
Spanish15 How long does light need to be on
inside house? Comp Point