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 nm
wavelength (nm)
10-9 meter
meter!

3. Light: An Energy Waveform With Particle Properties Too
wavelength
visible spectrum nm
wavelength (nm)
10-9 meter
meter!

4. White light: all the colors humans can see at once

5. Which side of our brains are we using?
Which side of our brains are we using?

6. Leaf Pigments Absorb Most Colors
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
Tall
Thin
White/Yellow
Unexpanded leaves
Preserve reserves
Short
Stocky
Green
Expanded leaves
Use reserves
How deeply buried am I?
Make Hay! Gravity!

9. Phototropism Darwin 1860s Went: IAA
light growth toward act
Went: IAA
transduction by IAA differential transport
IAA
IAA
perception by zeaxanthin
growth response +

10. Photosynthesis: Review and Expansion
We have been hiding considerable truth from you!
Not 1 step…more like 50!
light
CO2 + H2O
O2 + CH2O
chlorophyll
Light Reactions: perhaps 25 steps
light
ADP + P +
NADP +
H2O O2
+ NADPH2
+ ATP
chlorophyll
Interdependent!
Calvin Cycle Reactions: perhaps 25 steps
AKA: Dark Reactions
ATP +
NADPH2 +
CO2
CH2O
+ NADP
+ ADP + P
light
In sum:
CO2 + H2O
O2 + CH2O
chlorophyll
The light and Calvin cycle reactions are interdependent…no dark reactions!

11. What wavelengths of light drive photosynthesis?
Photosynthetic Rate
100%
Action Spectrum
green light reflected
some still drives photosynthesis
visible spectrum nm
wavelength (nm)
Light beyond 700 nm has insufficient energy to drive photosynthesis

12. What intensities of light drive photosynthesis?
Reaction Rate
100%
Photosynthesis
add to reserve
grow
reproduce
Respiration
Using reserves and may die
Light Intensity (fc)
, ,000 fc
compensation point
The example plant shown here “breaks even” at an intensity we have in our homes…a house plant!

13. What intensities of light drive photosynthesis?
Reaction Rate
100%
Photosynthesis A
Photosynthesis B
Respiration
Shade tolerant plant dies in intense light!
Light Intensity (fc)
, ,000 fc
compensation points
The second example plant shown here cannot survive in our homes…it is a sun-loving crop plant!

14. Where in a CT landscape is the light intensity the brightest…the longest?
Ferns
Hosta
Impatiens
MOD. MOIST
COOL MOIST
Shade all Day!
downspout
House
AM Cool Shade
PM Hot Sun
AM Cool Sun
PM Warm Shade
Sun all Day!
HOT DRY!
MOD. DRY!
Daisies
Roses
Petunias PM AM

15. General Houseplants if Sheer Drapes
Where in the house is the light intensity the brightest…the longest? N W E S
House
Too Dark!
Sun Lovers
Shade Lovers
African Violets
Ferns
Philodendrons
General Houseplants
Greenhouse Effect!
General Houseplants if Sheer Drapes PM AM

16. USDA Hardiness Zones of “Lower 48” States
Note: Willimantic is Zone 6

17. Exposed MORE UNIFORM COLD
Where should plants be placed in a CT landscape for winter hardiness?
Winter Wind N W E S
Exposed MORE UNIFORM COLD
snow profile
ZONE 4-5
WINDWARD INSULATED
Shade all Day!
ZONE 5-6
House
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 PM AM

18. Plants measure the length of the night…not the length of the day.
Photoperiodism-Sensing Seasons by Daylength
Noctoperiodism?
Short Day Plant
Chrysanthemum
Poinsettia
Long Day Plant
Lettuce
Spinach
Long Night Plant?
Short Night Plant?
16 hr
8 hr
Summer (June 21)
vegetative
flowering
no change
16 hr
8 hr
Winter (December 21)
flowering
vegetative
reversed
8 hr W
10 sec
Night Interruption
vegetative
flowering
8 hr W
10 sec
Day Interruption
vegetative
flowering
Plants measure the length of the night…not the length of the day.

19. Photoperiodism-Does Light Wavelength Matter?
Short Day Plant
Long Day Plant
16 hr
8 hr
Control
flowering
vegetative
8 hr R
10 sec
Red 660nm Interruption
vegetative
flowering
8 hr FR
10 sec
Far-Red 730nm Interruption
flowering
vegetative
8 hr R
10 sec each
Sequences Ending in Red FR
vegetative
flowering
8 hr FR
10 sec each
Sequences Ending in Far-Red R
flowering
vegetative
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: Bermuda=11+ Sweet Spanish=15+
How long does light need to be on inside house?: Comp Point