Transcript AG-GH-PS-01.461-11.1p Light and Temp Interaction

Light and Temperature
Interaction
Modified by Georgia Agricultural
Education Curriculum Office
June, 2002
August 2008
Fall Leaf Color
• cool temps - very bright
days
August 2008
Orange
• yellow, reds, purples and
browns
• chlorophyll cells die as
temperatures get cooler
August 2008
Yellow
• carotenoids
• after chlorophyll dies you
see the other pigments that
are always present
August 2008
Red-Purple
• anthocyanins
• not always present
• synthesized in cooler temps
• made from sugar molecules
August 2008
Brown
• tannins
• mask or show up more once
chlorophyll dies
• produced in the leaves
August 2008
Leaf Fall
• need an abscission layer
• leaf can no longer
translocate carbohydrates
out of the leaf
August 2008
Bright Days
• lots of carbohydrates in the
leaf
• anthocyanins get brighter
color
August 2008
The Key……
• cool, short days
August 2008
Greenhouse Effect
• short, high energy wave
lengths of light from sun
enters house
• absorbed by structures and
plants
August 2008
Greenhouse Effect
• plants re-radiate green light
in longer waves
• long waves do not have as
much energy as the short
waves
August 2008
Greenhouse Effect
• longer waves do not have
enough energy to escape
from the house
• result is heat
August 2008
Greenhouse Effect
• this is how the earth is
heated
• long waves cannot escape
through the clouds
• cloudy nights are warmer
August 2008
Light
• energy - electromagnetic
radiation
• wavelengths - distance from
peak to peak
• measured in nanometers
“NM”
August 2008
Far Red
• color plants use
August 2008
Infra Red
• heat energy
August 2008
Visible light
• light quality - color
• quantity - intensity, how
bright
• duration - photoperiod
August 2008
Quality
• blue - 400-510 NM
• cell elongation
• photosynthesis - chlorophyll
absorbs red and blue light
August 2008
Quality
• phototropism - plant tends
to grow or bend toward a
light source
August 2008
Red
• photosynthesis
• stimulates branching
• encourage growth of
auxiliary buds
August 2008
Red
• phytochrome - light
absorbing pigment
• seed germination in
photoblastic seeds
August 2008
Red
• flowering responses
• photoperiod
August 2008
Far Red
• filters through leaf
• inhibits branching
phytochrome
reactions - inhibits
germination of
photoblastic seeds
August 2008
Far red
• promotes stem elongation
August 2008
Yellow - Green
• does not effect plants
August 2008
Intensity
• measured in foot candles
• amount per unit area on
plant
August 2008
Plants
• shade loving
• too much sun - leaf burn
• dehydrate
• kill chlorophyll
August 2008
Plants
• sun loving
• low light, pale color
• new leaves are small
• lack vigor
August 2008
Plants
• don’t flower properly if at all
August 2008
Light
• Light Compensation Point ”LCP”
• light intensity where rate of
photosynthesis = the rate of
respiration
August 2008
LCP
• Lowest intensity you can
grow a plat at
• If a plant is grown below this
level, respiration will be
greater than photosynthesis
August 2008
LCP
• plant will die
• for a plant to grow
photosynthesis must be
greater than respiration
August 2008
Acclimitization
• preparing plant for lower
light intensity conditions
• expose to lower light
intensity
August 2008
Artificial Lights
• Incandescent
• far red, red - elongation
• low blue
• 80% of emitted radiation is
heat
August 2008
Incandescent
• 20% visible light
• 12% utilized by plant
August 2008
Flourescent
• red, blue
• 36% heat energy
• 22% light used by plant
• spectral flexibility
August 2008
Flourescent
• can change the quality of
the light by changing the
coating on inside of bulbs
• Cool White - Ca
Halophosphate
August 2008
“Gro-Lux”
• coated with Mg
Fluorogerminate
• not as long life as cool
white, 30X more expensive
August 2008
Metal Halide
• increase light intensity
August 2008
Low Pressure
Sodium
• yellow glow
• energy efficient
• yellow - orange light
August 2008
High Pressure
Sodium
• red, blue light
• energy efficient
August 2008
Photoperiod
• length or duration of the
light period
• biological measurement of
relative length of light and
dark periods
August 2008
Photoperiod
• effects
• flowering
• leaf abscission
• dormancy - acclimate for
winter
August 2008
Effects…..
• Sex expression
• runner formation
• tuber formation
• bulb formation
August 2008
Short Day Plants
• flower when day length is
shorter
• the dark period is critical
• it’s dark longer than it is light
August 2008
Short Day Plants
• examples
• Chrysanthemum
• Christmas Cactus
• Poinsettia
August 2008
Long Day Plants
• flower when days are long
and nights are short
• example: lettuce, radish,
petunias
August 2008
Facilitative Long Day
• flower any period
• if long day - flowering is
enhanced
• examples - tomato, begonia
August 2008
Day Neutral
• flower under long or short
day lengths
• example: African Violet
August 2008
Poinsettias
• use night interrupted lighting
• turn on artificial lights from
10 p.m. to 2 a.m.
• splits up the dark period
August 2008
Poinsettias
• cyclic lighting from 10 p.m.
to 2 a.m.
• lights on for 6 minutes and
off for 24 minutes
August 2008