Download PLANTS AND LIGHT

PLANTS
LIGHT
Plants AND
and Light
(Photosynthesis)
(photosynthesis)
Autotrophs
Photoautotrophs: use light
to make food – plants,
cyanobacteria, algae
Chemoautotrophs: use
chemicals to make food –
bacteria by hydrothermal
vents in ocean (H2S)
Electromagnetic Spectrum
Light Energy
Sunlight ----radiation energy
----travels in waves (photons)
----mixture of all wavelengths of
light
Visible Spectrum: the different colors of light
that we perceive as white light
R O Y G B I V
(Low Energy ------------------- High Energy)
(Longer Wavelength----ShorterWavelength)
When light strikes matter
Some energy is absorbed
In photosynthetic
organisms – they take this
energy and store it in
chemical bonds – glucose
Some energy is reflected –
color you see is the color
that is reflected
Absorption Spectrum
The different colors or wavelengths of light
absorbed by a particular pigment
Red object --> reflects red --> absorbs
OYGBIV
Different for each pigment
Absorption Spectrum for Leaf Pigments
Photosynthetic Pigments
1.Chlorophylls – reflect green light
chlorophyll a – gathers all light energy for light
dependent reactions
chlorophyll b
2.Carotenes – orange pigment – reflect orange
light
Absorb light energy and transfer it to chlorophyll a
3. Xanthophylls – yellow pigment – reflects
yellow
Absorb light energy and transfer it to chlorophyll a
Questions ???
•Why are there so many pigments?
–So more wavelengths of light can be absorbed
and used for photosynthesis
• When do you see the carotenes and
xanthophylls?
–In the fall when the chlorophyll breaks down
• What causes the chlorophyll to break
down?
– Shorter daylight hours; cooler temperatures