PLANTS AND LIGHT Plants 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 Chlorophylls – reflect green light chlorophyll a – gathers all light energy for light dependent reactions chlorophyll b Carotenes – orange pigment – reflect orange light Absorb light energy and transfer it to chlorophyll a 3. Xanthophylls – yellow pigment – reflects yellow

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