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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