Plants Lab 8 Photosynthesis The Earth is an open system that requires energy input from the sun. This energy is channeled into organic molecules via photosynthesis. Photosynthesis Photons of light arrive at the Earth’s surface and are absorbed by pigments in the chloroplasts of algae and plants. Photosynthesis makes glucose and oxygen from carbon dioxide and water. 6 CO2 + 12 H2O Sunlight C6H12O6 + 6 H2O + 6 O2 Photosynthetic Pigments Pigments are molecules that absorb some photons in the light spectrum, and reflect others. Colors in plants are produced by the reflection of the light waves that are not absorbed. Photosynthetic Pigments Chlorophyll a and chlorophyll b are green pigments found in chloroplasts. Anthocyanins produce blue, purple, pink and dark red and are not involved in photosynthesis. Water soluble Carotenoids produce yellow, orange & bright red. Located in chloroplasts. Isolating Plant Pigments Paper Chromatography is a technique that allows us to isolate plant pigments based on solubility. Chlorophyll a (yellow-green) Chlorophyll b ( blue-green) Carotenes (orange-yellow) Xanthophylls (yellow) Leaf Anatomy Mesophyll cells are the cells that perform photosynthesis. Leaf Anatomy Mesophyll cells require carbon dioxide to photosynthesize and must get rid of oxygen. Stomata are openings in the leaf surface that allow gas exchange. Each stoma is surrounded by guard cells. Tropisms Tropisms are directional growth responses of plants to external stimuli. Phototropism – plant grows toward light. (roots away, shoots toward) Gravitropism – plant grows in response to gravity.