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8.2 Photosynthesis Overview

8.2 Photosynthesis Overview. Photosynthesis -plants use energy to change water and carbon dioxide into sugars and oxygen (waste product). Transpiration. Loss of water through leaves Lost water replaced by xylem What factors can increase this?. Gas exchange . Occur in spongy mesophyll

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8.2 Photosynthesis Overview

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  1. 8.2 Photosynthesis Overview Photosynthesis-plants use energy to change water and carbon dioxide into sugars and oxygen (waste product)

  2. Transpiration • Loss of water through leaves • Lost water replaced by xylem • What factors can increase this?

  3. Gas exchange • Occur in spongy mesophyll • Stomata (openings in leaves)-not left open; too much water lost • Only open to get enough photosynthesis • Stomata respond to pressure changes • High pressure-open low pressure-close • Open-day closed-night

  4. Adaptations to leaves • Thorns-no photosynthesis/stems carry it out • Pine-narrow leaves with waxy epidermis • Sunken stomata-reduce water loss • Rock plants-few stomata, dry conditions • Thick cuticles-prevent water loss • Pitcher plants-attract prey/insects give nutrition

  5. I. History of Photosynthesis • Jan van Helmont-found that most of the gain in mass of plants had come from water • Joe Priestley-realized a candle burned out when oxygen was not present. • Then realized the candle could be relit if a plant was placed in the jar • Plant produced oxygen

  6. Jan Ingenhousz-showed light was needed in order for Priestley’s experiment to work

  7. II. The Photosynthesis Equation Sunlight+ 6CO2 + 6H20 ----> C6H12O6 + 6 02 -plants use C6H12O6 (glucose) to make more complex carbohydrates like starch -includes two stages-Light dependent reaction and Calvin Cycle

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