Plants

• Photosynthesis


  The way that plants make their food from sunlight
• Chloroplasts


  • Tiny green structures in plant cells where photosynthesis occurs
  • Use light energy to turn carbon dioxide and water into glucose and oxygen
• Photosynthesis


  CO2 + H2O → C6H12O6 + O2
• To balance the photosynthesis equation, put a 6 in front of everything apart from the glucose
• Glucose


  The food made by plants through photosynthesis, which is the starting point to make other things the plant needs
• Endothermic reaction


  Photosynthesis takes in energy
• Limiting factors for photosynthesis

  • Temperature
  • Light
  • Carbon dioxide
• As light intensity increases


  The rate of photosynthesis increases, but then flattens out as something else becomes limiting
• As carbon dioxide concentration increases


  The rate of photosynthesis increases, but then flattens out as something else becomes limiting
• Inverse square law


  The intensity of light decreases as the distance from the light source increases, because the light is spread over a larger area
• Xylem


  Tubes that transport water up the plant
• Xylem cells are dead to prevent the water from being used before it reaches the rest of the plant
• Lignin strengthens the xylem to prevent it from bursting under high water pressure
• Transpiration


  The process of transporting water from the roots to the leaves
• Factors affecting transpiration


  • Temperature
  • Wind
  • Light
• Phloem


  Tubes that transport sugars around the plant
• Translocation


  The process of transporting sugars in the plant
• Stomata


  Tiny holes in the leaf that allow gases and water to move in and out of the plant
• Guard cells


  • Control the size of the stomata by swelling up with water to open them, or losing water to close them
• Leaf structure


  • Waxy cuticle
  • Upper epidermis
  • Palisade cells
  • Spongy mesophyll
  • Lower epidermis with stomata
• Auxins


  Plant hormones that control growth
• Auxins collect on the shady side of shoots


  Shoots grow towards the light (positive phototropism)
• Auxins collect at the bottom of shoots


  Shoots grow against gravity (negative gravitropism)
• Auxins collect on the shady side of roots


  Roots grow away from the light (negative phototropism)
• Auxins collect at the top of roots


  Roots grow with gravity (positive gravitropism)
• Gibberellins


  Plant hormones that control seed germination
• Ethene


  Plant hormone that controls fruit ripening