Leafs and plants

• CO2 is needed for photosynthesis
• Gases move in and out via diffusion
• Plants produce CO2 via respiration
• Photosynthesis only occurs in chloroplasts at certain times in the day
• respiration occurs in the mitochondria at all times of the day
• plants drop their leaves when respiration produces more energy than photosynthesis
• Xylem is responsible for transpiration and transports water from the roots to the leaves- uni directional
• Phloem transports glucose and amino acids from roots to leaves and leaves to roots- bi directional
• leaves are thin to decrease diffusion distance, have airspace to increase diffusion speed and have a stomata for constant gas exchange
• Stomata are holes on the underside of the leaf. They are surrounded by two guard cells that control when they are open and closed
• When CO2 is low, K+ ions are pumped into guard cells from epithelial cells, decreases water potential, water moves into the guard cells causing them to be turgid and open the stoma
• When CO2 is high, K+ ions move out, increased water potential, water moves out via osmosis, guard cells become placid, stoma closes
• plants can conserve water and reduce water loss by reducing their surface area (having thin pointy leaves)
• xerophytic plants don't want to loose water, adaptions:

  • thick, leathery skin
  • hairy surfaces
  • reduced leaf size
  • rolled leaves
  • reduced density of stomata