PLANT STRUCTURES AND FUNCTIONS

• PHOTOSYNTHESIS =

  • occurs in plants + animals
  • endothermic reaction (takes in more energy than released)
  • light energy transferred to chloroplasts in leaves
• WORD EQUATION FOR P/S

  • carbon dioxide + water --> oxygen + glucose
  • (light over arrow)
• factors affecting p/s

  • light intensity, % amount of CO2/ concentration, temperature
• limiting factors of p/s

  • light intensity, % amount of CO2/ concentration, temperature
• RATE OF P/S PRACTICAL:

  • place pondweed in a test tube of water, seal the top with a bung, capillary tube (also filled with water) leads into a test tube and attaches to a syringe
  • place the lamp at a measured distance from the test tube
  • during p/s oxygen produced, this gas collects in a capillary tube
  • measure the distance the oxygen bubble moved in the tube using a ruler, this = the rate of p/s
• RATE OF P/S PRACTICAL INDEPENDENT VARIABLES:

  • temp - water bath
  • time pondweed left
  • light intensity - distance from light source
• RATE OF P/S PRACTICAL CONTROL VARIABLES:

  • anything affecting p/s that isn't the variable you want to observe
• light intensity is measured in lux
• light intensity = directly proportional to the rate of p/s, because the greater the light intensity the more photons hit the chloroplasts in the leaf and so more p/s occurs
• photons = light energy
• light intensity ∝ 1/distance squared (inverse square law)
• ROOT HAIR CELLS:

  • specialised to take up water via osmosis + mineral ions by active transport from soil
  • found in root tips
  • large surface area - so more water can move in
  • permanent vacuole affects the speed of water movement
  • mitochondria provide energy from respiration and active transport of mineral ions