plant structure

• Carbon dioxide + water = glucose + oxygen
• happens in the leaves

  • chloroplasts
  • chlorophyll
• carbon dioxide obtained

  • from the air
  • through stomata
• water obtained

  • from the soil
  • by root hair cells
• photosynthesis - endothermic

  • requires energy from the sun
• uses for glucose

  • make cellulose
  • respiration
  • make amino acids
• factors effecting photosynthesis

  • temperature
  • light intensity
  • carbon dioxide concentration
• temperature

  • TOO COLD - enzyme cannot work properly - decreases the rate
  • TOO HOT - enzyme denatures so active site changes shape and substrate can no longer fit
• transpiration - loss of water from leaves by evaporation
• cross section of a leaf

  • waxy cuticle
  • upper epidermis
  • cell wall / pallisade cells
  • cytoplasm
  • air spaces
  • lower epidermis
  • stomata
• at night - guard cells shrink and stomata closes so no gasses or water escape or enter
• during the day - guard cells are swollen so stomata opens for gasses and water to enter / leave
• xylem

  • transports water and mineral ions
  • from the roots to the leaves
  • during transpiration
• xylem - long , hollow cells with lignin made from dead cells
• phloem

  • transports sucrose and amino acids
  • between leaves and other parts of plant
  • during translocation
• phloem - tubes of living cells called sieve tubes / have companion cells which provide energy
• translocation - movement of dissolved food substances around the plant
• leaf adaptations

  • large surface area - absorb more sunlight
  • thin - gasses can easily diffuse
  • stomata - gas exchange
• xerophytes - adapted to live in dry conditions
• plant hormones - auxins
• tropism - response to stimulus
• phototropism - response cause by light
• gravitropism - response cause by gravity
• light from above

  • auxins evenly distribute at the tip
  • cells elongate at the same rate
  • grow straight up
• light from one side

  • auxins move to the shaded side
  • shaded side cells elongate faster
  • shoot bends toward the light
• gibberellin - plants hormones used to promote germination , flowering and fruit formation
• ethene - plant hormone which ripens fruit
• inverse square law = 1 / (distance) squared
• experiment to test the effect of light intensity on photosynthesis

  • put some pond weed in a test tube with water
  • put the test tube in a beaker of water ( heat shield)
  • put the beaker 20 cm away from the light
  • turn on the light
  • count the number of bubbles produced
  • move the beaker away (30 cm , 40 cm )
  • repeat process
  • compare results
  • the more bubbles - the faster the rate of photosynthesis