Plant processes

• Glucose is used for :

  • respiration
  • stored as starch
  • Makes proteins for growth
  • Stored as fats
  • Used for cellulose in plant cell walls
• Limiting factors for photosynthesis :

  • Temperature
  • Light intensity
  • Carbon dioxide concentration
  • amount of chlorophyll
• If you double the distance , light intensity falls by a factor of 4
• Photosynthesis = Carbon dioxide + water — Glucose + oxygen + energy

  ( 6CO2 + 6H2O — C6H12O6 + 6O2 + energy )
• Required practical :

  • Set up equipment as shown
  • Turn lamp on at a measured distance
  • measure volume of bubbles released over a minute
  • Turn off lamp
  • repeat method for a fair test
  • Repeat method at further distances

  
• Plant adaptations for photosynthesis :

  • cells have chloroplasts -green traps light energy
  • Thin , flat leaves - for easy diffusion
  • Large surface area - to catch lots of light
  • have veins - transports water
  • have stomata - let in gas and prevent water loss
• Cell Structure of a leaf :

  1. Cuticle - waxy for waterproofing
  2. Upper epidermis - Transparent to let light in
  3. Air space - efficient diffusion
  4. Spongy mesophyll layer - large SA:Vol allowing lots of gas to enter and exit
  5. Palisade layer - Many chloroplasts
• Transpiration = Movement of water up a plant and its evaporation out of the leaves.
• Translocation = Dissolved sugars moving up and down a plant to the storage tissues .
• Xylem cell adaptations :

  • Made of dead cells - help efficient water transport
  • Thick lignin walls - Very strong
  • Hollow tubes of lumen
• Phloem cell adaptations :

  • Made of living cells - allow cell sap to move from one phloem to another
• Factors that affect transpiration :

  • Temperature - heat. = more energy
  • air movement - wind maintains concentration gradient
  • humidity - more humid = less evaporation
  • light intensity - more light = increased transpiration
• RP effect of light on growth :

  1. set up seedlings in petrified-dish
  2. let seeds germinate on damp cotton wool
  3. make sure each petri-dish has the same number of germinated seedlings
  4. place one petrified-dish in each following location (Windowsill in sunlight , in partial sunlight , in a dark cupboard)
  5. measure growth with a ruler after a week
• Phototropism = a plants response to light controlled by auxin
• Geotropism = a plants response to gravity
• Auxin makes cells elongate (curve) and grow towards or away from light
• Plants hormones uses