ATS GCSE Biology - Transpiration & translocation

• rate of transpiration

  1/time

  
• potometer


  apparatus used to measure the rate of transpirationmost water loss is through transpiration, but a small amount is used in metabolism, in photosynthesis

  
• all stomata close

  when water is lost faster than taken in by the rootsphotosynthesis stops and the the plant may overheat but this prevents most water loss and prevents further wilting
• wilting


  when water is lost faster than taken in by the rootsis a protection measure against further water loss the leaves collapse and hang down reducing the surface area for water to evaporate from
• most stomata

  are found on the underside of the leaves protecting them from the direct light energy of the Sun

  
• the cuticle


  waxy and waterproof layer to prevent uncontrolled water lossin hot environments this is very thick and shiny

  
• coloured dye


  plants placed in coloured dye show the movement of water and mineral ions through the xylem

  
• sugars transported

  to growing areas of the stems and rootsused to make new plant cells

  
• translocation

  movement of SUGARS from leaves to the rest of the plant up and down the phloem

  
• increased temperature

  molecules move faster so diffusion occurs fastermore stomata are open for gas exchange with increased rate of photosynthesis

  
• wind


  increases evaporation and also maintains a steep concentration gradient

  
• steeper concentration gradient

  water vapour diffuses faster into dry air than humid airwindy conditions removes water vapour away from the leaf

  
• increases the rate of transpiration

  hot, dry, windy conditionsincreased light intensityincreasing rate of photosynthesis or evaporation

  
• different conditions affect the rate of transpiration

  temperaturehumidity air movementlight intensity

  
• diffusion


  of water, carbon dioxide and oxygen through the stoma

  
• evaporation


  from the surface of the cells

  
• plant transport systems


  transpiration and translocation

  
• transpiration stream


  constant movement of water molecules through the xylem from the roots to the leaves

  
• loss of evaporated water


  pulls up more water through the xylem to take its place

  
• transpiration

  evaporation of WATER vapour from leaves through stomata