Transpiration

Cards (25)

  • Define Xylem:
    A non-living plant transport vessel that carries water and dissolved mineral ions from the roots
  • Describe the features of the xylem:
    • long continuous columns - dead cells with open ends
    • Pits (bordered pits) = allows water to move sideways through adjacent vessels, allows water to leave the xylem and pass into the living parts of the plant
    • lignin = thickens the walls, kills the cells, waterproof - withstands the pressure of water, provides strength, prevents collapsing, forms spiral patterns = stretches as the plant grows, allows some flexibility
  • Name the features of the xylem vessels:
    • long continuous columns
    • bordered pits
    • lignin
  • Define Bordered pits:
    Gaps in the cellulose cell wall that form when lignification is not complete which allows water to move sideways through adjacent vessels
  • Xylem vessels are hollow: empty
  • Define Transpiration:
    The loss of water vapour from the plant's stem and leaves via diffusion and evaporation
  • Outline the factors that affect the rate of transpiration:
    • Light intensity
    • Temperature
    • Humidity
    • Air movement
    • Water availability
    • Number of leaves
    • Number/size/position of stomata
    • The presence of a waxy cuticle
  • Outline reasons why transpiration is important:
    • maintains cell turgidity
    • transports mineral ions up the plant
    • cools the surface of the plant
    • supplies water for growth/ cell elongation/ photosynthesis
  • Name the processes taken by water to leave the leaf:
    1. osmosis
    2. evaporation
    3. diffusion
  • What is the equipment used to measure the rate of transpiration?
    Potometer
  • Water molecules are attracted to each other by the forces of cohesion
  • Water molecules are attracted to the sides of the xylem vessels by the forces of adhesion
  • Water molecules have strong cohesive forces thanks to their ability to form hydrogen bonds with one another
  • The narrower the xylem, the bigger the impact of adhesion
  • What aids the movement of water up the xylem against the force of gravity?
    • cohesion
    • adhesion
    • root pressure
  • Water molecules adhere to the walls of the xylem
  • What makes the walls of the xylem narrower?
    • lignin
    • the tension caused by the water molecules being pulled up
  • What causes root pressure?
    the upwards movement of minerals via active transport
  • Formula for volume of cylinders:
    𝚷r2l𝚷r^2l
  • General formula for Rate of Transpiration:
    volume/time
  • The rate of transpiration is the volume of a cylinder divided by the time taken. πr2l/time\pi r^2l / time
    What does r represent?
    the radius of the capillary tube
  • Define Adhesion:
    The attraction of water molecules to the impermeable walls of xylem tissue
  • Adhesion is the formation of hydrogen bonds between carbohydrates in the xylem vessel walls and water molecules
  • Large multicellular animals need a transport system for oxygen and carbon dioxide.
    Large multicellular plants do not need a transport system for oxygen and carbon dioxide, Why?
    Plant cells have a low metabolic rate
  • What waterproof polymer lines the walls of the xylem?
    Lignin