2.3 Plant tissues, organs & systems

Cards (32)

  • Describe the structure of a leaf
    Leaf tissues - epidermis, palisade mesophyll, spongy mesophyll, xylem & phloem
  • How does the structure of epidermal tissue relate to its function?
    Secretes a waxy cuticlewaterproofs leafs surface, reducing water loss (by evaporation)
    Single layer of transparent cellsallow light to pass through
  • How does the structure of palisade mesophyll tissue relate to its function?
    Many chloroplastslots of chlorophyll to maximise light absorption for rapid photosynthesis
  • How does the structure of spongy mesophyll tissue relate to its function?
    Many large air spaceslarge surface area for rapid diffusion of gases eg. CO2
    , O2
  • How does the structure of meristem tissue relate to its function?
    Found in growing tips of shoots and roots
    Made up of stem cellscan differentiate into any type of plant cellallowing plant growth
  • How does the structure of xylem tissue relate to its function?
    Function: transports water and dissolved mineral ions from roots to leaves
    Ligninstrength to withstand pressure of water moving
    Hollow tubes / no cytoplasmwater / mineral ions move easily
    End walls between cells broken downcells form a long tube so
    water / mineral ions flow easily
  • How does the structure of phloem tissue relate to its function?
    Function: transports dissolved sugars (eg. sucrose) from leaves to rest of
    plant for immediate use or storage
  • why is this statement wrong?
    “The waxy cuticle is a tissue / made of cells.”
    It is not made of cells, so is not a tissue. It is made of lipids.
  • why is this statement wrong?
    “Respiration does not happen in plant cells.”
    It happens in cells of all living organisms, to release energy.
  • why is this statement wrong?
    “Xylem only transports water. Ions travel through phloem.”
    Xylem transports water and mineral ions eg. magnesium,
    nitrate. Phloem transports dissolved sugars.
  • Describe why it’s important
    that dissolved sugars are
    moved both upwards and
    downwards in a plant. (3)
    Sugars are made in leaves by photosynthesis
    All cells need sugar for respiration
    Sugars transported to meristems for growth / cell division / mitosis
    OR sugars transported for storage as starch / fat / oil
  • xylem?/phloem comp 6
    Structure
    ● Xylem is made of dead cells and phloem is made of living cells
    ● Phloem cells have pores in their end walls, xylem cells do not
    ● Xylem is hollow / does not contain cytoplasm, phloem does
    ● Xylem contains lignin, phloem does not
    Both tubular and made of cells
    Function
    ● Xylem transports water / mineral ions, phloem transports sugars
    ● Xylem is involved in transpiration, phloem is involved in translocation
    ● Xylem transports unidirectionally, phloem transports bidirectionally
    Both transport liquids / substances throughout the stem / leaves / roots
  • Which organs form the system that transports substances around a plant?
    Roots, stem and leaves.
  • Describe the process of transpiration
    1. Evaporation of water from cells inside leaves
    2. Diffusion of water vapour out of leaves through stomata
  • Describe the transport of water and mineral ions through a plant from the
    soil to the atmosphere, in the transpiration stream
    1. Water evaporates from cells inside leaves and water vapour diffuses out of leaves through stomata
    2. This drives pull of water with dissolved mineral ions up xylem vessels
    3. Water enters through root hair cells by osmosis and mineral ions enter by active transport
  • Describe the role of stomata and guard cells
    Guard cells control size of stomata (pores in epidermis)
    To control gas exchange (CO2
    in / O2 out) and water loss from leaves
    High light intensityguard cells open stomata (as water enters
    guard cells by osmosis so they swell) → allow CO2
    in for photosynthesis
    Hot / dry / low light intensity→ guard cells close stomata (as water
    leaves guard cells by osmosis so they shrink) → prevent water loss
  • explain the effect of increasing this factor on the rate of transpiration
    Factor:Light intensity
    Increasing it... Increases transpiration rate
    Because...
    More stomata open to allow CO2 to enter plant for photosynthesis
    ● So more water vapour can diffuse out of leaves
  • explain the effect of increasing this factor on the rate of transpiration
    factor:Temp
    Increasing it... Increases transpiration rate
    Because...
    Increases evaporation of water (due to increased energy)
  • explain the effect of increasing this factor on the rate of transpiration
    factor: Humidity
    Increasing it... Decreases transpiration rate
    Because...
    Increased water vapour in air
    Reduces concentration gradient (of water vapour) between air and leaf
    ● So diffusion (of water vapour out of leaf) is slower
  • How can the rate of transpiration be estimated?
    Use a potometer to measure uptake of water by a plant
    Assume water uptake is directly related to water
    loss by leaves through transpiration
    Set up according to the diagram
    Measure distance travelled by air bubble in fixed period
    of timecalculate rate of water uptake
  • Describe the process of translocation
    Movement of dissolved sugars (eg. sucrose) through phloem (up and down)
    From leaves (made in photosynthesis) to rest of plant for immediate use (eg. respiration) or storage
  • why is this statement wrong?
    “Transpiration is the same as
    the transpiration stream.”
    Transpiration is the loss of water vapour from leaves. The transpiration
    stream is the constant movement of water through the plant.
  • why is this statement wrong?
    “Leaves lose water by osmosis.”
    Leaves lose water by transpiration.
  • why is this statement wrong?
    “Water vapour enters leaves
    through stomata.”
    Water vapour is lost through stomata during transpiration. Water enters
    plants through roots and is pulled up to leaves through the xylem.
  • why is this statement wrong?
    “Sugar is taken up from the soil
    via roots.”
    Plants make their own sugar by photosynthesis in leaves. This travels to the rest of the plant through phloem in translocation.
  • Explain why a tree might die if the roots of the
    tree are damaged. (6)
    - Less absorption of water
    Lower rate of photosynthesis so less glucose
    So less respiration / cellulose made for cell walls /
    amino acids made for making new proteins
    - Less absorption of ions
    Fewer nitrates so fewer proteins made for growth
    Fewer magnesium ions so less chlorophyll
    produced so lower rate of photosynthesis
    - Damage to phloem
    Less transport of sugars to root cells
    For respiration
    - Damage to xylem
    Less water transported
    Fewer nitrates reach cells so fewer proteins made
    Less anchorage
  • Describe two differences between the
    transpiration stream and translocation. (2)
    Transpiration stream involves xylem, translocation
    involves phloem
    Transpiration stream transports water (& mineral
    ions), translocation transports dissolved sugars
    Transpiration stream moves substances upwards,
    translocation moves substances up and down
  • A teacher used celery to show water uptake in
    plants. Celery was left in water with red dye for 3
    hours. After, the leaves of the celery were dark
    red. Explain how. (3)
    Water / dye moves up plant / stem / celery
    In the xylem
    To the leaf / stomata
  • Having a large number of stomata per mm2 of
    leaf surface can be a disadvantage to a plant. (1)
    More water loss (plant more likely to wilt)
  • Rate of water loss from leaves at midnight is
    much lower than at midday. Explain why. (2)
    Stomata are (almost completely) closed (at night)
    Because it’s cooler / no light
  • Most plants have more stomata on the lower
    surface of a leaf than on the upper surface.
    Explain why. (3)
    Cooler around lower surface
    More humid around lower surface
    ● So less water evaporated
  • A student used a potometer to investigate the
    rate of water uptake in a plant shoot. Explain why
    the air bubble would not move if the
    investigations were done in the dark. (3)
    No photosynthesis
    ● So stomata closed (as no CO2 needed)
    ● So no transpiration