Cpac 4

• Pollen tube


  A path digested through the stigma of a plant by hydrolytic enzymes so the pollen grain can travel down the stigma and through the micropyle to the embryo sac and eventually to the ovum for fertilisation
• Pollen tube nucleus


  Catalyses the production of hydrolytic enzymes
• Equipment


  • 2M sucrose solution
  • Mineral salt culture medium
  • Optical microscope
  • Filter paper
  • Stage micrometer
  • Flowering plants
  • Petri dishes
  • Distilled water
  • Measuring cylinder
  • Stop clock
  • Balance
  • Scissors
  • Forceps
  • Mounted needle
  • Pipette
• Method


  1. Dilute the stock sucrose solution to several set concentrations

  2. Place a moist piece of filter paper into a petri dish to form a humid chamber

  3. Put a few drops of sucrose solution and an equal volume of mineral salt medium onto a clean microscope slide

  4. Use a mounted needle to rub the anther of the flowers so they shed some pollen onto the microscope slide

  5. Place the slides into the petri dish until it is time to observe them

  6. Start the stop clock. Place the slides under the microscope and use a calibrated eyepiece graticule to measure pollen tube growth
• Hazards


  • Biohazard
  • Cuts from sharp object
  • Scalpel
• Biohazard


  Allergies; soil bacteria; contamination
• Cuts from sharp object

  Take care when handling glass objects; keep away from edge of desk
• Scalpel


  Cuts from sharp object
• Safety precautions


  1. Wash hands after practical

  2. Elevate cuts; apply pressure; do not remove glass from wound; seek medical assistance

  3. Cut away from fingers;use forceps to hold sample whilst cutting
• As sucrose concentration increases


  Mean pollen tube growth also increases up to an optimum
• After the optimum sucrose concentration

  Mean pollen tube growth decreases as sucrose concentration increases
• Osmotic effects


  Cause the relationship between sucrose concentration and pollen tube growth
• Graph


  Plot a graph of the sucrose concentration against pollen tube growth