Plant stems

• What are vascular bundles?

  Xylem and phloem vessels in plants
• What is the sclerenchyma?

  Contains lignin and provides stability to vascular bundles

  • mainly found around vascular bundles- the older the bundle, the more sclerenchyma fibres surrounding it
• What makes something a good energy store?

  • branched- can be rapidly hydrolysed to release glucose for respiration
  • compact- more energy can be stored in a small space
  • insoluble- doesn't affect the osmotic properties of a cell
• Method to find the relationship between actual diameter and the tensile strength of fibres

  1. Extract individual fibres from plant
  2. Measure the diamter by microscopy
  3. CONTROL variable- same fibre length/ carry out experiment at the same temperature under the same humidity
  4. Clamp the fibre and add hanging masses at regular intervals until the fibre breaks.
  5. REPEAT to find the mean
  6. Divide force by cross-sectional area
• How do you calculate tensile strength?

  Force divided by cross-sectional area.

  • mention that they need to calculate the cross sectional area
• What is the function of a granum in photosynthesis?

  Granum is formed from multiple layers of the thykaloid to increase the surface area for light absorption.

  • thykaloid membranes have chlorophyll which absorbs light.
  • electron carrier molecules in thykaloid are involved in ATP production