Epsilon (AS) Biology | Transport in plants | Lesson plan

Schedule

Jan 18 - Jan 31 ( 2 weeks)

Content

  • Why transport?
  • Xylem and phloem
  • Transport of water
  • Transport of minerals
  • Transport of manufactured food.
  • Sieve tubes vs Xylem vessels

Instructional objectives

  • draw and label from prepared slides plan diagrams of transverse sections of stems, roots and leaves of herbaceous dicotyledonous plants using an eyepiece graticule to show tissues in correct proportions
  • draw and label from prepared slides the cells in the different tissues in roots, stems and leaves of herbaceous dicotyledonous plants using transverse and longitudinal sections
  • draw and label from prepared slides the structure of xylem vessel elements, phloem sieve tube elements and companion cells and be able to recognise these using the light microscope
  • relate the structure of xylem vessel elements, phloem sieve tube elements and companion cells to their functions
  • explain the movement of water between plant cells, and between them and their environment, in terms of water potential
  • explain how hydrogen bonding of water molecules is involved with movement in the xylem by cohesion-tension in transpiration pull and adhesion to cellulose cell walls
  • describe the pathways and explain the mechanisms by which water and mineral ions are transported from soil to xylem and from roots to leaves (symplastic pathway and apoplastic pathway and Casparian strip)
  • define the term transpiration and explain that it is an inevitable consequence of gas exchange in plants
  • investigate experimentally and explain the factors that affect transpiration rate using simple potometers, leaf impressions, epidermal peels, and grids for determining surface area
  • make annotated drawings, using prepared slides of cross-sections, to show how leaves of xerophytic plants are adapted to reduce water loss by transpiration
  • state that assimilates, such as sucrose and amino acids, move between sources (e.g. leaves and storage organs) and sinks (e.g. buds, flowers, fruits, roots and storage organs) in phloem sieve tubes
  • explain how sucrose is loaded into phloem sieve tubes by companion cells using proton pumping and the co-transporter mechanism in their cell surface membranes
  • explain mass flow in phloem sap down a hydrostatic pressure gradient from source to sink

Teaching Process

  • Importance of transport systems in general is first discussed.
  • Plant tissue cross sections are studied to understand the structure
  • Activities centered around transpiration rate would be used as a basis for discussing about transport of water and minerals
  • Discussion on mechanisms of active transportation through phloem
  • A revisit on the structure linking it with the functions

Activities

  • Looking at prepared slides of plants to identify tissues and draw a plan-diagram.
  • Making a simple potometer
  • Using the potometer to study the effect of different conditions on transpiration rate
  • Making leaf impressions in nail polish to measure stomatal density and comparing the upper and lower surface of leaves, as well as across plants

Suggested reading / References

Assignments / Evaluation

  • written test
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