Chapter 7: Transportation in Plants

Image from Untamed Science

7.1 Structure of transport tissues

a) 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 (see 1.1c: use an eyepiece graticule and stage micrometer scale to measure cells and be familiar with units (millimetre, micrometre, nanometre) used in cell studies)



b) 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

c) 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



d) Relate the structure of xylem vessel elements, phloem sieve tube elements and companion cells to their functions



.: sub-topical summary: anatomy + cells function + practical stuff


7.2 Transport mechanisms

a) Explain the movement of water between plant cells, and between them and their environment, in terms of water potential (see 4.2. No calculations involving water potential will be set)



b) Explain how hydrogen bonding of water molecules is involved with movement in the xylem by cohesion-tension in transpiration pull and adhesion to cell walls



c) Describe the pathways and explain the mechanisms by which water and mineral ions are transported from soil to xylem and from roots to leaves (include reference to the symplastic pathway, apoplastic pathway and Casparian strip)



d) Define the term transpiration and explain that it is an inevitable consequence of gas exchange in plants



e) Investigate experimentally and explain the factors that affect transpiration rate using simple potometers, leaf impressions, epidermal peels and grids for determining surface area



f) Make annotated drawings, using prepared slides of cross-sections, to show how leaves of xerophytic plants are adapted to reduce water loss by transpiration



g) 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


h) 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



i) Explain mass flow in phloem sap down a hydrostatic pressure gradient from source to sink



.: sub-topical summary: how water moves in plants + what is transpiration + factors that affect transpiration + adaptation of xerophytes + how assimilates move


Overall summary:
- Anatomy of the transport system in plant
- Cellular functions
- Movement of water
- Transpiration
- Xerophytes
- Movement of 'foods'