Roots, Soils, and Nutrient Uptake

Goals and Objectives:

  1. Be able to give a general description of soil make up and how soil chemistry affects mineral uptake by a plant root.
  2. Be able to describe and give an example of each of the membrane transport mechanisms used to move ions across membranes in a plant.
  3. Be able to describe the four ways that ions can be transported across a plant cell membrane with the aid of an ATPase-proton pump.
  4. Be able to describe how ions pass into a plant root.  Be sure to mention the apparent free space movement and the importance of the Casparian strip.
  5. Be able to describe the importance of root-microbe interactions in the up-take of mineral ions.

Study Questions:


  1. How do soil colloids affect the availability of cations to the plant?
  2. What is a lyotropic series?  What is the lyotropic series for cations in soils?
  3. What is ion exchange?  How do plants handle ion exchange with soil particles?
Membrane Transport:
  1. What controls simple diffusion?  What solutes of biological importance move by simple diffusion in a plant?
  2. What is facilitated diffusion?
  3. What is the difference between carrier proteins and channel proteins?
  4. What are gated channels?
  5. What ions move by channels?
  6. What is active transport?  What is the relationship between active transport and "pumps"?
  7. Look at Table 5.1.  How could you use the concepts of ion selectivity and ion accumulation to interpret this data ?
  8. How do the charges on ions lead to electrochemical gradients across cell membranes?  How do these electrochemical gradients lead to transmembrane potentials?
  9. Describe how ATPase-proton pumps aid active transport of ions.
  10. What is a proton motive force?
  11. Compare uniport, antiport, and symport.  Give examples of each of these mechanisms for transport of ions.
  12. What are aquaporins
Ion Uptake by Roots
  1. Look at the graph on page 89 (Figure 5.10).  Explain what is occurring in the tissues of the plant.  Be sure to mention the apparent free space accumulation of ions.
  2. How would the graph on page 89 (Figure 5.10) change if the roots were placed in an ion exchange medium?
  3. What constitutes the apparent free space?
  4. What role does the Casparian stripe (band) play in the apparent free space of a root?
  5. Describe how ions move through roots to the stele.
Root-Microbe Interactions
  1. How do root secretions affect the environment around the growing root?
  2. What are proteoid roots?
  3. What are mycorrhiza?
  4. What are the two types of mycorrhiza?
  5. What is the physiological role of mycorrhizae?