Roots, Soils, and
Nutrient Uptake
Goals and Objectives:
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Be able to give a general description of soil
make up and how soil chemistry affects mineral uptake by a plant root.
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Be able to describe and give an example of
each of the membrane transport mechanisms used to move ions across membranes
in a plant.
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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.
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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.
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Be able to describe the importance of root-microbe
interactions in the up-take of mineral ions.
Study Questions:
Soils:
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How do soil colloids affect the availability
of cations to the plant?
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What is a lyotropic series? What is
the lyotropic series for cations in soils?
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What is ion exchange? How do plants
handle ion exchange with soil particles?
Membrane Transport:
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What controls simple diffusion? What
solutes of biological importance move by simple diffusion in a plant?
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What is facilitated diffusion?
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What is the difference between carrier proteins
and channel proteins?
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What are gated channels?
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What ions move by channels?
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What is active transport? What is the
relationship between active transport and "pumps"?
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Look at Table 5.1. How could you use
the concepts of ion selectivity and ion accumulation to interpret this
data ?
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How do the charges on ions lead to electrochemical
gradients across cell membranes? How do these electrochemical gradients
lead to transmembrane potentials?
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Describe how ATPase-proton pumps aid active
transport of ions.
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What is a proton motive force?
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Compare uniport, antiport, and symport.
Give examples of each of these mechanisms for transport of ions.
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What are aquaporins
Ion Uptake by Roots
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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.
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How would the graph on page 89 (Figure 5.10)
change if the roots were placed in an ion exchange medium?
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What constitutes the apparent free space?
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What role does the Casparian stripe (band)
play in the apparent free space of a root?
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Describe how ions move through roots to the
stele.
Root-Microbe Interactions
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How do root secretions affect the environment
around the growing root?
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What are proteoid roots?
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What are mycorrhiza?
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What are the two types of mycorrhiza?
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What is the physiological role of mycorrhizae?