Plants and Nitrogen
Goals and Objectives:
Be able to describe or illustrate the nitrogen
cycle and define ammonification, nitrification, and denitrification.
Be able to explain why nitrogen fixation is
purely done by prokaryotes.
Be able to describe, in a general sense, the
process of rhizobial infection and nodule formation in legumes.
Be able to describe the biochemical reactions
involved in nitrogen fixation by symbiotic bacteria.
Be able to describe the process of infection
and nodule development by nitrogen fixing bacteria in legumes.
Be able to describe how nitrogen is assimilated
and transported once it has been taken up by the plant in the form of ammonia.
Be able to describe how nitrate is assimilated
Be able to describe how plants cycle nitrogen.
Be able to discuss the importance of nitrogen
in agriculture and in plant communities in general.
Most plants obtain their bulk of their
nitrogen from the soil in the form of _____________ or _______________.
What is the nitrogen cycle? What three
pools of nitrogen make up the nitrogen cycle?
Give a definition for each of the following
and explain where each occurs in the nitrogen cycle.
List the non-biological sources of fixed nitrogen.
What does the textbook mean when it says the
"Biological nitrogen fixation is exclusively a prokaryote domain"
Give a general description of the free-living
nitrogen fixers. (You will not be required to learn the genera).
Give a general description of the nodule forming
symbiotic nitrogen fixers. List the three major genera involved
in this process.
What other symbiotic nitrogen fixers are mentioned
in the text?
Describe the process by which symbiotic nitrogen
fixing bacteria set up infection in legumes.
Write the equation for the enzymatic reaction
involving dinitrogenase. You do not need to know the specifics about
how the enzyme works.
Compare the cost of nitrogen fixation by the
amount of ATP used and the amount of carbon required to fix a gram of dinitrogen.
What does molecular oxygen do to the process
of nitrogen fixation?
List the strategies for regulating oxygen
that have evolved.
Skip sections on Hydrogen Production (pages
108-112) and Genetics of Nitrogen Fixation (pages 112-113).
Once dinitrogen has been fixed by symbiotic
bacteria, how is the ammonia handled within the plant? (See figure 6.12
on page 114)
What are the functions of the following enzymes?
How is nitrogen exported from the nodules?
How do plants that do not form nitrogen-fixing
associations take up nitrogen from the soil?
How are the enzymes involved in nitrate assimilation
As plants age, nitrogen is moved from one
place to another. How is nitrogen usually stored in the plant?
What occurs when a plant is under nitrogen stress (too little nitrogen)?
How are fertilizers used in agricultural situations
and what are the results or effects of this usage?
In natural ecosystems, what controls the availability
of nitrogen to the plant?