NITROGEN FIXATION LAB
WARNING: DO NOT
BEGIN ANY LAB
WORK UNTIL YOU
HAVE READ AND
ANSWERED THE PRE
LAB QUESTIONS AND
I HAVE CHECKED
YOUR ANSWERS
Plants need
nitrate
(NO3) to
create the
amino acids
that they
need to
grow.
Unfortunatel
y Nitrate is
not always
available so
it must be
created
using
nitrogen gas
(N2) from
the
atmosphere.
The process
of
converting
N2 to NO3 is
called
nitrogen
fixation.
Nitrogen
fixation
occurs when
specialized
bacteria
attach
themselves
to the roots
of plants.
The bacteria
form a
symbiotic
relationship
with the
plants. The
plants give
the bacteria
sugars
which the
bacteria
need for
food, while
the bacteria
make
nitrates for
the plants.
There is
however
one
problem.
Only certain
types of
plants called
legumes can
form a
relationship
with the
bacteria.
Beans are
legumes
while
radishes are
not.
In this lab,
you will
determine
how the
presence of
a nitrogen
fixing
bacteria
called
Rhizobium
effects the
level of
nitrogen
found in
radish and
bean plants.
You will
also
determine
how the
presence of
bacteria
effects plant
growth.
PRE LAB QUESTIONS ( answer these questions on your individual lab sheet)
1. How will the presence of Rhizobium affect the amount of nitrate in your group's
radishes? Explain in detail why?
2. How will the presence of Rhizobium affect the amount of nitrate in your group's
beans? Explain in detail why?
3. Out of all four plants which one should have grown the most? Explain why you
chose your answer in detail?
4. What is nitrogen Fixation? DETAILS
5. What are the independent and dependent variables in this experiment?
6. How will you measure and compare the growth of your plants?
Add the following tables to your sheet to keep track of your results
BEANS
Test
Rhizobium Sample
Control Sample
Plant Growth
Nitrogen Content mg/L
RADI
SHES
Measuring Nitrates
In order to measure the
amount of nitrate in your
plant roots you will need
to use the nitrates
chemical test kit. Follow
the procedure below for
each of the 4 plant
samples. Remember to
fully clean your materials
and your hands between
samples or you will
contaminate your results.
You should work on more
then 1 sample at a time.
Step 1 - After removing
your plants from their
containers and removing
the dirt, cut off a small (
1cm) section of the plants
root
Step 2 - Obtain a small
beaker of distilled water
and a pipette from
the side of the room. Fill a
small test cylinder to the
3mL line with the
distilled water (it is the
2nd small line from the
bottom)
Step 3 - Obtain the Nitrate
Test Solution #1 bottle
from the kit and use it to
fill the test cylinder the
rest of the way up to the 5
mL mark. Place your
root section into the
container, cap, and shake
vigorously for 1 minute.
Step 4 - Remove the cap
from the cylinder and add
2 spatulas full of the
Nitrate
Indicating powder #2.
Recap and shake
vigorously for 1 minute.
Place the
cylinder aside and wait at
least 10 minutes before
reading.
Measuring Plant
Growth
You will determine your
own method for
measuring plant growth.
Options
include measuring total
height, total mass, number
of leaves, size of
leaves etc. Make sure you
select the most successful
plant in each container
before you compare them.
Clean UP
Before moving on, make
sure all dirt goes in the
container, all materials get
put back and you clean
your desk surface and if
needed the floor. This can
cost you points.
POST LAB QUESTIONS( answer these questions on your individual lab sheet)
1. Do your experimental results match your prediction from PRE LAB Question
#1? If not, explain at least two possible errors in your experiment.
2. Do your experimental results match your prediction from PRE LAB Question
#2? If not, explain at least two possible errors in your experiment.
3. Do your experimental results match your prediction from PRE LAB Question
#3? If not, explain at least two possible errors in your experiment.
4. What did you learn from this experiment?