Question: Plant competition lab
Objectives
In this lab, we will conduct an experiment to test both
interspe…
Plant competition lab
Objectives
In this lab, we will conduct an experiment to test both
interspecific competition (between radish and collards plants) and
intraspecific competition (radishes competing with radishes, or
collards competing with collards). To determine if competition is
occurring, we will measure survival, plant height, and aboveground
biomass. Once the lab is completed and the data are collated from
the entire class, you will then need to make graphs and answer the
questions at the end of the lab.
Procedure: setup
1. Work in a team with your table.
2. Take 9 pots. Use only pots of the
same shape (square or round); do not mix types.
3. Fill the pots with soil to
within ½ inch of the top.
4. Thoroughly water the soil (until it
runs out the bottom).
5. Add more soil if necessary to bring
up the level to within ½ inch of the top.
6. Place the appropriate number of
seeds on the soil surface. Be sure the seeds are evenly
spaced. In the mixed species pots, intersperse the two
species. See the table below for the nine different treatments.
7. Cover the seeds with a thin layer
of soil. DO NOT water the soil again.
8. Label the pot with your name and
the treatment on a piece of tape. Do not write directly on the
pots
Experimental Design
Single-species treatments (intraspecific competition tests)
4 collard seeds
16 collard seeds
36 collard seeds
4 radish seeds
16 radish seeds
36 radish seedS
Mixed-species treatments (interspecific
competition tests)
2 collard + 2 radish seeds (4
total seeds)
8 collard + 8 radish seeds (16
total seeds)
18 collard + 18 radish seeds (36 total seeds)
Your mixed-species seeds should be arranged in a Latin square
design, as shown below (the immediate neighbors of each seed are
the other species
Procedure: while the experiment
is running (2-3
weeks)
Water the plants regularly (every 2 days) throughout the
experiment.
Procedure: break down experiment
Break down one pot at a time. Before harvesting any plants in a
pot, collect the following data:
Number of surviving radishes
Number of surviving collards
Average height of surviving radishes (cm)
Average height of surviving collards (cm)
2. After counting and measuring
surviving plants, clip each plant where the stem meets the soil.
If your pot is a mixed-species treatment, separate radishes
from collards.
3a. For single-species treatments:
Weigh all plants within a pot for the total aboveground biomass
(g)
Divide the total aboveground biomass by the number of plants
that were alive in the pot, to calculate the mean aboveground
biomass (g per plant)
3b. For mixed-species treatments:
Weigh all the plants of each species separately, for
total aboveground biomass (g) for each species
For each species separately, divide the total
aboveground biomass by the number of plants of that
species that were alive in the pot, to calculate the mean
aboveground biomass (g per plant, within a species)
QUESTIONS:
A. While we didn’t directly measure
this, do you think there was belowground competition occurring
between plants in this experiment? Why or why not?
B. If
there was belowground competition occurring, how would it be
evident? Draw graphs that show your predicted results.
