Lab: Propagating Green Onions
Background Information:
* Green onions (Allium fistulosum) also known as scallions, are close relatives being garlic, shallots, chives and leeks.
* Green onions have hollow, tubular green leaves growing directly from a bulb. The “bulb” is actually the stem!
* Green onions are known for their ability to regrow after being cut. As long as a cutting includes meristem tissue, the cutting can grow into a whole new plant! In this lab we will be testing the ability of green onion plants to regrow from cuttings of various lengths.
Background: answer the following questions in your lab book.
1. What is a plant meristem? Where are plant meristems located?
2. Where are stem cells located in a plant?
3. List two characteristics of plant stem cells.
4. Explain how a whole new plant can be grown (with all it’s different parts each with a different function) from a small cutting.
Problem Question: (copy this down)
Does the distance a cutting is made from the root base affect the amount of growth that occurs in Allium fistulosum?
Hypothesis:
Write a hypothesis for the problem question. Do you think how far away from the root you cut will affect how much the plant grows afterwards? Why or why not?
Setup Procedure: (you do not need to copy the procedure)
1. Get 5 green onions (A. fistulosum) from your teacher.
2. Place the 5 onions on a paper towel and number each #1-5. Write the # on the paper towel under the onion.
3. Measure the length of the 3 longest roots in centimeters (to the hundredths place). Record the data in a table. Calculate the mean of the 3 root lengths and record in the data table. See the data collection table below.
4. For each onion, locate where the roots meet the stem. For green onion #1, cut 1cm from where the roots begin. For onion #2, cut 2 cm from the roots begin. Continue, until by onion #5 you are cutting 5 cm from where the root begins.
5. Note any observations you make about the green onions. Are they healthy? Fresh? Browning? See the data collection table below.
6. Push a toothpick through the green onion segment, placing the toothpick as close as possible to the base of the stem.
7. Label 5 test tubes, #1-#5. Fill each tube to the rim with distilled water. Submerge each onion to their respectively numbered test tube.
8. Have each group member write their name on a notecard and then attach it with tape to the test tube rack. Place the 5 tubes in your test tube rack and place them under a grow light. Place your rack in the tray labeled with your period. Wait 1-2 weeks, filling the tube with water as needed.
Initial Data Collection: Make a table in your lab book like the one below:
Give the data table an appropriate title.
Green Onion #
Root 1 Length
(cm +/- 0.05)
Root 2 Length
(cm +/- 0.05)
Root 3 Length
(cm +/- 0.05)
Mean Root Length
(cm)
Stem Length of Onion (cm)
Observations
#1
1.0
#2
2.0
#3
3.0
#4
4.0
#5
5.0
Post Growth Procedure: (you do not need to copy the procedure)
1. Remove the roots from the water and dab dry.
2. For each onion, measure the length of the 3 longest roots in centimeters (to the hundredths place). Calculate the mean of these 3 lengths and record in a data table.
3. For each onion, measure the length of the longest leaf in cm from the cut site and record in the data table.
4. Record any qualitative observations of note for each green onion.
5. 1 member of your group needs to submit data here.
Final Data Collection: Make a table in your lab book like the one below:
Give the data table an appropriate title.
Cut Stem Length of Onion (cm)
Root 1 Length
(cm +/- 0.05)
Root 2 Length
(cm +/- 0.05)
Root 3 Length
(cm +/- 0.05)
Mean Root Length
(cm)
Longest Leaf Length of Onion (cm)
Observations
1.0
2.0
3.0
4.0
5.0
________________
Data Analysis:
Class Data: (you do not need to copy the class data)
Mean Root Lengths of Green Onions Cut to Various Sizes
Cut Stem Length of Onion (cm)
INITIAL
Length (cm)
FINAL
Length (cm)
CHANGE
in Length (cm)
1.0
2.1
3.7
1.6
2.0
2.2
3.9
1.7
3.0
2.1
4.0
2.0
4.0
1.7
4.0
2.3
5.0
1.9
4.4
2.5
Mean Leaf Lengths after 5-6 days of Growth of Green Onions Cut to Various Sizes
Cut Stem Length of Onion (cm)
Final Mean
Longest Leaf Length (cm)
Standard Deviation (cm)
1.0
1.4
1.8
2.0
2.6
1.8
3.0
4.1
2.4
4.0
5.1
3.2
5.0
7.1
3.5
Graphing:
Create two graphs, being sure to follow the graphing checklist.
1. Graph the mean change in root length for the five cut stem lengths of the onion.
2. Graph the mean longest leaf length after growth for the five cut stem lengths of the onion.
(If you don’t understand how to put SD error bars on the graph, we will cover that in class on Monday.)
Analysis Questions:
1. Propose an explanation for the root growth results. In other words, what is the biological reason why the roots did not show different growth between the different cut heights.
2. Propose an explanation for the leaf growth results. In other words, what is the biological reason why some onions grew longer leaves than others.
3. What parts of the onion would NOT be able to regenerate a new plant? Why not?
4. List two possible applications of plant propagation.
5. List three possible modifications of this experiment that would test different variables.