Plants, like animals, have a way to reproduce and make new baby plants. Unlike most animals, plants commonly use two different ways to make new plants. A plant will use one process or the other, depending upon the environmental conditions at the time of reproduction. These two different types of reproduction are called sexual reproduction and asexual reproduction.
Sexual reproduction in plants is when a plant makes a seed. The seed contains the embryo, or baby plant, that will grow into a mature plant under the right conditions. Sexual reproduction requires both male and female parts of a plant, which mix together to form the embryo. Because male and female parts both contribute to the new plant it is unique from both of the parents, so sexually reproduced plants are very diverse.
Asexual reproduction in plants is when a plant makes a new plant without making a seed. During asexual reproduction, male and female parts do not mix to make a new plant. Instead, the new plant is a clone of the parent plant and is an exact copy of the parent. Because of this, asexually reproduced plants are not diverse.
Even though asexual reproduction produces plants with very low diversity it has many useful applications. Cloning plants is very common in agriculture because of the speed with which a plant can be made. It also allows a farmer to grow reliable produce by limiting the variation of the plant.
In this experiment, you will investigate how plants produce asexually by making clones of a cabbage plant. Which parts of the cabbage do the clones come from? Under what conditions do plants produce clones most reliably? How long do plants need to grow clones? Do the clones look like the parent plant?
Terms, Concepts and Questions to Start Background Research
To do this project, you should do research that enables you to understand the following terms and concepts:
* sexual reproduction
* asexual reproduction
* How are plants cloned?
* What are the best conditions for cloning a plant?
* Which parts of the plant can be used to make a clone?
* How does plant cloning benefit modern agriculture?
Materials and Equipment
* a head of cabbage from the grocery store
* small Zip-Lock baggies
* water mister or sprayer
* cookie sheet or large tray
* permanent marker
* different kinds of materials for growing the clones:
o moist paper towels
o peat moss
o wood mulch
o shredded paper
o dead leaves (tend to be acidic)
o grass clippings (rich in nitrogen)
o fertilizer pellets (also rich in nitrogen)
o brown paper lunch bag (to grow in the dark)
o rotting fruit or vegetables (release ethylene gas)
1. Buy a head of cabbage from the grocery store. A long cabbage (like a Napa cabbage) is easier to use than the more common round cabbage because it is less dense, easier to pick apart, and has a longer stem. The number of conditions you can test will depend upon the length of the stem, so if you want to test many conditions pick as long a cabbage as you can find.
2. Beginning with the outer leaves, pull all of the leaves of your cabbage off of the stem. Don't worry if you don't get the entire leaf removed, it is better to leave some of the leaf attached than to risk damage to the stem. You might like to use the leaves to make a yummy cabbage soup or coble-slaw!
3. With your parents help, use a knife to slice the stem cross-wise into 1-inch long pieces. You will use one piece for each condition you will test.
4. Put one piece of the cabbage stem into each baggies.
5. Fill each baggie half-full with the material you would like to test. For example, if you want to test wood mulch, add wood mulch to one of the baggies with a piece of cabbage until it is about half way full.
6. Using the water mister, spray the material in the baggies 3–4 times until the material is moist, but not wet.
7. Seal the baggies and place the baggies on the cookie sheet or tray.
8. Use a permanent marker to write the type of condition on the outside of the baggies. This will be important later when you empty the contents out of each bag to examine your cabbage pieces.
9. Repeat steps 5–8 with each material and condition you are testing.
10. Place the tray near a window and leave at room temperature. If the bags are properly sealed, you should not need to add water during this time. You may notice that water begins to condense and form droplets inside the bags, this is normal.
11. After one week, open the bags one at a time to look at the cabbage stem.
12. Use a notebook to write down observations and make drawings of each cabbage stem. For each condition use a new page. Write the date and condition at the top of the page, followed by a written description and drawing. These will be your records to use later when analyzing your experiment.
13. After examining each stem place it in the baggies, lightly mist and seal the baggie. You will leave the tray out for another week before making more observations.
14. How do the stems continue to change? Do you see new baby cabbages forming? Where on the stem do the clones come from?
15. After making observations for a few weeks, count the number of clones formed in each experiment.
16. Make a bar graph of your results, clearly labellings each condition on your graph. The height of each bar will be the number of clones grown on the stem for that type of condition. You should have the same number of bars on your graph as you have baggies.
17. Which conditions made the best clones? Which conditions did not make any clones?
* Different conditions for cloning can have short term and long term effects. Conditions that appear to be good in the beginning, may not yield a healthy, mature crop. Now that you know some conditions for starting your clones, you can test these conditions on the yield of a healthy mature crop. You can test this by transplanting your clones into the garden. First, cut the stem apart, separating each clone from the rest of the stem. Plant each clone in a shallow depression and cover with soil. Use Popsicle sticks to label each row of clones for each different condition. Which clones grow the best mature plants? Which conditions are best for long term crop yield?
* You can clone other crops as well. Do other crops need the same conditions to be cloned? Do the clones come from the same part of the plant? Try using parts of the celery stem, tubers of potatoes, slices of carrot, lettuce stems, separated garlic cloves, etc...
* Cloning is important for agriculture because it increases the speed of crop production and the yield of crops. How much faster is cloning a vegetable than growing it from seed? Try an experiment comparing the time it takes to produce a mature lettuce or cabbage by cloning and by growing from seed. How much faster is it? What is the yield from each method?
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