Burhan Riaz Spruce Creek High SchoolIB Biology HL/Period 3 Planning Date: 10/03/08 Richard Snodgrass Execution Date: 10/06/08

The Effect of Depth on Onion Seed Germination

Introduction:

Germination, or the sprouting of a seedling, is affected by a variety of factors and

these factors are important to understand especially to the farming industries (Habdas).

Discovering the factors of germination and their rates of change can predict the future

and help us understand historical events such as the Dust Bowl Era, which could have

been prevented if factors such as sowing depths or temperature were fully understood

(Habdas). There are numerous contributors to germination but the biggest include

temperature, water, oxygen, light intensity, and seed depth (Sell). All of the major factors

will affect this experiment.

For this particular experiment, the sowing depth of the Allium cepa (the common

onion) seed will be the determining factor of germination. Generally, the Lilliaceae’s

optimum germination rate occurs between .5 to 1 inches of depth of planting (Kennell).

With proper watering and environmental factors, germination should quickly occur from

the .5 to 1 inch sowing depth in the onion plant at 75 C, which is the optimum

germination temperature for the onion plant (Kennell). The onion seed does not need

much water or time to start germinating. In fact, it should only take from a minimum of 7

days to a maximum of 14 days to germinate (Sell). It can be assumed that an onion seed

that hasn’t germinated for more than two weeks, failed to start the germination process.

Of course, the time of germination varies from other factors such as how close onion

plants are planted near each other (Sell). This will definitely be a limiting factor since the

experiment will take place in small sections of a large container.

Problem:

Do different sowing depths affect the time of germination in the common onion?

Hypothesis:

If onion seeds were planted at varying depths, then the time of germination should vary

accordingly. Seeds will probably not germinate below 1.5 inches of the soil and above .5

inches of the soil. Usually, seedlings have a certain amount of time after they break their

shells and until they can start making their own energy by photosynthesis, which occurs

when the plant sprouts. The survival of the seedling is based upon the need to

photosynthesize and the lower the seed is planted, the less chance it has to achieve

germination.

Independent Variable:

Depth (inches)

Dependent Variable:

Time of Germination (days)

Controlled Variables:

Light Intensity: The onion plant is placed under a dim light at all times so when

the seeding continues to grow after it sprouts and it is easy to document the date

of germination.

Water: It is necessary to water each seed the same amount of water so that the

chance of germination is only affected by depth.

Temperature: This is a large determining factor of germination and can greatly

affect the rate of germination over time. Optimum temperature is 75.

Sowing distance: It is important to keep an equal amount of distance between the

onion seeds since they all use nutrients from the soil and can limit other seeds in

the vicinity.

Type of Seed: Different onion seeds will most likely be affected by factors at

various rates and therefore is important to use a particular type. Allium cepa will

be used.

Type of Soil: Different companies often use different chemicals and fertilizers

when preparing soil. To have a fair experiment, the soil will be used from the

same bag.

Materials:

Allium cepa (x75) - The seed that will be used throughout the experiment.

Soil – Used as a moist environment for the seed. Also supplies nutrients.

Florescent Lights – The best type of indoor light for the plant.

Water – Is needed to break the shell of the seed and to supply it for the growth

phase.

Container – Holds all the soil and seed. There should be 15 sections for this

experiment.

Ruler – Measures the depth the seed is measured at.

Post-it Notes – Labels the depths of the individual sections of the container.

Procedure for Controlled Variables:

Light intensity – The same florescent light bulbs will be used throughout the

experiment.

Water – 20 ml will be given to each section of the container every day during the

experiment.

Temperature – Optimum temperature is 75 C, so room temperature is sufficient

for the experiment.

Sowing distance – 5 seeds need to be sowed in each section. 4 will go to the

corners and 1 will be placed in the middle. This way the seeds will be equally

distanced.

Type of Seed - Plant the same type of seed by using one bag of Allium cepa.

Type of Soil – Use soil from the same bag.

Procedure for Data Collection:

In the container, there should be 15 sections. There are 3 sections per depth. The depths

are 0, .5, 1, 1.5, and 2 inches.

1. Label each section to their corresponding depths with a post-it note.

2. Measure the height of depth using a ruler and place 5 seeds evenly through

the section. Do this in a total of 3 sections.

3. Cover the seeds until the section is full of soil.

4. Repeat steps 1-3 for every height that is measured.

5. Place container under a florescent light bulb.

6. Water each section with 40 mL on the first day.

7. Every day water each section with 15mL.

8. Record the number of days until germination.

9. Create a linear graph depicting each depth’s germination time.

10. Create a bar graph depicting each depth’s germination time.

Experimental Setup:

Raw Data:

Time (days) versus Total Number of Germinated Seeds

Seed Depth (inches)  Day 2.0 1.5 1.0 .5 0.0

1 0 0 0 0 02 0 0 0 0 03 0 0 0 0 04 0 0 0 1 05 0 0 0 3 26 0 0 0 4 27 0 0 0 4 38 0 0 0 4 59 0 0 1 5 5

10 0 0 1 5 511 0 1 2 5 512 0 1 2 5 513 0 2 3 7 614 1 3 4 9 615 1 3 5 9 6

Transformed Data:

Depth Total Number of Germination Percent of Germination0.0 6 40.0%0.5 9 60.0%1.0 5 33.3%1.5 3 20.0%2.0 1 6.6%

Calculations:

Percentage:

Total Number of Germinated Plants/ Total Number of Seeds PlantedEx. 0.5 depth9/15 = .6 or 60%

Discussion:

The hypothesis was not completely proven by this experiment. It was

hypothesized nothing would grow above .5 inches and less than 1.5 inches. It is

surprising to see that the seeds at 0.0, the top of the soil, germinated more than 1.0,1.5,

and 2.0 inches. From the linear graphs and bar graphs we can see that the seeds

germinated less frequently the deeper they were buried. The germination of seeds at 1.0,

1.5, 2.0 depth were 5, 3, 1, respectively. Obviously there is a gradual trend downwards

which tells us that at a certain depth, germination cannot occur. 2 inches below the soil

seems to be the stopping point since only 1 seed out of 15 actually germinated. 0.5

inches, which is supposed to be the optimum depth, proved to be the best depth to bury

the seed.

The first seed that germinated was sowed at 0.5 inches and took only 4 days. The

last seed to germinated was sowed at 2.0 and took 15 days. A whole week after the last

germination was recorded but no other activity occurred and it can be assumed the testing

was complete. Percentage-wise, the 1.5-inch depth germinated 60% of the time. The next

highest percentage occurred at 0.0 depth. In conclusion, sowing an onion seed between

0.0 and 0.5 inched is the optimum depth and anywhere below 1 inch drastically reduces

the percent of germination.

Evaluation:

Errors:

There was probably a sowing distance problem. I noticed that in each of the 15

sections none of the middle seeds germinated. Only the corner seeds actually germinated.

Watering was not completely consistent since 2 days out of the week the seed was not

watered. Temperature was consistent throughout the day but the air conditioner was

turned off during the night and the weekends.

Improvements:

Several tweaks to this experiment can make the results more concrete. The sample

size needs to be increased so that a larger pool of data can give a better percentage of

germination per depth. The sowing distance needs to be increased to a minimum of 2

inches. Temperature must be consistent since this is a large factor in germination.

Works Cited

Habdas, Hannas. "Improving germination and vigour of aged and stored onion seeds by

matriconditioning." IngentaConnect. 21 June 2002.

<http://http://www.ingentaconnect.com/content/klu/11738/2002/00000024/00000

002/00000008?crawler=true>.

Kennell, Holly S. "Seed Germination." Gardening in Western Washington. Washington

State University. <http://http://gardening.wsu.edu/library/vege004/vege004.htm>.

Sell, Randy. "Onion." NDSU. 17 Nov. 1993. University.

<http://http://www.ag.ndsu.edu/pubs/alt-ag/onions.htm>.