Erica Osiecki
Biology 240W
February 19, 2016

Determining the Metabolism of Gibberellic Acid in Four Genotypes of Brassica Rapa
Abstract:
The goal of this experiment was to evaluate how the plant hormone Gibberellic Acid
(GA3) affects how the four different genotypes in the Brassica rapa plant use the plant hormone in their plant growth. The Brassica rapa plant (dicot) is also known by the trademark name
Wisconsin fast plant because they have been genetically bred to complete their life cycle in approximately one month. This makes it easier to be used in experiments because of their rapid growth which it produces quicker results. The genotypes that were used include a wild type, elongate, petite, and the rosette. There were three treatments used on the four genotypes; water,
Ga3 and Cycocel. These treatments were sprayed two times consistently per day over three weeks for each genotype. Gibberellic acid is a plant hormone which acts as a stimulator for growth and development for the plant. Cycocel however, is a plant inhibitor that inhibits growth and development. This experiment was placed in an apparatus which allows the excess to drain while a wicking system keeps the plants moist. The apparatus was also placed under a light source which was on a limited time cycle. The lights were on for 16 hours each day starting at
7am and were off for 8 hours a day starting at 11pm. Wild type and petite genotypes already contained normal amounts of Ga3, while the elongate over produced Ga3 and rosette under produced Ga3. At the end of the experiment, the genotypes, wild type, petite, and rosette, had the most growth in the Ga3, whereas elongate ended up having the most growth in the control group. In all of the genotypes, Cycocel had growth, but not as much as water and Ga3. Each genotype had a unique way of using Ga3, and by doing so it shows how the plant is using Ga3.
Ga3 is already naturally found in plants and with that being said, this experiment helped show how plants used this natural plant hormone throughout the different genotypes on Brassica rapa.

Erica Osiecki
Biology 240W
February 19, 2016

Introduction:
A hormone is a chemically produced substance, usually in minute amounts, in one part of an organism and transported to another part of the same organism, where it has a specific effect.
Hormones are very important in plant development, and at what rate of growth the plant will have. The six main classes of these hormones are Abscisic Acid, Auxin, Cytokinin, Gibberellic
Acid, Ethylene, and Brassinosteriods. Abscisic acid is a plant inhibitor that causes dormancy, which makes meristems come to a standstill. However, Auxins increase cell elongation and cell division which provide growth of shoot meristems.
Gibberellins are a class of plant hormones responsible for stimulating primary growth in stems and leaves, for breaking bud dormancy and triggering seed germination, and for stimulating fruit development with auxin. Gibberellins can also provide elongation of internodes as well. Ethylene is a naturally found gaseous compound that helps fruits ripen along with the aging of flowers and leaves. Brassinosteriods inhibit root growth and help differentiate xylem, and slow down or even stop leaf abscission.
Gibberellic acid’s effects on plants are stimulating cell growth and cell elongation. These effects are seen in stem growth as well as root growth. Stems and inter nodal lengths can be increased along with root system development. Cell division increases in the production of larger leaves. Gibberellic acid leads to bigger plants with bigger shoots, and leaves in many plants (Brian et al., 9 May 2006). The plant used in the experiment is a brassica rapa, or the
Wisconsin Fast Plant because it has a rapid life cycle around 35-40 days. The genotypes used in this experiment are wild type (control), Petite (dwarf mutant), Elongate (tall mutant), and Rosette

Erica Osiecki
Biology 240W
February 19, 2016

(dwarf mutant). The goal of the experiment was to find how these four genotypes of the
Wisconsin Fast Plant are using Gibberellic acid for their plant growth (Mckeon et al., 2003).
Materials and Methods:
The first part of the experiment started with getting into small lab groups and received a flat of Brassica rapa seedlings that was divided into three sections; water, Ga3, and Cycocel for each group. Each flat was divided into 32 styrofoam sections and each section had all four genotypes such as wild type (WT), Petite (PT), Elongate (EL), and Rosette (RS). The flat also had a water mat included in the setup used to conduct water from the reservoir to the wicks, and the water reservoir contained an anti-algae square that contained copper sulfate to prevent the growth of algae in the reservoir. After receiving the flat of the Brassica rapa seedlings, groups had to pluck the seedling leaves to one plant per cell. After thinning the plants, measurements were taken of the height of all Brassica rapa seedlings with a ruler in millimeters. The measurements were recorded by the height of the seedling within the three sections and what day it was measured and consistently starting from the styrofoam base to the first apical bud. After the measurements were taken, the Brassica rapa flat was then placed underneath a light source that was on a timed schedule. The lights were on for 16 hours each day starting at 7am and then turned off for 8 hours a day starting at 11pm. The members of the group were assigned certain days to measure the Brassica rapa and then apply the treatments. Each section labeled water,
Ga3, and Cycocel were sprayed with the appropriate solution that had the same solution labeled, with 2 sprays inside each genotype. The water only got the water treatment, the Ga3 only got the
Ga3 treatment, and the Cycocel only got the Cycocel treatment. After the six days of recorded data, and on the eighth day the groups came together and measured the plants for the last time,

Erica Osiecki
Biology 240W
February 19, 2016

and recorded the averages each section of their data. The class average of every group’s data was then provided.

Figure 1. Plant Set Up and Treatment

This picture depicts how the Brassica rapa plant was divided into three different sections for each treatment, water, Ga3, and Cycocel which included all four genotypes; Wild Type, Petite,
Elongate, and Rosette.
Results:
Figure 2. Wild Type
The average heights of genotype Wild Type (WT) undergoing the three treatments; water, Ga3, and Cycocel.

Wild Type
Control
GA3
Cycel

1
13.125
14.625
13.375

2
18.75
20.5
17.25

3
21.625
26
17.75

4
26.75
31.75
20.125

5

6

7
28.25
37
18.75

8
31.875
46.5
21.125

Erica Osiecki
Biology 240W
February 19, 2016

Wild Type
50

Height (mm)

40
30
20
10
0
1

2

3

4

5

6

7

8

Days
Control

GA3

Cycocel

Figure 3. Petite
Average heights of the genotype, Petite (PT), undergoing the three treatments; water, Ga3, and
Cycocel.

Petite
Control
GA3
Cycel

1
14.4375
16.625
13.75

2
19.75
22.75
16.75

3
23
26.25
18

4
26
30.5
18.625

5

6

Height (mm)

Petite
45
40
35
30
25
20
15
10
5
0
1

2

3

4

5

Days
Control

GA3

Cycel

6

7

8

7
29.5
37.125
24.375

8
31.5
38.875
18.25

Erica Osiecki
Biology 240W
February 19, 2016

Figure 4. Elongate
The average heights of genotype Elongate (EL), undergoing the three treatments; water, Ga3, and Cycocel.

Elongate
Control
GA3
Cycel

1
30.25
26.625
25.25

2
39.125
35.875
34.375

3
47.625
45.525
37.875

4
53.5
52.125
47.5

5

6

7
64.25
60.875
62.75

8
78.25
76.25
63.625

Height (mm)

Elongate
90
80
70
60
50
40
30
20
10
0
1

2

3

4

5

6

7

8

Days
Control

GA3

Cycel

Figure 5. Rosette
The Average heights of genotype, Rosette (RS), undergoing the three treatments of water, Ga3, and Cycocel.

Rosette
Control
GA3
Cycel

1
0.75
7.875
1.75

2
1.5
11.875
3.125

3
1.75
14
3.375

4
3.5
22.125
5.75

5

6

7
9.25
33.125
8.875

8
1.875
38.5
3.75

Erica Osiecki
Biology 240W
February 19, 2016

Height (mm)

Rosette
45
40
35
30
25
20
15
10
5
0
1

2

3

4

5

6

7

8

Days
Control

GA3

Cycel

Discussion:

The goal of this experiment was to determine how the four genotypes of the Wisconsin Fast
Plant are using Gibberellic Acid to reach different heights during their development. My hypothesis was that the Gibberellic Acid would have the highest growth within all genotypes and would be higher than the control in all three treatments. I hypothesized this because the
Gibberellic Acid stimulates growth and by increasing the Gibberellic Acid content that was already found in the plants, the Gibberellic treatment in all of the four genotypes would have surely been the highest and most successful treatment in stimulating plant growth. I was correct in figures 1, 2, and 4 but however, my hypothesis was incorrect in Figure 3. In figure 3, the control had the highest growth instead of the Gibberellic Acid. I presumed that by having
Gibberellic Acid already in all of the four genotypes naturally, that by increasing the Gibberellic
Acid content with the Gibberellic Acid treatment that all four genotypes would have the highest growth. Erica Osiecki
Biology 240W
February 19, 2016

Wild type and petite had normal amounts of Ga3 already, whereas the elongate over produced Ga3 and rosette under produced Ga3. In the end of the experiment, the genotypes, wild type, petite, and rosette had the most growth in the Ga3, whereas the elongate had the most growth in the control. In all the genotypes, Cycocel had growth but not as drastic as the control or Ga3. Also, in the genotype rosette, the Cycocel had more growth than the control but less than the Ga3 which I did not expect. Overall, each genotype had a unique way of using Ga3 and by doing so it shows how the plant is using Ga3.

Erica Osiecki
Biology 240W
February 19, 2016

Works Cited
Brian, P. W., Elson, G. W., Hemming, H. G., & Radley, M. (2006, May 9). The plant-growthpromoting properties of gibberellic acid, a metabolic product of the fungus gibberella fujikuroi. Retrieved February 19, 2016, from http://onlinelibrary.wiley.com/doi/10.1002/jsfa.2740051210/abstract Marth, P. C., Audia, W. V., & Mitchell, J. W.. (1956). Effects of Gibberellic Acid on Growth and Development of Plants of Various Genera and Species. Botanical Gazette, 118(2),
106–111. Retrieved from http://www.jstor.org/stable/2472972
McKeon, Brian Sr., and Warren, James Jr. 2012. Plant Hormones, Biology 240: Form and
Function, A laboratory Manual (Penn State Erie, The Behrend College).
Rood, B. Stewart, Williams, H. Paul, Pearce, D., Murofushi, N., Mander, M. Lewis, Pharis P.
Richard. (2016). Plant Physiology. A Mutant Gene That Increases Gibberellin Production
In Brassica. 93(3): 1168-1174.