Gibberellic acid Lab - Grade: A PDF

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The Effect of Gibberellic Acid on The Growth of Dwarf Corn Plants By: Jasmine Aseme Professor Rebecca Silady 14 November 2019.

INTRODUCTION Hormones are chemicals produced in low concentrations within the plant that regulate growth and development. Hormones can either function together or separately and some hormones have different effects in different plants. There are five major plant hormones and gibberellic acid is one of these major hormones. Gibberellic acid is a plant hormone that is located in the meristem of plants. The effects of gibberellic acid on plants include promoting stem and cell elongation, growth, and fruit ripening. Gibberellic acid has also been discovered to play a role in leaf differentiation and also shape development of the plant (Fleet et al 2005). The growth of fruit and also the size and weight of the fruit from plants are influenced by the action of gibberellic acid (Kukali et al 2014). The d5 mutation in plants is present in a gene involved in the synthesis of gibberellic acid. Evert et al. (2013) stated that when a plant is homozygous recessive for this gene, they are unable to synthesize gibberellic acid properly. This results in the plant being unable to grow to its normal height. The purpose of the experiment was to investigate the effect of gibberellic acid on the growth of dwarf corn plants.

HYPOTHESIS The null hypothesis of the experiment is that the addition of gibberellic acid will have no effect on the growth of dwarf corn plants. The alternate hypothesis is that the addition of gibberellic acid will lead to an increase in growth of dwarf corn plants. METHODS On day one, three dwarf corn plants were obtained and each of the plants were labelled: water, 0.1ug/ul GA and 1.0ug/ul GA. The heights of all three plants were then measured in centimeters from the bottom of the plant where it emerges from the soil to the tip of the longest leaf of the plant. The measurements of all three plants were recorded. Using a transfer pipette, one drop of the appropriate solution containing 0.05% tween was dropped into the center whorl of each labelled plant. 0.05% tween was present in the solution of gibberellic acid to remove the waxy layer on the corn plants and allow gibberellic acid to go into the plant. Tween was also used in the control to determine if tween would impact the experiment. On day eight, the height of each plant was measured again and recorded. RESULTS Plant

Concentration of Gibberellic acid (ug/ul)

Plant 1

Final Height: Day 8 (cm)

Change in height from day 1-5 (cm)

0.0 (water)

Initial Height: Day 1 (cm) 20.5

20.5

0

Plant 2

0.1

19.0

29.0

10

Plant 3

1.0

17.0

24.7

7.7

Table 1: Table showing the changes over time in the height measurements of three dwarf corn plants with addition of varying concentrations of gibberellic acid.

Graph Comparing The Average Heights of Dwarf Corn Plants Under Varying Treatments of Gibberellic Acid Over Time 80 70 60

Averageheight (cm)

50 40 30 20 10 0 DAY 1

1.0 ug/ul GA

DAY 8

Figure 1: Line graph comparing the average heights of dwarf corn plants under three varying concentrations of gibberellic acid over time.

From the class data obtained on day one, the average height of the plants treated with water, 0.1ug/ul GA and 1.0 ug/ul GA were 15.9 +/- 0.6 cm, 15.7 +/- 0.7 cm and 15.7 +/- 0.6 cm respectively (Figure 1) From the class data obtained on day eight, the average height of the plants treated with water, 0.1ug/ul GA and 1.0 ug/ul GA were 18.2 +/- 0.6 cm, 23.7 +/- 1.2 cm and 26.5 +/- 1.1 cm respectively (Figure 1) For the day one measurements, the p-values obtained using a t-test for water vs 0.1ug/ul GA, water vs 1.0ug/ul GA and 0.1ug/ul GA vs 1.0ug/ul GA were 0.84098439, 0.8532516 and 0.97317804 respectively. The p-values obtained for the day eight measurements were 0.00026768, 0.000000369142 and 0.08515008 for water, 0.1ug/ul GA and 1.0 ug/ul GA respectively.

DISCUSSION AND CONCLUSION The purpose of the experiment was to investigate the effect of gibberellic acid on the growth of dwarf corn plants. Based on the results obtained, the null hypothesis that gibberellic acid has no effect on dwarf corn plants is rejected and the alternate hypothesis that gibberellic acid will lead to an increase in growth, is accepted. The results showed that the average heights of all the plants had increased on day eight and the plants that were treated with the highest concentration of gibberellic acid grew the most compared to the other plants. On the other hand, the control plants that were treated with no gibberellic acid but just water had the lowest increase in growth. Based on the results obtained on Day 8 for water vs 0.1 ug/ul GA and water vs 1.0ug/ul GA, the p-values were less than the  value of 0.05 which means that the two compared samples

are statistically different. The p-value obtained on Say 8 for 0.1 ug/ul GA vs 1.0 ug/ul GA was greater than 0.05 and determined to be insignificant. Possible errors that might have occurred during the experiment include recording incorrect height measurements for the plants, using more than one drop of the gibberellic acid, using a solution of gibberellic acid that did not contain tween and not putting the drop of gibberellic acid in the central whorl of the plant which would all result in inaccurate results. A future experiment I would recommend is testing the effect of gibberellic acid on other plants to compare and contrast their rate of growth to that of the dwarf corn plants used in this experiment. I would also recommend testing the effect of other growth hormones on dwarf corn plants to investigate if they would lead to a growth in height. The results of this experiment are significant in order to understand how the gene for d5 mutation affects plant growth and to understand how gibberellic acid works to counter the effect of the gene.

LITERATURE CITED Evert RF, Eichhorn SE, Perry JB, Raven PH. Laboratory topics in botany: to accompany Evert and Eichhorn Biology of plants. 8th ed. New York, NY: W. H. Freeman and Company; 2013. Fleet, C.M., Sun, T.P. 2005. A DELLAcate balance: The role of gibberellin in plant morphogenesis. Current Opinion in Plant Biology, 8(1), 77–85. doi: 10.1016/j.pbi.2004.11.015 Kukali, E.,Thomaj, T., Mane, E. 2014. The Effect of Gibberellins on the Production Increase and Quality Improvements of Grape. Albanian Journal of Agricultural Sciences, 13(4), 47-50....