1. Part I: Effects of Soil vs. Agar on Germination
The Growth of Shoots in Arabidopsis Plants in Soil and Agar Leah Odom, Gordon Gulledge, Becka Dunbar, and Becky Gardner Wofford College
Introduction
Summary
It was found that Arabidopsis seedlings have a longer shoot when grown in soil instead of agar. On average, the seedlings grown in soil measured around 7mm while the seedlings grown in agar averaged only 4mm.
Since most plants are already planted in soils and not in agar dishes, we think that planting the seeds in soil will speed up the germination time. Many times, in research labs, Arabidopsis’ are grown in agar. However, a study done by Robert Eddy and Daniel Hahn from Purdue University showed that Arabidopsis plants can be grown in soil. Our experiment is whether soil or agar would be produce longer shoot lengths in the Arabidopsis.
Status of Hypothesis
These results support the hypothesis that Arabidopsis seedlings planted in soil grow significantly longer shoots after two weeks than seedlings planted in agar.
Hypothesis
Discussion
If Arabidopsis seeds are planted in soil, the shoot will be longer than if planted on agar plates.
Arabidopsis plants are found in a wide variety of environments and conditions. Planting Arabidopsis seedlings in a laboratory limits the conditions of growth and does not represent a natural environment. By planting in seedlings in soil, you are able to simulate natural environmental conditions. An advantage of planting the seedlings in agar is being able to observe the full growth of the plants. These results show that soil provides better conditions for Arabidopsis shoot growth. After comparing the results of shoot growth in agar and soil, they support our original hypothesis proving that the shoot lengths of the Arabidopsis seedlings grown in soil are significantly longer than those grown in the agar.
This experiment was fairly simplistic, only observing the germination percentage and the average shoot length. In future experiments, it would be more beneficial to incorporate different temperatures or light cycles to simulate varied environments. This would allow the scientist to more accurately determine the causes of accelerated shoot length growth.
Methods
The graph above shows the shoot length (in mm) of Arabidopsis plants, after two weeks, grown in soil and agar. The graph proves that the shoot length is significantly longer in the seedlings planted in soil. It can be said that the treatment of the seedlings has a large impact on how much they will grow.
Ten Arabidopsis thaliana seeds of each Ecotype Columbia were planted on the upper edge of the agar in each of five different small cups. Each cup was designated by a letter and each seed in the cup was given a number so that we were able to keep track of each plant.
Cups covered with saran wrap were placed in a vertical position underneath florescent lighting on a 16 hour light: 8 hour dark photoperiod. This was the control group in the experiment.
Ten Arabidopsis seeds were also placed in each of 5 soil filled cups covered in saran wrap with the exact same photoperiod.
The humidity levels of both the soil and the agar plates were kept as similar as possible by covering each of the cups with saran wrap.
The seeds were observed once a week on Wednesday over a period of two weeks. On the first Week, we recorded germination rates of the plants and on the second week we measured the shoot length of each of the 100 plants.
After measuring the shoot length and recording the germination rates, we were able to use the SPSS program to run analysis of our experiment.
Results
Part I: Effects of Soil vs. Agar on Germination
Seeds germinated equally well on soil and in agar. (P=0.176, Fischer’s exact test) (data not shown). We have no statistically significant evidence that germination rate is associated with treatment.
Part II: Effects of Soil vs. Agar on Shoot Length
Arabidopsis grown in soils shoots grew significantly longer than those grown on agar. (P=.000, ANOVA, Fdf=1,72=31.16)
Acknowledgements
The authors are indebted to G.R.. Davis for help with data collection and to C.L. Abercrombie for help with statistical analysis.