The Effect of Plant Hormones on Barley Height in Unfavorable Soil Profiles

     While conducting this experiment, I was able to apply science concepts I learned in various classes to explain why the different soil profiles allowed the barley to grow to different heights. The data shows that the independent variable, the different soil profiles, did help barley grow in some soil profiles, but not as well in others. To analyze all of the data, I wanted to discuss each one group by group.

     In group 1, the Control group acts as an outlier. The barley didn't grow as much as the other control groups. Over 10 days of data collection, the tallest plant only grew a total of 0.7 cm. This might be attributed to the growth of many barley plants. Group 1 had 4 to 5 seeds that germinated, which was a lot more than the other groups. Since space was limited, the water and butyric acid had to be shared against many plants, so each plant grew to a smaller height. Although, it's still a good sign that just 10 mL of butyric acid at a density of 4g/L per day was able to support barley growth, no matter the amount of growth. The Haiti group grew incredibly well, just like those in groups 2 and 3. Over 10 days of collection, the barley plant grew 4.1 cm, which was very good. The Kenya group's tallest plant also grew 5.4 cm over 10 days, which was even better than the Haiti group. Finally, the Australia group grew incredibly poorly, with a net loss of 0.5 cm because the plant shriveled up. These groups (except for the control group) mostly show the average trend in data for the other groups as well.

     In group 2, the Control group grew as predicted. Over the course of the experiment, the tallest plant grew 3.1 cm, which was more on par with group 3's result of its control group. The Haiti group also grew extremely well; it went from ungerminated to 8.4 cm in 10 days. The Kenya group grew 4.4 cm over data collection, which was still exemplary. And, as predicted, the Australia group did poorly, losing 0.1 cm over the course of the experiment. 

     Finally, group 3 followed the precedents set by groups 1 and 2. The Control Group grew 2.4 cm over 10 days, which was a little lower than group 2 but can be explained under circumstances similar to those that plagued group 1's Control group. The Haiti group kept up its stellar growth, at 5.1 cm over data collection. This particualar Kenya group earned the award for most growth; its tallest plant grew 11.2 cm over 10 days; that was more than 1 cm per day. And, as seen in the other groups, the Australia group lost 1.3 cm. I analyzed the trends between each soil profile and explained my observations and the data in the next paragraph. 

     Each soil profile had certain trends that I observed, regardless of what group they were part of (1, 2, or 3). For the control group, they had a lower average growth across the three groups than the averages of Haiti and Kenya. This can be explained because I took the tallest height in my data collection, but all 3 control groups had the most plants that germinated. This shows that the control group soil can be used to raise the most barley, but it will take longer to grow as tall as the barley in some other soil profiles. If there was more space available, it would seem like the Control group soil, which is rich in clay and nutrients, would increase the quality and quantity of barley when butyric acid was applied to it. For the Haiti and Kenya groups, their high rate of growth is mainly attributable to the science of the nitrogen cycle. In the nitrogen cycle, bacteria fixes atmospheric nitrogen into nutrients and ammonia, which plants can use to grow. Barley is no exception, and after research, it shows that rooting hormone, such as the one I used, promotes the growth of this bacteria. Since both soil profiles were similar in that they were soil that lacked nutrients, the bacteria must have returned the nutrients to the soil for the barley to use. The tall height was also caused because only 1 or 2 seeds germinated in all of the Haiti and Kenya dishes. Without many plants competing for butyric acid and water, they were able to grow taller. Finally, the Australian soil profile grew so poorly mainly because there was not much soil at all. Most of it was pure sand and the only reason any seeds even germinated was because I put in small amounts of soil on top of each seed when I planted. The sandy, pourous soil was not enough to support growth because the soil couldn't retain water or nutrients, which was why the plants started shriveling and dying before the data collection even finished. 

     A possible source of error was present in the design of my experiment. The most prevalent error was the equal watering of all soil profiles. Since some soil profiles, such as the sand, were pourous, the aqueous solution of butyric acid wasn't fully absorbed by the barley roots. But I could not water more than the alloted 10 mL per day because that would introduce too many variables into the experiment.