LBS 145 Cell and Molecular Biology
"The Carbs"
Combs, E., Mauch C., Smith, K., Wayo D.
Lab T2, Brent and Jeff
Analysis of
Festuca
rubra using
Abstract
Our lab group will
determine whether adding fertilizer to grass plants alters the rate of growth.
Starting with seeds, we will conduct 60 treatments in total using plastic
planters. We’ll plant seeds in each compartment using general plant soil.
Varying the amount of fertilizer administered to the planters, using 0.1-gram,
0.25 grams, 0.5 grams, and 1.0 gram, two 4-pack containers will be our control,
having no fertilizer added. The variation in amount of
fertilizer administered will allow us to see whether the potentially beneficial
effects of fertilizer plateau at some amount. Every treatment including the
control will be watered daily using 25mL of tap water. After two weeks of
fertilization, we’ll test the plants for any increase in height, protein
content, sugar amounts, and photosynthesis. Using
Figure 5: Glucose levels in grass remain about the same despite any increase in fertilizer. Here we increased the fertilizer from 0g to 0.1g, 0.25g, 0.5g, and 1g respectively. Measurements were taken with a diabetes glucose testing device to see if the measurements increased when the fertilizer increased. Three trials at each level of fertilizer and each control were taken and this is the average amount of glucose derived from the three trials.
Discussion
The initial question that we set out to answer was to
find how beneficial fertilizer was on grass plants, or even if it could be
harmful to the plants. The belief that fertilizer helps the
growth of plants is well known, and supported by the research of
VanWieringen et.
al. Despite this research, our
group set out to determine what the fertilizer actually does to the internal
components of the plant, when administered at different quantities.
We also know that nitrogen in the soil helps produce healthy leaves,
phosphorus helps produce a strong root system, and potassium helps a plant to
be, in general, healthier (Kerrigan and Nagel. 1998). We
believed that the fertilizer would increase the grass plants protein content,
glucose content, photosynthetic ability, and height, and therefore the plants
overall health, and then it will also continue to increase those numbers as the
treatments increased with amount of fertilizer. We also know
that over fertilizing can result in nutrient deficiencies because the nutrients
bind to excess elements (Kerrigan and Nagel. 1998 ).
After performing the
The first tests that we performed on the plants were Benedicts and Iodine tests. These gave us solid qualitative data, showing us that the plants definitely had a free Ketone sugar and very low, if any, amount of starch inside of them. Although these tests do not report any actual amount of sugar, it is still important to note that the fertilizer does not hurt the plant and stop it from producing carbohydrates. Benedicts test shows us if there is a free Ketone or Aldehyde group in the solution. If there is a presence of a free sugar group, the reaction will produce a red precipitate (Krha et. al. 14). We found that all treatments tested positive for a free sugar group (Figure 3). When we performed the Iodine test, which tests for the presence of starch in a solution (Krha et al 15), we found that all of the tests were negative, or inconclusive (Figure 2). The Iodine test gives us a dark color for a positive result and no color change for a negative result. From these results, we know that the fertilizer does not effect the plant enough to stop it from performing photosynthesis, and therefore still allowing the grass to create energy to use.
We then preformed the
We then performed the Hills reaction on the grass plants. Hills reaction shows us how the photosynthesis is changed by different variables in plants. It determines the action spectrum of photosynthesis by testing the plant matter with different types of light. The Hills reagent, when reacted with photosynthesis bleaches the solution, making it less absorbent. A lower absorbance indicates that a greater amount of photosynthesis has occurred (Krha et al 126). We found that as we increased the amount of fertilizer, photosynthesis was almost unaffected. All treatments were able to perform photosynthesis more effectively than the control, when given white light. Only the 0.1g treatment was able to perform photosynthesis better than the control when given red light, and no treatment performed photosynthesis better than the control when given blue light (Table 2). These results are not very continuous, making our group believe that no major change to photosynthesis occurs when given fertilizer.
When we tested the plant matter with diabetes monitoring glucose test strips, we found that the control group registered an average glucose reading of 19.66 mg/dl. The 0.1gram fertilizer group showed a reading of 20.33 mg/dl, the 0.25gram showed 21 mg/dl, the 0.5gram showed 21 mg/dl and the 1.0gram treatment showed an average reading of 17 mg/dl (Figure 5). This illustrates to us that the fertilizer actually aided the plants in producing glucose. As with all of the other tests, it also shows that when too much fertilizer is added, it harms the plant.
We also monitored the growth of the grass. We found that the grass given 0.1g or 0.25g fertilizer grew quicker than the grass given no fertilizer. This supports our theory that the fertilizer helps the plant produce more nutrients, aiding it in survival and growth. However, too much fertilizer proved to slow the growth, as seen in the 0.5 gram and 1.0 gram treatments. The control averaged a height of 7cm; while the 0.1gram treatment averaged 9cm and the 0.25gram treatment averaged 10cm (Figure 1). This shows an increase in height in accordance with the fertilizer, but we can not find a direct correlation because of the 0.5gram treatment averaging 5cm and the 1.0g treatment averaging only 4cm. Again, this leads us to believe that too much fertilizer harms the plant growth.
Our results show us that plants given too much fertilizer are actually much less healthy than plants given a lower amount of fertilizer. The plants given low amounts of fertilizer are the healthiest and most nutrient rich of all of the treatments we tested. The 0.25 gram treatment was the healthiest and most nutrient rich of all of the treatments. The lower fertilizer treatments had higher protein, glucose, grew taller, and also looked healthier than the treatments with a higher amount of added fertilizer. The 0.1 gram treatment was the second healthiest, followed by the control, 0.5 gram, and 1.0 gram treatments, respectively. This order shows that the use of fertilizer does benefit plants, but only in low doses. The higher amount of fertilizer causes the nutrients to bind together, prohibiting the plants the use of any of the nutrients from the soil (Kerrigan and Nagel. 1998). For that reason, I believe that the plants in the higher treatments did not grow as well. Even though more fertilizer and nutrients were added, there were fewer nutrients actually there for the absorption by the plants.
One of the biggest problems we found with our experimental method, was that the fertilizer initially blocked the grass seed from sprouting. This allowed the control group and groups with less fertilizer to grow more quickly, allowing them to get a head start on nutrient production, thus, skewing the results. We therefore started the experiment over, allowing all of the treatments to sprout, before applying the first dose of fertilizer. After later finding the results of all of our assays, we recognized that the fertilizer blocking the initial sprouting of the grass is most likely directly correlated to the poor health of the higher dosed fertilized treatments. Another weakness we found with our experiment is that the light boxes we placed the grass plants in may have given different amounts of light to each plant or even an entire treatment. This could have lead our experiment to incomplete or even inaccurate results.
The results of our assays and other experiments was able to verify our hypothesis and predictions that an increased amount of fertilizer is able to increase the amount of protein, glucose, photosynthetic ability and height, in low enough doses. Higher amounts of fertilizer harm all of the tested treatments. The results support the previous research we found, as well as extended the findings to include a correlation between the amount of fertilizer to crop yield and nutritional value of the plants (VanWieringen et. al. 2005). VanWieringen et. al. used a different type of fertilizer that may have released nutrients differently or at slower rates. We originally believed that the more fertilizer added would increase the plants protein, glucose, photosynthesis, and height, but this believe has been proved wrong by our results. We found that when the amount of fertilizer gets too large, the plants will not produce as many nutrients and possibly eventually die.