The Effect of Green Tea and Deionized Water on the Growth Rate and Chlorophyll Concentration of Catharanthus roseus
Brett Niles and Carlin Harkness
Department of Biological Science
SaddlebackCollege
Mission Viejo, CA92692
Green tea has many claims to its health benefits on humans. In this experiment, we tested whether green tea had health benefits to plants. The relationship between green tea, deionized water, and tap water was determined by measuring the growth rates and chlorophyll concentration of three groups of Catharanthus roseus that were watered with the respective mediums. Stem diameters were measured twice a week and chlorophyll concentration was measured by spectrophotometry. The resulting data showed no significant difference in growth rates and chlorophyll concentration data was inconsistent. Therefore, null hypothesis was supported. There were external factors including aphid infestation which might have contributed to our inconsistent results.
Introduction
Extensive research has gone into studying the effects of green tea on humans and animals. However, if out there, official research on the effects of green tea on plants is scarce. Also, there is much media on the health benefits of green tea, mostly concerning the antioxidant properties. Some advocates of green tea make strong claims that it can cure rheumatoid arthritis, reduce body fat, cure gastric ulcers etc. (Johnson 2009). Other research has shown that green tea consumption may reduce the risk of leukemia (Kuo 2008). The consumption of green tea has also been repeatedly shown to play a protective role against liver disease and may lead to a reduced risk of liver disease (Jin 2008). However, research of green tea consumption and cancer is less conclusive. Most studies showed no relationship between green tea consumption and cancer, and few showed that green tea consumption was associated with a decreased cancer risk (Sturgeon 2009). The one thing in common with most studies is that they attribute the beneficial qualities to certain chemicals that are contained in green tea. These chemicals are found in the tannins released from the tea leaves when it is steeped in hot water. Tannins contain polyphenols and flavonoids which are subgroups that contain the antioxidative chemicals that are the source of beneficial health effects. Catechins are one of the classes of flavonoids also called flavin-3-ols. The specific catechin that is known for its potent antioxidant properties is epigallocatechin gallate (EGCG).
Plants along with many other organisms produce free radicals as byproducts or intermediates of metabolic pathways. In plants, photosynthesis is a major producer of free radicals (Uri 1955). In order to counter the free radical intermediates, plants must also produce antioxidants; this is the source of catechins that is acquired from tea when consumed. Therefore, if human consumption of tea possesses many health benefits, then it seems reasonable to presume that it will have similar effects on plants. Our objective was to determine if there was a relationship between plant health and different watering mediums including: green tea, deionized water, and the control group with tap water. We hypothesized that Catharanthus roseus watered with green tea would have improved health and therefore increased growth rates and chlorophyll concentrations compared to Catharanthus roseus watered with tap water and that Catharanthus roseus watered with deionized water would have worse health and therefore decreased growth rates and chlorophyll concentrations compared to Catharanthus roseus watered with tap water.
(The introduction might benefit from starting with information about plants in general, then information about properties in green tea, then benefits of the properties in green tea when consumed by humans, and then tie it all together with your hypothesis)
Methods
We began with young Catharanthus roseus in three groups of ten each: a green tea group, deionized water group, and the control group with tap water. We used soil from same bag and pots, both provided by SaddlebackCollege. The Catharanthus roseus was purchased from Green Thumb International Nursery in crates of 16 plants per. The plants were kept in the greenhouse at SaddlebackCollege in a controlled environment. The experiment lasted for five weeks. Measurements of stem diameter were taken using a digital caliper at location level with the top of the pot. These measurements were taken about twice a week for the duration of the experiment. Also, we noted any plants whose health appeared compromised or if the plant appeared deceased. Each group was watered with the three different mediums: green tea, deionized water, and tap water five days a week for the first week. However, due to soil conditions from this watering frequency being detrimental to the health of the plants and in attempt to use optimal conditions for the experiment, we watered them four days a week for the remainder of the experiment. Each plant received 50 ml of watering medium when watered. An attempt to determine chlorophyll concentration was done with leaf samples taken in the third and fifth week of the experiment. We used methods derived from other research experiments that determined chlorophyll concentration by photospectroscopy (MacKinney 1941, Cate et al. 2003). These leaf samples were then measured out to 0.2 g of leaf material per group and added to 15 ml of 80% acetone solution and left overnight in 4ºC in the dark. Absorbance of the acetone solution containing the chlorophyll was then taken. (what was used to measure the absorbance?)The absorbance was taken for each group first at 940 nm wavelengths as a reference and then at 660 nm. We used ANOVA tests on the stem diameter data and for the chlorophyll concentration absorbance data a ratio was taken to determine chlorophyll content index (CCI).
Results
An analysis of variance (ANOVA) single variable test was performed on the average values of stem diameters for each day of measurement. This first test included the measurements of healthy and unhealthy or dead plants. Green tea did not significantly increase health and deionized water did not significantly decrease health of Catharanthus roseus (p=0.44) compared to the control group. The average stem diameters for each day measured was plotted over time and is shown in figure 1. Then we performed another ANOVA single variable test on the data with the unhealthy and dead plants omitted. Again, green tea did not significantly increase health and deionized water did not significantly decrease health of Catharanthus roseus (p=0.69)
compared to the control group. Also, the average stem diameters for this modified data were plotted over time and are shown in figure 2. The CCI values should be between 1 (no chlorophyll) and 70 (very high chlorophyll), but our CCI values were far above 70. The lowest CCI for any group was 96 and went as high as 1000.
Discussion
We did not find a significant effect of green tea or deionized water on the health of Catharanthus roseus compared to the control group in this experiment. This could be due to many factors. The one that appears most obvious is the infection of several of our plants in the green tea group with aphids. Seven of our plants in the green tea group were infected with aphids by the end of the experiment. This infection spread to the deionized group and tap water group also, but to a less severe degree. By the end of the experiment, only two of the green tea group and seven of the deionized group were still alive. Another factor to consider is the spoiling of the green tea after about a week. The first batch of green tea spoiled after a week, it emitted a foul odor and became turbid. A second batch was made after two weeks; however, it also became spoiled after a week and no more green tea was made after this. Whether or not this could affect the plants is unknown, but should be considered. Furthermore, green tea is richer in chemical constituents compared to tap water. Green tea contains the minerals zinc, manganese, and copper which are essential for plant growth and required in trace amounts. Too much of these minerals can have detrimental effects on plant growth. Furthermore, an abundance of these minerals in the soil can make it more difficult for the plant to take in other needed nutrients. A similar result of the harmful effects of longer exposure to green tea has been observed (Webb 2000). Therefore, green tea may have been beneficial in a shorter duration, but eventually became harmful to the plants in our green tea group.
The chlorophyll concentration data for this experiment was invalid according to the parameters of the resulting values. Our method for determining the chlorophyll concentration may have been incorrect. To produce usable data for chlorophyll concentration, a chlorophyll content meter could be used. The chlorophyll content meter is a handheld device that measures chlorophyll concentration automatically. However, these measuring devices may be out of the budget of some researchers. Therefore, a better method similar to the one used in this experiment may be necessary.
Future research may approach this experiment by watering the green tea group in alternating periods of green tea and tap water. This could possibly utilize the nutrient rich green tea more effectively and not overdose the plants on certain nutrients. Also, measures should be taken to prevent the infection of aphids and use of pesticides of infection occurs.
Literature Cited
Cate, T.M. and Perkins, T.D. 2003, Chlorophyll content monitoring in sugar maple (Acer saccharum). Tree Physiology 23: 1077-1079.
Kuo, YC. (2008). A Population-based, case-control study of green tea consumption and leukemia risk in southwestern taiwan..MEDLINE, Retrieved from doi: 18752033.
Jin, Xi. (2008). Green tea consumptionand liver disease: a systematic review.CLINICAL STUDIES, doi: 10.1111/j.1478-3231.2008.01776.x.
Johnson, Daniel. “Green tea health benefits.” < Published 2009.
MacKinney, G. 1941. The absorption of light by chlorophyll solutions. J. Biol. Chem. 140: 315-322.
Sturgeon, J L. (2009). Efficacy of green tea in the prevention of cancers.Nursing and Health Sciences, 11(436–446).
URI, N. (1955). Free radical intermediates in photosynthesis. BIOCHIM ET BIOPHYS ACTA, 18((2)), 209-215.
Webb, Tracy. “Green tea experiments in lab, clinic yield mixed results.” Journal of the National Cancer Institute, Vol. 92, No. 13, 1038-1039, July 5, 2000.
Review Form
Department of Biological Sciences
SaddlebackCollege, Mission Viejo, CA92692
Author (s)Niles, Harkness
Title: The Effect of Green Tea and Deionized Water on the Growth Rate and Chlorophyll Concentration of Catharanthus roseus
Summary
Summarize the paper succinctly and dispassionately. Do not criticize here, just show that you understood the paper.
Watering the Catharanthus roseus plant with green tea was hypothesized to have an effect on the increase in health compared to watering it with tap water. The radius of the stems and chlorophyll concentrations was used to measure the health of the plants. No significant difference was found. Research shows that significant results were observed when humans and animals consume green tea.
General Comments
Generally explain the paper’s strengths and weaknesses and whether they are serious, or important to our current state of knowledge.
I thought that the idea was okay. It makes sense to want to see if green tea has an effect on the health of plants, seeing that there’s a health advantage to humans and other animals using it. I don’t really think it was very important to our current state of knowledge. Miracle-grow works well enough for the health of plants.
The paper is a little confusing. There are random facts everywhere, but they don’t exactly support anything.
Why was there a group watered with deionized water?
What was the concentration of the green tea solution used to water the plants?
What is a digital caliper?
Would watering the plants with green tea in lower concentrations over the duration of your experiment made a difference?
How long did your experiment last?
What were the temp, humidity, and light-source like in your controlled environment? Would that have made a difference in your results?
Technical Criticism
Review technical issues, organization and clarity. Provide a table of typographical errors, grammatical errors, and minor textual problems. It's not the reviewer's job to copy Edit the paper, mark the manuscript.
This paper was a final versionThis paper was a rough draft
The Paper should be written in 3rd person. No “we” or “our.”